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In organic chemistry , the Mannich reaction is a three-component organic reaction that involves the amino alkylation of an acidic proton next to a carbonyl ( C=O ) functional group by formaldehyde ( H−CHO ) and a primary or secondary amine ( −NH 2 ) or ammonia ( NH 3 ). [ 1 ] The final product is a β-amino-carbonyl compound also known as a Mannich base . Reactions between aldimines and α-methylene carbonyls are also considered Mannich reactions because these imines form between amines and aldehydes .
The reaction is named after Carl Mannich . [ 2 ] [ 3 ]
The Mannich reaction starts with the nucleophilic addition of an amine to a carbonyl group followed by dehydration to the Schiff base . The Schiff base is an electrophile which reacts in a second step in an electrophilic addition with an enol formed from a carbonyl compound containing an acidic alpha-proton. The Mannich reaction is a condensation reaction . [ 4 ] : 140
In the Mannich reaction, primary or secondary amines or ammonia react with formaldehyde to form a Schiff base. Tertiary amines lack an N–H proton and so do not react. The Schiff base can react with α-CH-acidic compounds ( nucleophiles ) that include carbonyl compounds, nitriles , acetylenes , aliphatic nitro compounds , α-alkyl- pyridines or imines . It is also possible to use activated phenyl groups and electron-rich heterocycles such as furan , pyrrole , and thiophene . Indole is a particularly active substrate; the reaction provides gramine derivatives.
The Mannich reaction can be considered to involve a mixed- aldol reaction , dehydration of the alcohol, and conjugate addition of an amine ( Michael reaction ) all happening in " one-pot ". Double Mannich reactions can also occur.
The mechanism of the Mannich reaction starts with the formation of an iminium ion from the amine and formaldehyde. [ 4 ] : 140
The compound with the carbonyl functional group (in this case a ketone ) will tautomerize to the enol form, after which it attacks the iminium ion.
On methyl ketones, the enolization and the Mannich addition can occur twice, followed by an β-elimination to yield β-amino enone derivatives. [ 5 ] [ 6 ]
( S )-proline catalyzes an asymmetric Mannich reaction. It diastereoselects the syn adduct , with greater effect for larger aldehyde substituents; and enantioselects the ( S , S ) adduct. [ 7 ] A substituted proline can instead catalyze the ( R , S ) anti adduct. [ 8 ]
The Mannich reaction is used in many areas of organic chemistry, Examples include: | https://en.wikipedia.org/wiki/Mannich_reaction |
The Manning formula or Manning's equation is an empirical formula estimating the average velocity of a liquid in an open channel flow (flowing in a conduit that does not completely enclose the liquid). However, this equation is also used for calculation of flow variables in case of flow in partially full conduits , as they also possess a free surface like that of open channel flow. All flow in so-called open channels is driven by gravity .
It was first presented by the French engineer Philippe Gaspard Gauckler [ fr ] in 1867, [ 1 ] and later re-developed by the Irish engineer Robert Manning in 1890. [ 2 ] Thus, the formula is also known in Europe as the Gauckler–Manning formula or Gauckler–Manning–Strickler formula (after Albert Strickler ).
The Gauckler–Manning formula is used to estimate the average velocity of water flowing in an open channel in locations where it is not practical to construct a weir or flume to measure flow with greater accuracy. Manning's equation is also commonly used as part of a numerical step method, such as the standard step method , for delineating the free surface profile of water flowing in an open channel. [ 3 ]
The Gauckler–Manning formula states:
where:
Note: the Strickler coefficient is the reciprocal of Manning coefficient: Ks =1/ n , having dimension of L 1/3 /T and units of m 1/3 /s; it varies from 20 m 1/3 /s (rough stone and rough surface) to 80 m 1/3 /s (smooth concrete and cast iron).
The discharge formula, Q = A V , can be used to rewrite Gauckler–Manning's equation by substitution for V . Solving for Q then allows an estimate of the volumetric flow rate (discharge) without knowing the limiting or actual flow velocity.
The formula can be obtained by use of dimensional analysis . In the 2000s this formula was derived theoretically using the phenomenological theory of turbulence . [ 4 ] [ 5 ]
The hydraulic radius is one of the properties of a channel that controls water discharge. It also determines how much work the channel can do, for example, in moving sediment. All else equal, a river with a larger hydraulic radius will have a higher flow velocity, and also a larger cross sectional area through which that faster water can travel. This means the greater the hydraulic radius, the larger volume of water the channel can carry.
Based on the 'constant shear stress at the boundary' assumption, [ 6 ] hydraulic radius is defined as the ratio of the channel's cross-sectional area of the flow to its wetted perimeter (the portion of the cross-section's perimeter that is "wet"):
where:
For channels of a given width, the hydraulic radius is greater for deeper channels. In wide rectangular channels, the hydraulic radius is approximated by the flow depth.
The hydraulic radius is not half the hydraulic diameter as the name may suggest, but one quarter in the case of a full pipe. It is a function of the shape of the pipe, channel, or river in which the water is flowing.
Hydraulic radius is also important in determining a channel's efficiency (its ability to move water and sediment ), and is one of the properties used by water engineers to assess the channel's capacity .
The Gauckler–Manning coefficient, often denoted as n , is an empirically derived coefficient, which is dependent on many factors, including surface roughness and sinuosity . When field inspection is not possible, the best method to determine n is to use photographs of river channels where n has been determined using Gauckler–Manning's formula.
The friction coefficients across weirs and orifices are less subjective than n along a natural (earthen, stone or vegetated) channel reach. Cross sectional area, as well as n , will likely vary along a natural channel. Accordingly, more error is expected in estimating the average velocity by assuming a Manning's n , than by direct sampling (i.e., with a current flowmeter ), or measuring it across weirs, flumes or orifices .
In natural streams, n values vary greatly along its reach, and will even vary in a given reach of channel with different stages of flow. Most research shows that n will decrease with stage, at least up to bank-full. Overbank n values for a given reach will vary greatly depending on the time of year and the velocity of flow. Summer vegetation will typically have a significantly higher n value due to leaves and seasonal vegetation. Research has shown, however, that n values are lower for individual shrubs with leaves than for the shrubs without leaves. [ 7 ] This is due to the ability of the plant's leaves to streamline and flex as the flow passes them thus lowering the resistance to flow. High velocity flows will cause some vegetation (such as grasses and forbs) to lay flat, where a lower velocity of flow through the same vegetation will not. [ 8 ]
In open channels, the Darcy–Weisbach equation is valid using the hydraulic diameter as equivalent pipe diameter.
It is the only best and sound method to estimate the energy loss in human made open channels. For various reasons (mainly historical reasons), empirical resistance coefficients (e.g. Chézy, Gauckler–Manning–Strickler) were and are still used. The Chézy coefficient was introduced in 1768 while the Gauckler–Manning coefficient was first developed in 1865, well before the classical pipe flow resistance experiments in the 1920–1930s. Historically both the Chézy and the Gauckler–Manning coefficients were expected to be constant and functions of the roughness only. But it is now well recognised that these coefficients are only constant for a range of flow rates. Most friction coefficients (except perhaps the Darcy–Weisbach friction factor) are estimated 100% empirically and they apply only to fully rough turbulent water flows under steady flow conditions.
One of the most important applications of the Manning equation is its use in sewer design. Sewers are often constructed as circular pipes. It has long been accepted that the value of n varies with the flow depth in partially filled circular pipes. [ 9 ] A complete set of explicit equations that can be used to calculate the depth of flow and other unknown variables when applying the Manning equation to circular pipes is available. [ 10 ] These equations account for the variation of n with the depth of flow in accordance with the curves presented by Camp. | https://en.wikipedia.org/wiki/Manning_formula |
Mannitol hexanitrate is a powerful explosive . Physically, it is a powdery solid at normal temperature ranges, with density of 1.73 g/cm 3 . The chemical name is hexanitromannitol and it is also known as nitromannite , MHN , and nitromannitol , and by the trademarks Nitranitol and Mannitrin . It is more stable than nitroglycerin , and it is used in detonators .
Mannitol hexanitrate is a secondary explosive formed by the nitration of mannitol , a sugar alcohol . The product is used in medicine as a vasodilator and as an explosive in blasting caps. Its sensitivity is high, particularly at high temperatures (> 75 °C) where it is slightly more sensitive than nitroglycerine. Nitromannite is a class B explosive.
The production of pure MHN is not a trivial task, since most preparations will yield a mixture of MHN and lower esters (pentanitrate and lower). [ 1 ]
This explosives -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Mannitol_hexanitrate |
Manolis Kellis ( Greek : Μανώλης Καμβυσέλλης ; born 1977) is a professor of Computer Science and Computational Biology at the Massachusetts Institute of Technology (MIT) and a member of the Broad Institute of MIT and Harvard . [ 3 ] He is the head of the Computational Biology Group at MIT [ 4 ] and is a Principal Investigator in the Computer Science and Artificial Intelligence Lab (CSAIL) at MIT. [ 5 ]
Kellis is known for his contributions to genomics , human genetics , epigenomics , gene regulation , genome evolution , disease mechanism , and single-cell genomics . He co-led the NIH Roadmap Epigenomics Project [ 6 ] effort to create a comprehensive map of the human epigenome, [ 7 ] [ 8 ] [ 9 ] the comparative analysis of 29 mammals to create a comprehensive map of conserved elements in the human genome, [ 10 ] [ 11 ] the ENCODE , GENCODE , and modENCODE projects to characterize the genes, non-coding elements, and circuits of the human genome and model organisms. [ 12 ] [ 13 ] [ 14 ] A major focus of his work is understanding the effects of genetic variations on human disease, [ 15 ] with contributions to obesity , [ 16 ] [ 17 ] [ 18 ] diabetes , [ 19 ] Alzheimer's disease , [ 20 ] [ 21 ] [ 22 ] schizophrenia , [ 23 ] and cancer . [ 24 ]
Kellis was born in Greece, moved with his family to France when he was 12, and came to the U.S. in 1993. [ 25 ] He obtained his PhD from MIT, where he worked with Eric Lander , founding director of the Broad Institute, and Bonnie Berger , professor at MIT [ 26 ] and received the Sprowls award for the best doctorate thesis in Computer Science, [ 27 ] and the first Paris Kanellakis graduate fellowship. [ 28 ] Prior to computational biology, he worked on artificial intelligence, sketch and image recognition, robotics, and computational geometry, at MIT and at the Xerox Palo Alto Research Center . [ 26 ]
As of April 2025, Manolis Kellis has authored 250 journal publications [ 29 ] that have been cited 190,000 times. [ 1 ] He has helped direct several large-scale genomics projects, including the Roadmap Epigenomics project, [ 30 ] [ 7 ] the Encyclopedia of DNA Elements (ENCODE) project, [ 31 ] the Genotype Tissue-Expression (GTEx) project. [ 15 ]
Kellis started comparing the genomes of yeast species as an MIT graduate student. As part of this work, which was published in Nature in 2003, [ 32 ] he developed computational methods to pinpoint patterns of similarity and difference between closely related genomes. The goal was to develop methods for understanding genomes with a view to apply them to the human genome.
He turned from yeast to flies and ultimately to mammals, comparing multiple species to explore genes, their control elements, and their deregulation in human disease. [ 33 ] Kellis led several comparative genomics projects in human, [ 33 ] mammals, [ 34 ] [ 10 ] flies, [ 35 ] [ 36 ] and yeast. [ 37 ]
Kellis co-led the NIH government-funded project to catalogue the human epigenome. He said during an interview with MIT Technology Review [ 33 ] “If the genome is the book of life, the epigenome is the complete set of annotations and bookmarks.” [ 33 ] His lab now uses this map to further the understanding of fundamental processes and disease in humans.
Kellis and colleagues used epigenomic data to investigate the mechanistic basis of the strongest genetic association with obesity, published in the New England Journal of Medicine . [ 16 ] They showed that this mechanism operates in the fat cells of both humans and mice and detailed how changes within the relevant genomic regions cause a shift from dissipating energy as heat ( thermogenesis ) to storing energy as fat. [ 18 ] A full understanding of the phenomenon may lead to treatments for people whose 'slow metabolism' cause them to gain excessive weight. [ 17 ]
Kellis, Li-Huei Tsai , and others at MIT used epigenomic markings in human and mouse brains to study the mechanisms leading to Alzheimer ’s disease, published in Nature in 2015. [ 20 ] They showed that immune cell activation and inflammation, which have long been associated with the condition, are not simply the result of neurodegeneration, as some researchers have argued. Rather, in mice engineered to develop Alzheimer’s-like symptoms, they found that immune cells start to change even before neural changes are observed. [ 21 ]
The Kellis Lab has profiled a large number of human post-mortem brains at single-cell resolution, studying inter-individual variation associated with genetic differences and disease phenotypes, including the first single-cell transcriptomic analysis of Alzheimer's disease (Nature, 2019).
Kellis is a member of the Genotype-Tissue Expression (GTEx) project that seeks to elucidate the basis of disease predisposition. It is an NIH-sponsored project that seeks to characterize genetic variation in human tissues with roles in diabetes, heart disease, and cancer. [ 15 ]
Kellis is also a Principal Investigator of the enhancing GTEx (eGTEx) consortium, studying epigenomic changes of regulatory elements and epitranscriptomic changes of RNA transcripts across multiple human tissues. [ 38 ]
To date, his lab has developed specific domain expertise in obesity, [ 17 ] diabetes, [ 19 ] Alzheimer's disease, [ 20 ] schizophrenia, [ 23 ] heart disease, [ 39 ] ALS and FTLD , [ 40 ] and cancer. [ 24 ]
In addition to his research, Kellis co-taught for several years MIT's required undergraduate introductory algorithm courses 6.006: Introduction to Algorithms and 6.046: Design and Analysis of Algorithms [ 41 ] [ 42 ] with Profs. Ron Rivest , Erik Demaine , Piotr Indyk , Srinivas Devadas and others.
He is also teaching a computational biology course at MIT, titled "Computational Biology: Genomes, Networks, Evolution." [ 43 ] The course (6.047/6.878) is geared towards advanced undergraduate and early graduate students, seeking to learn the algorithmic and machine learning foundations of computational biology, and also be exposed to current frontiers of research in order to become active practitioners of the field. [ 44 ] He started 6.881: Computational Personal Genomics: Making sense of complete genomes , and 6.883/9.S99: Neurogenomics: Computational Molecular Neuroscience This course is aimed at exploring the computational challenges associated with interpreting how sequence differences between individuals lead to phenotypic differences such as gene expression, disease predisposition, or response to treatment. [ 45 ]
Kellis received the US Presidential Early Career Award for Scientists and Engineers (PECASE), [ 46 ] the National Science Foundation CAREER award , [ 47 ] a Sloan Research Fellowship , [ 48 ] the Gregor Mendel Medal for Outstanding Achievements in Science by the Mendel Lectures committee, the Athens Information Technology (AIT) Niki Award for Science and Engineering, [ 49 ] the Ruth and Joel Spira Teaching award, [ 50 ] and the George M. Sprowls Award for the best Ph.D. thesis in Computer Science at MIT. [ 27 ] He was named as one of Technology Review's Top 35 Innovators Under 35 for his research in comparative genomics [ 51 ] | https://en.wikipedia.org/wiki/Manolis_Kellis |
Manteia Predictive Medicine S.A. (initially incorporated under the name "GenInEx S.A.") was a start-up company created in November 2000 as a spin-off of Serono , a Swiss-based biotechnology company, now part of Merck-Serono, by private founders. [ 1 ] Its aim was to provide preventive and curative treatment guidelines for common and complex diseases. [ 2 ] These guidelines were envisaged as composed of two parts:
The company was basing its strategy on the development of so-called "DNA colony sequencing" technology (now commercialized by Illumina ), its proprietary massive parallel sequencing [ 3 ] technology whose development had been initiated in late 1996 at Glaxo-Welcome's Geneva Biomedical Research Institute (GBRI), by Pascal Mayer [ 4 ] and Laurent Farinelli. This work has been protected by several patents and patents applications, [ 5 ] publications [ 6 ] [ 7 ] and was discussed in presentations at international conferences from 1998 to 2001. [ 8 ] [ 9 ] [ 10 ] [ 11 ] [ 12 ]
By the end of 2003, while the company was progressing along its plans towards realizing an industrial instrument capable of sequencing a complete human genome in approximately 24 hours, strategic considerations led the main shareholder ( Serono ) to sell Manteia's colony DNA sequencing technology to UK based Solexa Ltd, now part of Illumina (company) . [ 13 ] [ 14 ] | https://en.wikipedia.org/wiki/Manteia_Predictive_Medicine |
Mantle oxidation state (redox state) applies the concept of oxidation state in chemistry to the study of the Earth's mantle . The chemical concept of oxidation state mainly refers to the valence state of one element , while mantle oxidation state provides the degree of decreasing or increasing valence states of all polyvalent elements in mantle materials confined in a closed system. The mantle oxidation state is controlled by oxygen fugacity and can be benchmarked by specific groups of redox buffers .
Mantle oxidation state changes because of the existence of polyvalent elements (elements with more than one valence state, e.g. Fe , Cr , V , Ti , Ce , Eu , C and others). Among them, Fe is the most abundant (≈8 wt% of the mantle [ 2 ] ) and its oxidation state largely reflects the oxidation state of mantle. Examining the valence state of other polyvalent elements could also provide the information of mantle oxidation state.
It is well known [ clarification needed ] that the oxidation state can influence the partitioning behavior of elements [ 3 ] [ 4 ] and liquid water [ 5 ] between melts and minerals, the speciation of C-O-H-bearing fluids and melts, [ 6 ] as well as transport properties like electrical conductivity and creep. [ 5 ]
The formation of diamond requires both reaching high pressures and high temperatures and a carbon source. The most common carbon source in the Earth's lower mantle is not elemental carbon, hence redox reactions need to be involved in diamond formation. Examining the oxidation state aids in predicting the P-T conditions of diamond formation and can elucidate the origin of deep diamonds. [ 7 ]
Mantle oxidation state can be quantified as the oxygen fugacity ( f O 2 {\displaystyle fO_{2}} ) of the system within the framework of thermodynamics . A higher oxygen fugacity implies a more oxygen-rich and more oxidized environment. At each given pressure - temperature conditions, for any compound or element M that bears the potential to be oxidized by oxygen [ 8 ] [ 9 ]
M + x 2 O 2 ⇌ M O x {\displaystyle M+{\frac {x}{2}}O_{2}\rightleftharpoons MO_{x}}
For example, if M is Fe, the redox equilibrium reaction can be Fe+1/2O 2 =FeO; if M is FeO, the redox equilibrium reaction can be 2FeO+1/2O 2 =Fe 2 O 3 .
Gibbs energy change associated with this reaction is therefore
Δ G = G ( M O x ) − G ( M ) = x 2 R T l n f O 2 {\displaystyle \Delta G=G(MO_{x})-G(M)={\frac {x}{2}}RTlnfO_{2}}
Along each isotherm , the partial derivation of ΔG with respect to P is ΔV ,
∂ Δ G ∂ P | T = Δ V {\displaystyle {\frac {\partial \Delta G}{\partial P_{|T}}}={\Delta V}} . [ citation needed ]
Combining the 2 equations above,
∂ ( l n f O 2 ) ) ∂ P | T = 2 x R T Δ V {\displaystyle {\frac {\partial (lnfO_{2}))}{\partial P|_{T}}}={\frac {2}{xRT}}\Delta V} .
Therefore,
l o g f O 2 ( P ) = l o g f O 2 ( 1 b a r ) + ( 0.8686 R T ) ∫ 1 b a r P Δ V d P {\displaystyle logfO_{2}(P)=logfO_{2}(1bar)+({\frac {0.8686}{RT}})\int _{1bar}^{P}\Delta VdP} (note that ln (e as the base) changed to log (10 as the base) in this formula.
For a closed system, there might exist more than one of these equilibrium oxidation reactions, but since all these reactions share a same f O 2 {\displaystyle fO_{2}} , examining one of them would allow extraction of oxidation state of the system.
The physics and chemistry of mantle largely depend on pressure . As mantle minerals are compressed, they are transformed into other minerals at certain depths. Seismic observations of velocity discontinuities and experimental simulations on phase boundaries both verified the structure transformations within the mantle. As such, the mantle can be further divided into three layers with distinct mineral compositions.
Since mantle mineral composition changes, the mineral hosting environment for polyvalent elements also alters. For each layer, the mineral combination governing the redox reactions is unique and will be discussed in detailed below.
Between depths of 30 and 60 km, oxygen fugacity is mainly controlled by Olivine - Orthopyroxene - Spinel oxidation reaction.
6 F e 2 S i O 4 + O 2 ⇌ 3 F e 2 S i 2 O 6 + 2 F e 3 O 4 {\displaystyle 6Fe_{2}SiO_{4}+O_{2}\rightleftharpoons 3Fe_{2}Si_{2}O_{6}+2Fe_{3}O_{4}}
Under deeper upper mantle conditions, Olivine - Orthopyroxene - Garnet oxygen barometer [ 11 ] is the redox reaction that is used to calibrate oxygen fugacity. 4 F e 2 S i O 4 + 2 F e S i O 3 + O 2 ⇌ 2 F e 3 2 + F e 2 3 + S i 3 O 12 {\displaystyle 4Fe_{2}SiO_{4}+2FeSiO_{3}+O_{2}\rightleftharpoons 2Fe_{3}^{2+}Fe_{2}^{3+}Si_{3}O_{12}}
In this reaction, 4 mole of ferrous ions were oxidized to ferric ions and the other 2 mole of ferrous ions remain unchanged.
Garnet-Garnet [ 12 ] reaction can be used to estimate the redox state of transition zone .
2 C a 3 A l 2 S i 3 O 12 + 4 3 F e 3 A l 2 S i 3 O 12 + 2.5 M g 4 S i 4 O 12 + O 2 ⇌ 2 C a 3 F e 2 S i 3 O 12 + 10 3 M g 3 A l 2 S i 3 O 12 + S i O 2 {\displaystyle 2Ca_{3}Al_{2}Si_{3}O_{12}+{\frac {4}{3}}Fe_{3}Al_{2}Si_{3}O_{12}+2.5Mg_{4}Si_{4}O_{12}+O_{2}\rightleftharpoons 2Ca_{3}Fe_{2}Si_{3}O_{12}+{\frac {10}{3}}Mg_{3}Al_{2}Si_{3}O_{12}+SiO_{2}}
A recent study [ 12 ] showed that the oxygen fugacity of transition referred from Garnet-Garnet reaction is -0.26 l o g f O 2 {\displaystyle logfO_{2}} to +3 l o g f O 2 {\displaystyle logfO_{2}} relative to the Fe-FeO (IW, iron - wütstite ) oxygen buffer .
Disproportionation of ferrous iron at lower mantle conditions also affect the mantle oxidation state. This reaction is different from the reactions mentioned above as it does not incorporate the participation of free oxygen.
3 F e 2 + ( F p ) ⇌ F e + 2 F e 3 + ( B d g ) {\displaystyle 3Fe^{2+}(Fp)\rightleftharpoons Fe+2Fe^{3+}(Bdg)} , [ 5 ] [ 13 ]
FeO resides in the form of ferropericlase ( Fp ) and Fe 2 O 3 resides in the form of bridgmanite ( Bdg ). There is no oxygen fugacity change associated with the reaction. However, as the reaction products differ in density significantly, the metallic iron phase could descend downwards to the Earth's core and get separated from the mantle. In this case, the mantle loses metallic iron and becomes more oxidized.
The equilibrium reaction involving diamond is
M g 2 S i 2 O 6 + 2 M g C O 3 ⇌ 2 M g 2 S i O 4 + 2 C ( D i a m o n d ) + 2 O 2 {\displaystyle Mg_{2}Si_{2}O_{6}+2MgCO_{3}\rightleftharpoons 2Mg_{2}SiO_{4}+2C(Diamond)+2O_{2}} .
Examining the oxygen fugacity of the upper mantle and transition enables us to compare it with the conditions ( equilibrium reaction shown above) required for diamond formation. The results show that the l o g f O 2 {\displaystyle logfO_{2}} is usually 2 units lower than the carbonate-carbon reaction [ 12 ] which means favoring the formation of diamond at transition zone conditions.
It has also been reported that pH decrease would also facilitate the formation of diamond in Mantle conditions. [ 14 ]
H C O O − + H + + H 2 , a q ⇌ C d i a m o n d + 2 H 2 O {\displaystyle HCOO^{-}+H^{+}+H_{2,aq}\rightleftharpoons C_{diamond}+2H_{2}O}
C H 3 C H 2 C O O − + H + ⇌ 3 C d i a m o n d + H 2 , a q + 2 H 2 O {\displaystyle CH_{3}CH_{2}COO^{-}+H^{+}\rightleftharpoons 3C_{diamond}+H_{2,aq}+2H_{2}O}
where the subscript aq means 'aqueous', implying H 2 is dissolved in the solution.
Deep diamonds have become important windows to look into the mineralogy of the Earth's interior . Minerals not stable at the surface could possibly be found within inclusions of superdeep diamonds [ 15 ] —implying they were stable where these diamond crystallized. Because of the hardness of diamonds, the high pressure environment is retained even after transporting to the surface. So far, these superdeep minerals brought by diamonds include ringwoodite , [ 16 ] ice-VII , [ 17 ] cubic δ- N 2 [ 18 ] and Ca- perovskite . [ 19 ] | https://en.wikipedia.org/wiki/Mantle_oxidation_state |
The mantou kiln ( Chinese : 饅頭窯 ; pinyin : mántóu yáo ; Wade–Giles : man-t'ou yao ) or horseshoe-shaped kiln was the most common type of pottery kiln in north China, in historical periods when the dragon kiln dominated south China; both seem to have emerged in the Warring States period of approximately 475 to 221 BC. [ 1 ] It is named (in both English and Chinese) after the Chinese mantou bun or roll, whose shape it (very approximately) resembles; the ground plan resembles a horseshoe . [ 2 ] The kilns are roughly round, with a low dome covering the central firing area, and are generally only 2 to 3 metres across inside. However it is capable of reaching very high temperatures, up to about 1370°C. There is a door or bricked-up opening at the front for loading and unloading, and one or two short chimneys at the rear. [ 2 ]
They are one type of "cross-draught" kilns, where the flames travel more or less horizontally, rather than up from or down to the floor. [ 3 ] The kilns were normally made of brick; sometimes most of the structure was dug out below the loess soil, with only the dome and chimney protruding above ground. In either case the interior was normally lined with a refractory fireclay . In some cases, especially in later periods, the fire box was approached by a tunnel. Initially the kilns were fired with wood, but during the Northern Song period (960–1127) there was a general switch to coal , easily found in north China, which required a smaller fire box, but the introduction of saggars to protect the pieces from gritty coal ash . This changed the reducing quality of the atmosphere during firing, which affected the colours of various wares, [ 1 ] wood giving a reducing atmosphere and coal an oxidizing one. [ 4 ] A firing might take as long as two weeks, including the cooling time. [ 5 ]
The details of the design could be very variable. A temporary "bag wall" might be built at the front of the kiln, once loaded, to protect the wares from the direct flames, and enclose the fire. The back interior wall might be straight, giving a semi-circular shape to the chamber. Various different arrangements for controlling the airflow at front and back by vents and stone doors are found. [ 6 ] Generally the firing was even across the various parts of the chamber compared to the dragon kiln, but the load far smaller, with saggars perhaps only hundreds of pieces, rather than the tens of thousands a large dragon kiln could take for a single firing. [ 7 ]
Wares fired in mantou kilns include Ding ware , Yaozhou ware and other Northern Celadons, Jun , Ru , and Cizhou wares . [ 1 ] The zhenyao "egg-shaped kiln", developed for Jingdezhen ware in the late Ming dynasty , [ 8 ] is in some ways a compromise between mantou and dragon kilns, like a stretched mantou kiln. Official Guan ware had been made at Jingdezhen in a northern-style mantou kiln, rare this far south. [ 9 ] | https://en.wikipedia.org/wiki/Mantou_kiln |
The Mantoux test or Mendel–Mantoux test (also known as the Mantoux screening test , tuberculin sensitivity test , Pirquet test , or PPD test for purified protein derivative) is a tool for screening for tuberculosis (TB) and for tuberculosis diagnosis . It is one of the major tuberculin skin tests used around the world, largely replacing multiple-puncture tests such as the tine test . The Heaf test , a form of tine test, was used until 2005 in the UK, when it was replaced by the Mantoux test. The Mantoux test is endorsed by the American Thoracic Society and Centers for Disease Control and Prevention . It was also used in the USSR and is now prevalent in most of the post-Soviet states , although Soviet mantoux produced many false positives due to children's allergic reaction. [ 1 ]
Tuberculin is a glycerol extract of the tubercle bacillus . Purified protein derivative (PPD) tuberculin is a precipitate of species-nonspecific molecules obtained from filtrates of sterilized, concentrated cultures. The tuberculin reaction was first described by Robert Koch in 1890. The test was first developed and described by the German physician Felix Mendel in 1908. [ 2 ] It is named after Charles Mantoux , a French physician who built on the work of Koch and Clemens von Pirquet to create his test in 1907. However, the test was unreliable due to impurities in tuberculin which tended to cause false results. [ 3 ]
Esmond R. Long and Florence B. Seibert identified the active agent in tuberculin as a protein. Seibert then spent a number of years developing methods for separating and purifying the protein from Mycobacterium tuberculosis , obtaining purified protein derivative (PPD) and enabling the creation of a reliable test for tuberculosis. [ 3 ] Her first publication on the purification of tuberculin appeared in 1934. [ 4 ] By the 1940s, Seibert's PPD was the international standard for tuberculin tests. [ 5 ] In 1939, Russian M.A. Linnikova created a modified version of PPD. In 1954, the Soviet Union started mass production of PPD-L, named after Linnikova. [ 6 ] [ 7 ]
In the Mantoux test, a standard dose of 5 tuberculin units (TU – 0.1 ml), according to the CDC , [ 8 ] or 2 TU of Statens Serum Institute (SSI) tuberculin RT23 in 0.1 ml solution, according to the National Health Service , [ 9 ] is injected intradermally (between the layers of dermis) on the flexor surface of the left forearm, mid-way between elbow and wrist. The injection should be made with a tuberculin syringe, with the needle bevel facing upward. When placed correctly, injection should produce a pale wheal of the skin, 6 to 10 mm in diameter. The result of the test is read after 48–96 hours, ideally after 72 hours/3rd day. This procedure is termed the 'Mantoux technique'. A person who has been exposed to the bacteria would be expected to mount an immune response in the area of skin containing the bacterial proteins. This response is a classic example of 'delayed-type hypersensitivity reaction' ( DTH ), a type IV of hypersensitivities . T cells and myeloid cells are attracted to the site of reaction in 1–3 days and generate local inflammation . The reaction is read by measuring the diameter of induration (palpable raised, hardened area) across the forearm (perpendicular to the long axis) in millimeters. If there is no induration, the result should be recorded as "0 mm". Erythema (redness) should not be measured. [ 10 ] In the Pirquet version of the test tuberculin is applied to the skin via scarification . [ 11 ]
The results of this test must be interpreted carefully. The person's medical risk factors determine at which increment (5 mm, 10 mm, or 15 mm) of induration the result is considered positive. [ 12 ] A positive result indicates TB exposure.
A tuberculin test conversion is defined as an increase of 10 mm or more within a two-year period, regardless of age. Alternative criteria include increases of 6, 12, 15 or 18 mm. [ 14 ]
TST (tuberculin skin test) positive is measured by size of induration. The size of the induration considered to be a positive result depends on risk factors. For example, a low-risk patient must have a larger induration for a positive result than a high-risk patient. High-risk groups include recent contacts, those with HIV, those with chest radiograph with fibrotic changes, organ transplant recipients, and those with immunosuppression. [ citation needed ]
A meta-analysis in 2014 found that the Bacillus Calmette–Guérin (BCG) vaccine reduced infections by 19–27% and reduced progression to active tuberculosis by 71%. [ 15 ] The Ohio Department of Health states that it give 80% of children protection against tuberculous meningitis and miliary tuberculosis . Therefore, a positive TST/PPD in a person who has received BCG vaccine is interpreted as latent TB infection (LTBI). [ 16 ] Due to the test's low specificity, most positive reactions in low-risk individuals are false positives. [ 17 ] A false positive result may be caused by nontuberculous mycobacteria or previous administration of BCG vaccine. Vaccination with BCG may result in a false-positive result for many years after vaccination. [ 18 ]
False positives can also occur when the injected area is touched, causing swelling and itching. If the swelling is less than 5 mm, it is possibly due to error by the healthcare personnel causing inflammation to the area. [ citation needed ]
Another source of false positive results can be allergic reaction or hypersensitivity . Although rare (about 0.08 reported reactions per million doses of tuberculin), these reactions can be dangerous and precautions should be taken by having epinephrin available. [ 19 ]
Reaction to the PPD or tuberculin test is suppressed by the following conditions:
This is because the immune system needs to be functional to mount a response to the protein derivative injected under the skin. A false negative result may occur in a person who has been recently infected with TB, but whose immune system hasn't yet reacted to the bacteria.
In case a second tuberculin test is necessary it should be carried out in the other arm to avoid hypersensitising the skin.
The role of Mantoux testing in people who have been vaccinated is disputed. The US recommends that tuberculin skin testing is not contraindicated for BCG-vaccinated persons, and prior BCG vaccination should not influence the interpretation of the test. The UK recommends that interferon-γ testing should be used to help interpret positive Mantoux tests of over 5 mm, [ 20 ] and repeated tuberculin skin testing must not be done in people who have had BCG vaccinations. In general, the US recommendation may result in a larger number of people being falsely diagnosed with latent tuberculosis, while the UK approach has an increased chance of missing patients with latent tuberculosis who should be treated. [ citation needed ]
According to the US guidelines, latent tuberculosis infection diagnosis and treatment is considered for any BCG-vaccinated person whose skin test is 10 mm or greater, if any of these circumstances are present: [ citation needed ]
In cases of anergy , a lack of reaction by the body's defence mechanisms when it comes into contact with foreign substances, the tuberculin reaction will occur weakly, thus compromising the value of Mantoux testing. For example, anergy is present in AIDS , a disease which strongly depresses the immune system. Therefore, anergy testing is advised in cases where there is suspicion that anergy is present. However, routine anergy skin testing is not recommended. [ 21 ]
Some people who have been infected with TB may have a negative reaction when tested years after infection, as the immune system response may gradually wane. This initial skin test, though negative, may stimulate (boost) the body's ability to react to tuberculin in future tests. Thus, a positive reaction to a subsequent test may be misinterpreted as a new infection, when in fact it is the result of the boosted reaction to an old infection. [ 22 ]
Use of two-step testing is recommended for initial skin testing of adults who will be retested periodically (e.g., health care workers). This ensures any future positive tests can be interpreted as being caused by a new infection, rather than simply a reaction to an old infection. [ citation needed ]
A person who is diagnosed as "infected in the distant past" on two-step testing is called a "tuberculin reactor". [ citation needed ]
The US recommendation that prior BCG vaccination be ignored results in almost universal false diagnosis of tuberculosis infection in people who have had BCG (mostly foreign nationals). [ citation needed ]
According to the guidelines published by Centers for Disease Control and Prevention in 2005, the results are re-categorized into 3 parts based on their previous or baseline outcomes: [ citation needed ]
In addition to tuberculin skin tests such as (principally) the Mantoux test, interferon gamma release assays (IGRAs) have become common in clinical use in the 2010s. In some contexts they are used instead of TSTs, whereas in other contexts TSTs and IGRAs both continue to be useful. [ 25 ]
The QuantiFERON-TB Gold blood test measures the patient's immune reactivity to the TB bacterium, and is useful for initial and serial testing of persons with an increased risk of latent or active tuberculosis infection. Guidelines for its use were released by the CDC in December 2005. [ 26 ] QuantiFERON-TB Gold is FDA -approved in the United States , has CE Mark approval in Europe and has been approved by the MHLW in Japan . The interferon gamma release assay is the preferred method for patients who have had immunosuppression and are about to start biological therapies. [ 27 ]
T-SPOT.TB is another IGRA; it uses the ELISPOT method. [ citation needed ]
The Heaf tuberculin skin test was used in the United Kingdom, but discontinued in 2005. The equivalent Mantoux test positive levels done with 10 TU (0.1 ml at 100 TU/ml, 1:1000) are [ citation needed ] | https://en.wikipedia.org/wiki/Mantoux_test |
An underground personnel carrier is any heavy duty vehicle designed specifically for the safe transport of personnel and their supplies into underground work areas. The most common underground applications is for the mining of either precious metal or coal .
Where tight turning in confined spaces is necessary, personnel carriers designed on tractors are common. Heavy duty fenders, bumpers and man baskets (gondolas) are fabricated to mount on the tractor or tractor frames to provide more durability.
These personnel carriers use a front loader to perform various loader applications. Also a front basket is typically attached to the front loader arms so that they may be lifted. These carriers are typically built to carry 5 or 7 men.
Some personnel carriers use a heavy duty hydraulic rear hitch that can two various attachments. Towing PCs can be used in conjunction with a front loader as well.
Other narrow vein personnel carriers are designed for a specific job based on their attachments. These attachments include rear and/or front lift baskets for utility and electrical work, mechanic packages, cable reels, heavy duty canes, ANFO loaders, and shotcrete booms.
These personnel carriers are designed and built from the ground up. They are typically 5 man to 15 man carriers. These carriers may also be designed using multiple attachments for job specific applications.
In the coal mining industry low profile personnel carriers are the most commonly used. These carriers may only have a 3 to 3.5 feet (0.91 to 1.07 m) height dimension and carry up to 14 men, and are typically built from the ground up and can be designed with job specific attachments.
A mantrip is a shuttle for transporting miners down into an underground mine at the start of their shift, and out again at the end. Mantrips usually take the form of a train , running on a mine railway and operating like a cable car . Mantrips may also be self-powered, for example by a diesel locomotive . Other types of mantrips do not require a track and take the form of a pickup truck running on rubber tires. Because many mines have low ceilings, mantrips tend to have a reduced height.
In the United States, the Mine Safety and Health Administration has published safety regulations governing the operation of mantrips. [ 1 ] | https://en.wikipedia.org/wiki/Mantrip |
A manual override (MO) or manual analog override (MAO) is a mechanism where control is taken from an automated system and given to the user. For example, a manual override in photography refers to the ability for the human photographer to turn off the automatic aperture sizing, automatic focusing , or any other automated system on the camera. [ 1 ]
Some manual overrides can be used to veto an automated system's judgment when the system is in error. An example of this is a printer's ink level detection: in one case, a researcher found that when he overrode the system, up to 38% more pages could be printed at good quality by the printer than the automated system would have allowed. [ 2 ]
Automated systems are becoming increasingly common and integrated into everyday objects such as automobiles and domestic appliances . This development of ubiquitous computing raises general issues of policy and law about the need for manual overrides for matters of great importance such as life-threatening situations and major economic decisions. The loyalty of such autonomous devices then becomes an issue. If they follow rules installed by the manufacturer or required by law and refuse to cede control in some situations then the owners of the devices may feel disempowered, alienated and lacking true ownership. [ 3 ]
China Airlines Flight 140 crashed, causing many deaths, due to a misunderstanding about the manual overrides for the autopilot . The Take-Off/Go Around system had been activated to abort a landing. It was programmed to ignore manual controls in this situation but the human pilots tried to continue the landing. The conflicting control signals from the pilots and autopilot then resulted in the aircraft stalling and crashing. The autopilot for this aircraft type was then reprogrammed so that it would never ignore a manual override. [ 4 ] | https://en.wikipedia.org/wiki/Manual_override |
Manuel Ballester Boix (born in Barcelona on 27 June 1919; died 5 April 2005) was a Spanish chemist.
He received his degree at the University of Barcelona in 1944, his doctorate in Madrid, and finished his training at Harvard University in 1951. [ 1 ] In 1944 he formed a team at the Spanish National Research Council . His work has largely been in kinetics and organic chemistry . [ 2 ]
This article about a Spanish scientist is a stub . You can help Wikipedia by expanding it .
This biographical article about a chemist is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Manuel_Ballester |
Manuel Bibes , born on July 15, 1976, in Sainte-Foy-la-Grande , is a French physicist specializing in functional oxides, [ 1 ] multiferroic materials, and spintronics . He is currently a Research Director at the National Center for Scientific Research (CNRS) .
After earning an engineering degree from the Institut National des Sciences Appliquées de Toulouse in 1998, Bibes completed his Ph.D. under the supervision of Josep Fontcuberta at the ICMAB , at the Autonomous University of Barcelona in 2001, focusing on thin manganite films and their application in spintronics . [ 2 ] His PhD was followed by a postdoctoral fellowship at the Joint Physics Unit CNRS/Thales (currently known as Laboratory Albert Fert ) under the guidance of Prof. Albert Fert . Bibes joined the CNRS in 2003 at the Institute of Fundamental Electronics, now known as the Center for Nanoscience and Nanotechnology (C2N). Afterwards he completed research stays at MIT and the University of Cambridge as a visiting researcher and joined the Laboratory Albert Fert at 2007. [ 3 ] All his research publications are listed in Google Scholar. [ 4 ]
Throughout his career, Bibes has been a leader in research of multiferroic materials [ 5 ] (which simultaneously exhibits magnetic and ferroelectric properties) and their utilisation in electrical control of magnetism. In 2009, his team discovered the phenomenon of giant tunnel electroresistance in ferroelectric tunnel junctions [ 6 ] (results published in Nature [ 7 ] ) demonstrating their potential as artificial synapses . [ 8 ] In 2016, in collaboration with the Spintec [ 9 ] laboratory, he demonstrated that non-magnetic oxide interfaces can be used as ultrasensitive spin detectors. This findings led to a collaboration with Intel [ 10 ] for the development of a new type of energy efficient transistor [ 11 ] ( MESO ) aimed at replacing the current transistors based on CMOS technology. Since 2018, Manuel Bibes has been recognized as a Highly Cited Researcher by Clarivate Analytics . [ 12 ] In June 2022, along with Agnès Barthélémy, Ramamoorthy Ramesh and Nicola Spaldin , he received the Europhysics Prize from the European Physical Society for their significant contributions to the fundamental and applied physics of multiferroic and magnetoelectric materials. [ 13 ] In October 2024, he co-founds the start-up company Nellow , together with Laurent Vila and Jean-Philippe Attané from Spintec. Nellow aims to develop and commercialize chips with an ultralow power consumption for logic and artificial intelligence . | https://en.wikipedia.org/wiki/Manuel_Bibes |
Manufacture Modules Technologies Sarl (MMT) is a Swiss company established in Geneva in 2015 which originally specialised in the development and commercialization of "Horological Smartwatch modules", firmware, apps and cloud. Located at Geneva's Skylab high-tech hub, it expanded into the development and manufacturing of "E-Straps" operated with a mobile application. [ 1 ]
Philippe Fraboulet is the CEO. [ 2 ]
In June 2015, Fullpower Technologies and Union Horlogère Suisse (Swiss Watchmakers Corporation) formed MMT as a joint venture, which then launched the MotionX Horological Smartwatch Open Platform for the Swiss watch industry. [ 3 ] The initial licensees were Frederique Constant , Alpina and Mondaine , brands owned by Union Horlogère Suisse. [ 4 ] Fullpower created and managed the circuit design, firmware, smartphone applications (including sleep activity), as well as the cloud Infrastructure. MMT managed the Swiss watch movement development and production as well as licensing and support. [ 5 ] [ 6 ]
In July 2016, Union Horlogere Holding and MMT were spun-out of the Frédérique Constant Group. [ 7 ]
Fullpower Technologies' 19.99% share was acquired by Union Horlogere Holding BV, giving it 100% of MMT's shares. [ 8 ]
The company offers firmware, a cloud, manufacturing, service and over-the-air facilities for upgrades. The company also offers its own apps, which bear the label “Swiss Made software”. [ 9 ] | https://en.wikipedia.org/wiki/Manufacture_Modules_Technologies |
The Manufacturing Engineering Centre ( MEC ) is an international R&D Centre of Excellence for Advanced Manufacturing and Information Technology. The MEC was founded in 1996 under the directorship of Professor Duc Truong Pham. [ 1 ] The Centre forms part of Cardiff University , which dates back to 1883 and is one of Britain's major civic universities.
The MEC's purpose is to conduct research and development in all major areas of Advanced Manufacturing and use the output to promote the introduction of new manufacturing technology and practice to industry. It was the first autonomous research centre created by Cardiff University. [ 2 ]
The MEC conducts basic, strategic and applied research as well as technology transfer with partners from 22 countries in Europe, Asia and the Americas. The research spans a broad spectrum of subjects, including robotics and microsystems, sensor systems, high-speed automation and intelligent control , rapid manufacturing , micromanufacturing, nanotechnology , quality engineering, multimedia , virtual reality and enterprise information management.
Since 1996, the Centre has received over £50 million in grants and contracts and has attracted hundreds of industrial partners. In 2004, the MEC won two EC 6th Framework Networks of Excellence contracts totalling 15M Euros in value. The two Networks of Excellence led by the MEC, I*PROMS and 4M, involve some 50 centres of excellence in the field of Advanced Manufacturing across the EU.
As a Centre of Excellence for Technology and Industrial Collaboration (CETIC) sponsored by the Welsh Assembly Government (WAG) and the European Regional Development Fund (ERDF), the MEC has contributed significantly to the Welsh economy, having completed thousands of projects with local companies and helped to generate and safeguard jobs in the region. [ 3 ]
Under Professor Pham's leadership, the MEC was awarded the DTI University/Industry First Prize by the Secretary of State for Trade and Industry for its success in building research partnerships with industry (March 1999), and the Queen's Anniversary Prize for Higher and Further Education in recognition of its contribution made to the economy (February 2001). [ 3 ] | https://en.wikipedia.org/wiki/Manufacturing_Engineering_Centre |
Manufacturing engineering or production engineering is a branch of professional engineering that shares many common concepts and ideas with other fields of engineering such as mechanical, chemical, electrical, and industrial engineering.
Manufacturing engineering requires the ability to plan the practices of manufacturing; to research and to develop tools, processes, machines, and equipment; and to integrate the facilities and systems for producing quality products with the optimum expenditure of capital. [ 1 ]
The manufacturing or production engineer's primary focus is to turn raw material into an updated or new product in the most effective, efficient & economic way possible. An example would be a company uses computer integrated technology in order for them to produce their product so that it is faster and uses less human labor.
Manufacturing Engineering is based on core industrial engineering and mechanical engineering skills, adding important elements from mechatronics, commerce, economics, and business management.
This field also deals with the integration of different facilities and systems for producing quality products (with optimal expenditure) by applying the principles of physics and the results of manufacturing systems studies, such as the following:
Manufacturing engineers develop and create physical artifacts, production processes, and technology. It is a very broad area which includes the design and development of products. Manufacturing engineering is considered to be a subdiscipline of industrial engineering / systems engineering and has very strong overlaps with mechanical engineering . Manufacturing engineers' success or failure directly impacts the advancement of technology and the spread of innovation. This field of manufacturing engineering emerged from the tool and die discipline in the early 20th century. It expanded greatly from the 1960s when industrialized countries introduced factories with:
1. Numerical control machine tools and automated systems of production.
2. Advanced statistical methods of quality control : These factories were pioneered by the American electrical engineer William Edwards Deming , who was initially ignored by his home country. The same methods of quality control later turned Japanese factories into world leaders in cost-effectiveness and production quality.
3. Industrial robots on the factory floor, introduced in the late 1970s: These computer-controlled welding arms and grippers could perform simple tasks such as attaching a car door quickly and flawlessly 24 hours a day. This cut costs and improved production speed.
The history of manufacturing engineering can be traced to factories in the mid-19th century USA and 18th century UK. Although large home production sites and workshops were established in China, ancient Rome, and the Middle East, the Venice Arsenal provides one of the first examples of a factory in the modern sense of the word. Founded in 1104 in the Republic of Venice several hundred years before the Industrial Revolution , this factory mass-produced ships on assembly lines using manufactured parts. The Venice Arsenal apparently produced nearly one ship every day and, at its height, employed 16,000 people.
Many historians regard Matthew Boulton's Soho Manufactory (established in 1761 in Birmingham) as the first modern factory. Similar claims can be made for John Lombe's silk mill in Derby (1721), or Richard Arkwright's Cromford Mill (1771). The Cromford Mill was purpose-built to accommodate the equipment it held and to take the material through the various manufacturing processes.
One historian, Jack Weatherford , contends that the first factory was in Potosí . The Potosi factory took advantage of the abundant silver that was mined nearby and processed silver ingot slugs into coins.
British colonies in the 19th century built factories simply as buildings where a large number of workers gathered to perform hand labor, usually in textile production. This proved more efficient for the administration and distribution of materials to individual workers than earlier methods of manufacturing, such as cottage industries or the putting-out system.
Cotton mills used inventions such as the steam engine and the power loom to pioneer the industrial factories of the 19th century, where precision machine tools and replaceable parts allowed greater efficiency and less waste. This experience formed the basis for the later studies of manufacturing engineering. Between 1820 and 1850, non-mechanized factories supplanted traditional artisan shops as the predominant form of manufacturing institution.
Henry Ford further revolutionized the factory concept and thus manufacturing engineering in the early 20th century with the innovation of mass production. Highly specialized workers situated alongside a series of rolling ramps would build up a product such as (in Ford's case) an automobile. This concept dramatically decreased production costs for virtually all manufactured goods and brought about the age of consumerism.
Modern manufacturing engineering studies include all intermediate processes required for the production and integration of a product's components.
Some industries, such as semiconductor and steel manufacturers use the term "fabrication" for these processes.
Automation is used in different processes of manufacturing such as machining and welding. Automated manufacturing refers to the application of automation to produce goods in a factory. The main advantages of automated manufacturing for the manufacturing process are realized with effective implementation of automation and include higher consistency and quality, reduction of lead times, simplification of production, reduced handling, improved workflow, and improved worker morale.
Robotics is the application of mechatronics and automation to create robots, which are often used in manufacturing to perform tasks that are dangerous, unpleasant, or repetitive. These robots may be of any shape and size, but all are preprogrammed and interact physically with the world. To create a robot, an engineer typically employs kinematics (to determine the robot's range of motion) and mechanics (to determine the stresses within the robot). Robots are used extensively in manufacturing engineering.
Robots allow businesses to save money on labor, perform tasks that are either too dangerous or too precise for humans to perform economically, and ensure better quality. Many companies employ assembly lines of robots, and some factories are so robotized that they can run by themselves. Outside the factory, robots have been employed in bomb disposal, space exploration, and many other fields. Robots are also sold for various residential applications.
Manufacturing Engineers focus on the design, development, and operation of integrated systems of production to obtain high quality & economically competitive products. [ 2 ] These systems may include material handling equipment, machine tools, robots, or even computers or networks of computers.
Manufacturing engineers possess an associate's or bachelor's degree in engineering with a major in manufacturing engineering. The length of study for such a degree is usually two to five years followed by five more years of professional practice to qualify as a professional engineer. Working as a manufacturing engineering technologist involves a more applications-oriented qualification path.
Academic degrees for manufacturing engineers are usually the Associate or Bachelor of Engineering, [BE] or [BEng], and the Associate or Bachelor of Science, [BS] or [BSc]. For manufacturing technologists the required degrees are Associate or Bachelor of Technology [B.TECH] or Associate or Bachelor of Applied Science [BASc] in Manufacturing, depending upon the university. Master's degrees in engineering manufacturing include Master of Engineering [ME] or [MEng] in Manufacturing, Master of Science [M.Sc] in Manufacturing Management, Master of Science [M.Sc] in Industrial and Production Management, and Master of Science [M.Sc] as well as Master of Engineering [ME] in Design, which is a subdiscipline of manufacturing. Doctoral [PhD] or [DEng] level courses in manufacturing are also available depending on the university.
The undergraduate degree curriculum generally includes courses in physics, mathematics, computer science, project management, and specific topics in mechanical and manufacturing engineering. Initially, such topics cover most, if not all, of the subdisciplines of manufacturing engineering. Students then choose to specialize in one or more subdisciplines towards the end of their degree work.
The Foundational Curriculum for a Bachelor's Degree in Manufacturing Engineering or Production Engineering includes below mentioned syllabus. This syllabus is closely related to Industrial Engineering and Mechanical Engineering, but it differs by placing more emphasis on Manufacturing Science or Production Science. It includes the following areas:
A degree in Manufacturing Engineering typically differs from Mechanical Engineering in only a few specialized classes. Mechanical Engineering degrees focus more on the product design process and on complex products which requires more mathematical expertise.
Certification and licensure:
In some countries, "professional engineer" is the term for registered or licensed engineers who are permitted to offer their professional services directly to the public. Professional Engineer , abbreviated (PE - USA) or (PEng - Canada), is the designation for licensure in North America. To qualify for this license, a candidate needs a bachelor's degree from an ABET -recognized university in the USA, a passing score on a state examination, and four years of work experience usually gained via a structured internship. In the USA, more recent graduates have the option of dividing this licensure process into two segments. The Fundamentals of Engineering (FE) exam is often taken immediately after graduation and the Principles and Practice of Engineering exam is taken after four years of working in a chosen engineering field.
Society of Manufacturing Engineers (SME) certification (USA):
The SME administers qualifications specifically for the manufacturing industry. These are not degree level qualifications and are not recognized at the professional engineering level. The following discussion deals with qualifications in the USA only. Qualified candidates for the Certified Manufacturing Technologist Certificate (CMfgT) must pass a three-hour, 130-question multiple-choice exam. The exam covers math, manufacturing processes, manufacturing management, automation, and related subjects. Additionally, a candidate must have at least four years of combined education and manufacturing-related work experience.
Certified Manufacturing Engineer (CMfgE) is an engineering qualification administered by the Society of Manufacturing Engineers, Dearborn, Michigan, USA. Candidates qualifying for a Certified Manufacturing Engineer credential must pass a four-hour, 180-question multiple-choice exam which covers more in-depth topics than the CMfgT exam. CMfgE candidates must also have eight years of combined education and manufacturing-related work experience, with a minimum of four years of work experience.
Certified Engineering Manager (CEM). The Certified Engineering Manager Certificate is also designed for engineers with eight years of combined education and manufacturing experience. The test is four hours long and has 160 multiple-choice questions. The CEM certification exam covers business processes, teamwork, responsibility, and other management-related categories.
Many manufacturing companies, especially those in industrialized nations, have begun to incorporate computer-aided engineering (CAE) programs into their existing design and analysis processes, including 2D and 3D solid modeling computer-aided design (CAD). This method has many benefits, including easier and more exhaustive visualization of products, the ability to create virtual assemblies of parts, and ease of use in designing mating interfaces and tolerances.
Other CAE programs commonly used by product manufacturers include product life cycle management (PLM) tools and analysis tools used to perform complex simulations. Analysis tools may be used to predict product response to expected loads, including fatigue life and manufacturability. These tools include finite element analysis (FEA), computational fluid dynamics (CFD), and computer-aided manufacturing (CAM).
Using CAE programs, a mechanical design team can quickly and cheaply iterate the design process to develop a product that better meets cost, performance, and other constraints. No physical prototype need be created until the design nears completion, allowing hundreds or thousands of designs to be evaluated, instead of relatively few. In addition, CAE analysis programs can model complicated physical phenomena which cannot be solved by hand, such as viscoelasticity , complex contact between mating parts, or non-Newtonian flows.
Just as manufacturing engineering is linked with other disciplines, such as mechatronics, multidisciplinary design optimization (MDO) is also being used with other CAE programs to automate and improve the iterative design process. MDO tools wrap around existing CAE processes, allowing product evaluation to continue even after the analyst goes home for the day. They also utilize sophisticated optimization algorithms to more intelligently explore possible designs, often finding better, innovative solutions to difficult multidisciplinary design problems.
On the business side of manufacturing engineering, enterprise resource planning (ERP) tools can overlap with PLM tools and use connector programs with CAD tools to share drawings, sync revisions, and be the master for certain data used in the other modern tools above, like part numbers and descriptions.
Manufacturing engineering is an extremely important discipline worldwide. It goes by different names in different countries. In the United States and the continental European Union it is commonly known as Industrial Engineering and in the United Kingdom and Australia it is called Manufacturing Engineering. [ 3 ]
Mechanics, in the most general sense, is the study of forces and their effects on matter. Typically, engineering mechanics is used to analyze and predict the acceleration and deformation (both elastic and plastic) of objects under known forces (also called loads) or stresses. Subdisciplines of mechanics include:
If the engineering project were to design a vehicle, statics might be employed to design the frame of the vehicle to evaluate where the stresses will be most intense. Dynamics might be used when designing the car's engine to evaluate the forces in the pistons and cams as the engine cycles. Mechanics of materials might be used to choose appropriate materials for the manufacture of the frame and engine. Fluid mechanics might be used to design a ventilation system for the vehicle or to design the intake system for the engine.
Kinematics is the study of the motion of bodies (objects) and systems (groups of objects), while ignoring the forces that cause the motion. The movement of a crane and the oscillations of a piston in an engine are both simple kinematic systems. The crane is a type of open kinematic chain, while the piston is part of a closed four-bar linkage. Engineers typically use kinematics in the design and analysis of mechanisms. Kinematics can be used to find the possible range of motion for a given mechanism, or, working in reverse, can be used to design a mechanism that has a desired range of motion.
Drafting or technical drawing is the means by which manufacturers create instructions for manufacturing parts. A technical drawing can be a computer model or hand-drawn schematic showing all the dimensions necessary to manufacture a part, as well as assembly notes, a list of required materials, and other pertinent information. A U.S engineer or skilled worker who creates technical drawings may be referred to as a drafter or draftsman . Drafting has historically been a two-dimensional process, but computer-aided design (CAD) programs now allow the designer to create in three dimensions.
Instructions for manufacturing a part must be fed to the necessary machinery, either manually, through programmed instructions, or through the use of a computer-aided manufacturing (CAM) or combined CAD/CAM program. Optionally, an engineer may also manually manufacture a part using the technical drawings, but this is becoming an increasing rarity with the advent of computer numerically controlled (CNC) manufacturing. Engineers primarily manufacture parts manually in the areas of applied spray coatings, finishes, and other processes that cannot economically or practically be done by a machine.
Drafting is used in nearly every subdiscipline of mechanical and manufacturing engineering, and by many other branches of engineering and architecture. Three-dimensional models created using CAD software are also commonly used in finite element analysis (FEA) and computational fluid dynamics (CFD).
Machine tools employ some sort of tool that does the cutting or shaping. All machine tools have some means of constraining the workpiece and providing a guided movement of the parts of the machine. Metal fabrication is the building of metal structures by cutting, bending, and assembling processes.
Computer-integrated manufacturing (CIM) is the manufacturing approach of using computers to control the entire production process. Computer-integrated manufacturing is used in automotive, aviation, space, and ship building industries.
Mechatronics is an engineering discipline that deals with the convergence of electrical, mechanical and manufacturing systems. Such combined systems are known as electromechanical systems and are widespread. Examples include automated manufacturing systems, heating, ventilation and air-conditioning systems, and various aircraft and automobile subsystems.
The term mechatronics is typically used to refer to macroscopic systems, but futurists have predicted the emergence of very small electromechanical devices. Already such small devices, known as Microelectromechanical systems (MEMS), are used in automobiles to initiate the deployment of airbags, in digital projectors to create sharper images, and in inkjet printers to create nozzles for high-definition printing. In the future, it is hoped that such devices will be used in tiny implantable medical devices and to improve optical communication.
Textile engineering courses deal with the application of scientific and engineering principles to the design and control of all aspects of fiber, textile, and apparel processes, products, and machinery. These include natural and man-made materials, interaction of materials with machines, safety and health, energy conservation, and waste and pollution control. Additionally, students are given experience in plant design and layout, machine and wet process design and improvement, and designing and creating textile products. Throughout the textile engineering curriculum, students take classes from other engineering and disciplines including: mechanical, chemical, materials and industrial engineering.
Advanced composite materials (engineering) (ACMs) are also known as advanced polymer matrix composites. These are generally characterized or determined by unusually high strength fibres with unusually high stiffness, or modulus of elasticity characteristics, compared to other materials, while bound together by weaker matrices. Advanced composite materials have broad, proven applications, in the aircraft, aerospace, and sports equipment sectors. Even more specifically ACMs are very attractive for aircraft and aerospace structural parts. Manufacturing ACMs is a multibillion-dollar industry worldwide. Composite products range from skateboards to components of the space shuttle. The industry can be generally divided into two basic segments, industrial composites and advanced composites.
Manufacturing engineering is just one facet of the engineering manufacturing industry. Manufacturing engineers enjoy improving the production process from start to finish. They have the ability to keep the whole production process in mind as they focus on a particular portion of the process. Successful students in manufacturing engineering degree programs are inspired by the notion of starting with a natural resource, such as a block of wood, and ending with a usable, valuable product, such as a desk, produced efficiently and economically.
Manufacturing engineers are closely connected with engineering and industrial design efforts. Examples of major companies that employ manufacturing engineers in the United States include General Motors Corporation, Ford Motor Company, Chrysler, Boeing , Gates Corporation and Pfizer. Examples in Europe include Airbus , Daimler, BMW , Fiat, Navistar International , and Michelin Tyre.
Industries where manufacturing engineers are generally employed include:
A flexible manufacturing system (FMS) is a manufacturing system in which there is some amount of flexibility that allows the system to react to changes, whether predicted or unpredicted. This flexibility is generally considered to fall into two categories, both of which have numerous subcategories.
The first category, machine flexibility, covers the system's ability to be changed to produce new product types and the ability to change the order of operations executed on a part. The second category, called routing flexibility, consists of the ability to use multiple machines to perform the same operation on a part, as well as the system's ability to absorb large-scale changes, such as in volume, capacity, or capability.
Most FMS systems comprise three main systems. The work machines, which are often automated CNC machines, are connected by a material handling system to optimize parts flow, and to a central control computer, which controls material movements and machine flow. The main advantages of an FMS is its high flexibility in managing manufacturing resources like time and effort in order to manufacture a new product. The best application of an FMS is found in the production of small sets of products from a mass production.
Computer-integrated manufacturing (CIM) in engineering is a method of manufacturing in which the entire production process is controlled by computer. Traditionally separated process methods are joined through a computer by CIM. This integration allows the processes to exchange information and to initiate actions. Through this integration, manufacturing can be faster and less error-prone, although the main advantage is the ability to create automated manufacturing processes. Typically CIM relies on closed-loop control processes based on real-time input from sensors. It is also known as flexible design and manufacturing.
Friction stir welding was discovered in 1991 by The Welding Institute (TWI). This innovative steady state (non-fusion) welding technique joins previously un-weldable materials, including several aluminum alloys . It may play an important role in the future construction of airplanes, potentially replacing rivets. Current uses of this technology to date include: welding the seams of the aluminum main space shuttle external tank, the Orion Crew Vehicle test article, Boeing Delta II and Delta IV Expendable Launch Vehicles and the SpaceX Falcon 1 rocket; armor plating for amphibious assault ships; and welding the wings and fuselage panels of the new Eclipse 500 aircraft from Eclipse Aviation, among an increasingly growing range of uses.
Other areas of research are Product Design , MEMS (Micro-Electro-Mechanical Systems), Lean Manufacturing , Intelligent Manufacturing Systems, Green Manufacturing, Precision Engineering, Smart Materials, etc. | https://en.wikipedia.org/wiki/Manufacturing_engineering |
Manufacturing execution systems ( MES ) are computerized systems used in manufacturing to track and document the transformation of raw materials to finished goods. MES provides information that helps manufacturing decision-makers understand how current conditions on the plant floor can be optimized to improve production output. [ 1 ] MES works as real-time monitoring system to enable the control of multiple elements of the production process (e.g. inputs, personnel, machines and support services).
MES may operate across multiple function areas, for example management of product definitions across the product life-cycle , resource scheduling , order execution and dispatch, production analysis and downtime management for overall equipment effectiveness (OEE), product quality, or materials track and trace . [ 2 ] MES creates the "as-built" record, capturing the data, processes and outcomes of the manufacturing process. This can be especially important in regulated industries, such as food and beverage or pharmaceutical, where documentation and proof of processes, events and actions may be required.
The idea of MES might be seen as an intermediate step between an enterprise resource planning (ERP) system, and a supervisory control and data acquisition (SCADA) or process control system, although historically, exact boundaries have fluctuated. Industry groups such as Manufacturing Enterprise Solutions Association were created in the early 1990s to address the complexity, and advise on the execution of manufacturing execution systems.
Manufacturing execution systems, known as MES, are software programs created to oversee and enhance production operations. They play a role in boosting efficiency resolving production line issues swiftly and ensuring transparency by collecting and analyzing real time data.
MES effectively manage production resources like materials, labor, equipment and processes. Their features include tracking production, quality management work order handling, inventory control, data analysis and reporting. These capabilities empower businesses to streamline their production processes.
These systems often integrate with ERP systems to align the company's business operations with its production activities. This integration fosters information flow across departments enhancing efficiency and productivity. Organizations like MESA International provide guidance in implementing and advancing MES systems to help companies navigate the intricacies of manufacturing operations. [ 3 ]
"Manufacturing Execution Systems [help] create flawless manufacturing processes and provide real-time feedback of requirement changes", [ 4 ] and provide information at a single source. [ 5 ] Other benefits from a successful MES implementation might include:
A wide variety of systems arose using collected data for a dedicated purpose. Further development of these systems during the 1990s introduced overlap in functionality. Then the Manufacturing Enterprise Solutions Association International (MESA) introduced some structure by defining 11 functions that set the scope of MES. In 2000, the ANSI/ISA-95 standard merged this model with the Purdue Reference Model (PRM). [ 7 ]
A functional hierarchy was defined in which MES were situated at Level 3 between ERP at Level 4 and process control at Levels 0, 1, 2. With the publication of the third part of the standard in 2005, activities in Level 3 were divided over four main operations: production, quality, logistics and maintenance.
Between 2005 and 2013, additional or revised parts of the ANSI/ISA-95 standard defined the architecture of an MES into more detail, covering how to internally distribute functionality and what information to exchange internally as well as externally. [ citation needed ]
Over the years, international standards and models have refined the scope of such systems in terms of activities [ citation needed ] . These typically include:
MES integrates with ISA-95 (previous Purdue Reference Model, “95” ) with multiple relationships.
The collection of systems acting on the ISA-95 Level 3 can be called manufacturing operations management systems (MOMS). Apart from an MES, there are typically laboratory information management system (LIMS), warehouse management system (WMS) and computerized maintenance management system (CMMS). From the MES point of view, possible information flows are:
Examples of systems acting on ISA-95 Level 4 are product lifecycle management (PLM), enterprise resource planning (ERP), customer relationship management (CRM), human resource management (HRM), and process development execution system (PDES). From the MES point of view, possible information flows are:
In many cases, middleware enterprise application integration (EAI) systems are being used to exchange transaction messages between MES and Level 4 systems. A common data definition, B2MML, has been defined within the ISA-95 standard to link MES systems to these Level 4 systems.
Systems acting on ISA-95 Level 2 are supervisory control and data acquisition (SCADA), programmable logic controllers (PLC), distributed control systems (DCS) and building automation systems (BAS). Information flows between MES and these process control systems are roughly similar:
Most MES systems include connectivity as part of their product offering. Direct communication of plant floor equipment data is established by connecting to the PLC. Often, plant floor data is first collected and diagnosed for real-time control in a DCS or SCADA system. In this case, the MES systems connect to these Level 2 systems for exchanging plant floor data.
Until recently, the industry standard for plant floor connectivity has been OLE for Process Control (OPC), but it is now moving to OPC Unified Architecture (OPC-UA); meaning that OPC-UA compatible systems will not necessarily run only on Microsoft Windows environment, but can also run on Linux or other embedded systems, decreasing the cost of SCADA systems, and rendering them more open, with robust security. | https://en.wikipedia.org/wiki/Manufacturing_execution_system |
A manufacturing supermarket (or market location) is, for a factory process, what a retail supermarket is for the customer. The customers draw products from the 'shelves' as needed and this can be detected by the supplier who then initiates a replenishment of that item. It was the observation that this 'way of working' could be transferred from retail to manufacturing which is one of the cornerstones of the Toyota Production System (TPS).
In the 1950s Toyota sent teams to the United States to learn how they achieved mass-production. However, the Toyota Delegation first got inspiration for their production system at an American Supermarket (a Piggly Wiggly, to be precise). They saw the virtue in the supermarket only reordering and restocking goods once they’d been bought by customers.
In a supermarket (like the TPS) customers (processes) buy what they need when they need it. Since the system is self-service the sales effort (materials management) is reduced. The shelves are refilled as products are sold (parts withdrawn) on the assumption that what has sold will sell again which makes it easy to see how much has been used and to avoid overstocking. The most important feature of a supermarket system is that stocking is triggered by actual demand. In the TPS this signal triggers the 'pull' system of production. [ 1 ]
Market locations are appropriate where there is a desire to communicate customer pull up the supply chain. The aim of the 'market' is to send single unit consumption signals back up the supply chain so that a demand leveling effect occurs. Just as in a supermarket it is possible for someone to decide to cater for a party of 300 from the supermarket so it is possible to decide to suddenly fill ten trucks and send massively distorting signals up those same pathways. Thus the 'market location' can be used as a sort of isolator between actual demand and how supply would like demand to be, an isolator between batch demand spikes and the upstream supply process. [ 2 ]
For example, if the market were positioned at the loading bay, then it would receive 'spikes' of demand whenever a truck comes in to be loaded. Since, in general, one knows in advance when trucks will arrive and what they will require to be loaded onto them, it is possible to spread that demand spike over a chosen period before the truck actually arrives. It is possible to do this by designating a location, say a marked floor area, to be the 'virtual' truck and moving items from the market to the 'virtual truck' smoothly over the chosen period prior to the load onto the actual truck commencing. Smoothly here means that for each item its 'loading' is evenly spread across the period. For regular shipments this period might start the moment the last shipment in that schedule departs the loading bay. This has four key impacts:
This logic can, obviously, be applied upstream of any batch process and not just deliveries to another plant. It is a workaround for the fact that the batch process hasn't been made to flow yet. It therefore has some costs but the benefits in terms of reducing the three wastes should outweigh these.
Toyota use this technique and demand it of their suppliers in order to generate focus on the supply issues it uncovers. They then demand the preparation of loads for more frequent 'virtual' trucks than will actually appear in order to raise this pressure (see Frequent deliveries ).
At low stocking levels for some items the 'market location' can require Just in Sequence supply rather than Just in Time . | https://en.wikipedia.org/wiki/Manufacturing_supermarket |
Many-body localization (MBL) is a dynamical phenomenon occurring in isolated many-body quantum systems. It is characterized by the system failing to reach thermal equilibrium , and retaining a memory of its initial condition in local observables for infinite times. [ 1 ]
Textbook quantum statistical mechanics [ 2 ] assumes that systems go to thermal equilibrium ( thermalization ). The process of thermalization erases local memory of the initial conditions. In textbooks, thermalization is ensured by coupling the system to an external environment or "reservoir," with which the system can exchange energy. What happens if the system is isolated from the environment, and evolves according to its own Schrödinger equation ? Does the system still thermalize?
Quantum mechanical time evolution is unitary and formally preserves all information about the initial condition in the quantum state at all times. However, a quantum system generically contains a macroscopic number of degrees of freedom, but can only be probed through few-body measurements which are local in real space. The meaningful question then becomes whether accessible local measurements display thermalization.
This question can be formalized by considering the quantum mechanical density matrix ρ of the system. If the system is divided into a subregion A (the region being probed) and its complement B (everything else), then all information that can be extracted by measurements made on A alone is encoded in the reduced density matrix ρ A = Tr B ρ ( t ) {\displaystyle \rho _{A}=\operatorname {Tr} _{B}\rho (t)} . If, in the long time limit, ρ A ( t ) {\displaystyle \rho _{A}(t)} approaches a thermal density matrix at a temperature set by the energy density in the state, then the system has "thermalized," and no local information about the initial condition can be extracted from local measurements. This process of "quantum thermalization" may be understood in terms of B acting as a reservoir for A . In this perspective, the entanglement entropy S = − Tr ( ρ A log ρ A ) {\displaystyle S=-\operatorname {Tr} (\rho _{A}\log \rho _{A})} of a thermalizing system in a pure state plays the role of thermal entropy. [ 3 ] [ 4 ] [ 5 ] Thermalizing systems therefore generically have extensive or "volume law" entanglement entropy at any non-zero temperature. [ 6 ] [ 7 ] [ 8 ] They also generically obey the eigenstate thermalization hypothesis (ETH). [ 9 ] [ 10 ] [ 11 ]
In contrast, if ρ A ( T ) {\displaystyle \rho _{A}(T)} fails to approach a thermal density matrix even in the long time limit, and remains instead close to its initial condition ρ A ( 0 ) {\displaystyle \rho _{A}(0)} , then the system retains forever a memory of its initial condition in local observables. This latter possibility is referred to as "many body localization," and involves B failing to act as a reservoir for A . A system in a many body localized phase exhibits MBL, and continues to exhibit MBL even when subject to arbitrary local perturbations. Eigenstates of systems exhibiting MBL do not obey the ETH, and generically follow an "area law" for entanglement entropy (i.e. the entanglement entropy scales with the surface area of subregion A ). A brief list of properties differentiating thermalizing and MBL systems is provided below.
MBL was first proposed by P.W. Anderson in 1958 [ 22 ] as a possibility that could arise in strongly disordered quantum systems. The basic idea was that if particles all live in a random energy landscape, then any rearrangement of particles would change the energy of the system. Since energy is a conserved quantity in quantum mechanics, such a process can only be virtual and cannot lead to any transport of particle number or energy.
While localization for single particle systems was demonstrated already in Anderson's original paper (coming to be known as Anderson localization ), the existence of the phenomenon for many particle systems remained a conjecture for decades. In 1980 Fleishman and Anderson [ 23 ] demonstrated the phenomenon survived the addition of interactions to lowest order in perturbation theory . In a 1998 study, [ 24 ] the analysis was extended to all orders in perturbation theory, in a zero-dimensional system , and the MBL phenomenon was shown to survive. In 2005 [ 25 ] and 2006, [ 26 ] this was extended to high orders in perturbation theory in high dimensional systems. MBL was argued to survive at least at low energy density. A series of numerical works [ 27 ] [ 14 ] [ 28 ] [ 29 ] provided further evidence for the phenomenon in one dimensional systems, at all energy densities (“infinite temperature”). Finally, in 2014 [ 30 ] Imbrie presented a proof of MBL for certain one dimensional spin chains with strong disorder, with the localization being stable to arbitrary local perturbations – i.e. the systems were shown to be in a many body localized phase.
It is now believed that MBL can arise also in periodically driven "Floquet" systems where energy is conserved only modulo the drive frequency. [ 31 ] [ 32 ] [ 33 ]
Many body localized systems exhibit a phenomenon known as emergent integrability. In a non-interacting Anderson insulator, the occupation number of each localized single particle orbital is separately a local integral of motion. It was conjectured [ 34 ] [ 35 ] (and proven by Imbrie) that a similar extensive set of local integrals of motion should also exist in the MBL phase. Consider for specificity a one dimensional spin-1/2 chain with Hamiltonian
where X , Y and Z are Pauli operators, and h I are random variables drawn from a distribution of some width W . When the disorder is strong enough ( W > W c ) that all eigenstates are localized, then there exists a local unitary transformation to new variables τ such that
where τ are Pauli operators that are related to the physical Pauli operators by a local unitary transformation, the ... indicates additional terms which only involve τ z operators, and the coefficients fall off exponentially with distance. This Hamiltonian manifestly contains an extensive number of localized integrals of motion or "l-bits" (the operators τ z i , which all commute with the Hamiltonian). If the original Hamiltonian is perturbed, the l-bits get redefined, but the integrable structure survives.
MBL enables the formation of exotic forms of quantum order that could not arise in thermal equilibrium, through the phenomenon of localization-protected quantum order . [ 36 ] A form of localization-protected quantum order, arising only in periodically driven systems, is the Floquet time crystal . [ 37 ] [ 38 ] [ 39 ] [ 40 ] [ 41 ]
A number of experiments have been reported observing the MBL phenomenon. [ 42 ] [ 43 ] [ 44 ] [ 45 ] Most of these experiments involve synthetic quantum systems, such as assemblies of ultracold atoms or trapped ions . [ 46 ] Experimental explorations of the phenomenon in solid state systems are still in their infancy. | https://en.wikipedia.org/wiki/Many-body_localization |
Many-sorted logic can reflect formally our intention not to handle the universe as a homogeneous collection of objects, but to partition it in a way that is similar to types in typeful programming . Both functional and assertive " parts of speech " in the language of the logic reflect this typeful partitioning of the universe, even on the syntax level: substitution and argument passing can be done only accordingly, respecting the "sorts".
There are various ways to formalize the intention mentioned above; a many-sorted logic is any package of information which fulfils it. In most cases, the following are given:
The domain of discourse of any structure of that signature is then fragmented into disjoint subsets, one for every sort.
When reasoning about biological organisms, it is useful to distinguish two sorts: p l a n t {\displaystyle \mathrm {plant} } and a n i m a l {\displaystyle \mathrm {animal} } . While a function m o t h e r : a n i m a l → a n i m a l {\displaystyle \mathrm {mother} \colon \mathrm {animal} \to \mathrm {animal} } makes sense, a similar function m o t h e r : p l a n t → p l a n t {\displaystyle \mathrm {mother} \colon \mathrm {plant} \to \mathrm {plant} } usually does not. Many-sorted logic allows one to have terms like m o t h e r ( l a s s i e ) {\displaystyle \mathrm {mother} (\mathrm {lassie} )} , but to discard terms like m o t h e r ( m y _ f a v o r i t e _ o a k ) {\displaystyle \mathrm {mother} (\mathrm {my\_favorite\_oak} )} as syntactically ill-formed.
The algebraization of many-sorted logic is explained in an article by Caleiro and Gonçalves, [ 1 ] which generalizes abstract algebraic logic to the many-sorted case, but can also be used as introductory material.
While many-sorted logic requires two distinct sorts to have disjoint universe sets, order-sorted logic allows one sort s 1 {\displaystyle s_{1}} to be declared a subsort of another sort s 2 {\displaystyle s_{2}} , usually by writing s 1 ⊆ s 2 {\displaystyle s_{1}\subseteq s_{2}} or similar syntax. In the above biology example, it is desirable to declare
and so on; cf. picture.
Wherever a term of some sort s {\displaystyle s} is required, a term of any subsort of s {\displaystyle s} may be supplied instead ( Liskov substitution principle ). For example, assuming a function declaration mother : animal ⟶ animal {\displaystyle {\text{mother}}:{\text{animal}}\longrightarrow {\text{animal}}} , and a constant declaration lassie : dog {\displaystyle {\text{lassie}}:{\text{dog}}} , the term mother ( lassie ) {\displaystyle {\text{mother}}({\text{lassie}})} is perfectly valid and has the sort animal {\displaystyle {\text{animal}}} . In order to supply the information that the mother of a dog is a dog in turn, another declaration mother : dog ⟶ dog {\displaystyle {\text{mother}}:{\text{dog}}\longrightarrow {\text{dog}}} may be issued; this is called function overloading , similar to overloading in programming languages .
Order-sorted logic can be translated into unsorted logic, using a unary predicate p i ( x ) {\displaystyle p_{i}(x)} for each sort s i {\displaystyle s_{i}} , and an axiom ∀ x ( p i ( x ) → p j ( x ) ) {\displaystyle \forall x(p_{i}(x)\rightarrow p_{j}(x))} for each subsort declaration s i ⊆ s j {\displaystyle s_{i}\subseteq s_{j}} . The reverse approach was successful in automated theorem proving: in 1985, Christoph Walther could solve a then benchmark problem by translating it into order-sorted logic, thereby boiling it down an order of magnitude, as many unary predicates turned into sorts. [ 2 ]
In order to incorporate order-sorted logic into a clause-based automated theorem prover, a corresponding order-sorted unification algorithm is necessary, which requires for any two declared sorts s 1 , s 2 {\displaystyle s_{1},s_{2}} their intersection s 1 ∩ s 2 {\displaystyle s_{1}\cap s_{2}} to be declared, too: if x 1 {\displaystyle x_{1}} and x 2 {\displaystyle x_{2}} are variables of sort s 1 {\displaystyle s_{1}} and s 2 {\displaystyle s_{2}} , respectively, the equation x 1 = ? x 2 {\displaystyle x_{1}{\stackrel {?}{=}}\,x_{2}} has the solution { x 1 = x , x 2 = x } {\displaystyle \{x_{1}=x,\;x_{2}=x\}} , where x : s 1 ∩ s 2 {\displaystyle x:s_{1}\cap s_{2}} .
Smolka generalized order-sorted logic to allow for parametric polymorphism . [ 3 ] [ 4 ] In his framework, subsort declarations are propagated to complex type expressions.
As a programming example, a parametric sort list ( X ) {\displaystyle {\text{list}}(X)} may be declared (with X {\displaystyle X} being a type parameter as in a C++ template ), and from a subsort declaration int ⊆ float {\displaystyle {\text{int}}\subseteq {\text{float}}} the relation list ( int ) ⊆ list ( float ) {\displaystyle {\text{list}}({\text{int}})\subseteq {\text{list}}({\text{float}})} is automatically inferred, meaning that each list of integers is also a list of floats.
Schmidt-Schauß generalized order-sorted logic to allow for term declarations. [ 5 ] As an example, assuming subsort declarations even ⊆ int {\displaystyle {\text{even}}\subseteq {\text{int}}} and odd ⊆ int {\displaystyle {\text{odd}}\subseteq {\text{int}}} , a term declaration like ∀ i : int . ( i + i ) : even {\displaystyle \forall i:{\text{int}}.\;(i+i):{\text{even}}} allows to declare a property of integer addition that could not be expressed by ordinary overloading.
Early papers on many-sorted logic include: | https://en.wikipedia.org/wiki/Many-sorted_logic |
Many antennas [ 1 ] is a smart antenna technique which overcomes the performance limitation of single user multiple-input multiple-output (MIMO) techniques. In cellular communication , the maximum number of considered antennas for downlink is 2 and 4 to support 3GPP Long Term Evolution (LTE) and IMT Advanced requirements, respectively. Since the available spectrum band will probably be limited while the data rate requirement will continuously increase beyond IMT-A to support the mobile multimedia services, it is highly probable that the number of transmit antennas at the base station must be increased to 8–64 or more. The installation of many antennas at single base stations introduced many challenges and required development of several high technologies: a new SDMA engine, a new beamforming algorithm and a new antenna array.
The table summarizes the recent history of multiple antenna techniques in cellular communications. The table includes the future prediction as well for IMT-A and beyond. | https://en.wikipedia.org/wiki/Many_antennas |
In the field of control engineering , a map-based controller is a controller whose outputs are based on values derived from a pre-defined lookup table . [ 1 ] The inputs to the controller are usually values taken from one or more sensors and are used to index the output values in the lookup table. [ 1 ] By effectively placing the transfer function as discrete entries within a lookup table, engineers are free to modify smaller sections or update the whole list of entries as required. [ 1 ] | https://en.wikipedia.org/wiki/Map-based_controller |
MapHook is a location-based journal and social networking application that is operated by MapHook Inc., a software applications development firm based in Dulles, Virginia .
MapHook combines GPS and mapping technologies to allow users to create geo-tagged digital memories about events, locations, and activities. These geo-tagged "hooks" contain user reviews, anecdotal information, available business details, and user-created images pertaining to the selected location. [ 1 ] Hooks are then published per user specifications to the public or select individuals. MapHook also seamlessly integrates points of interest within a user's selected vicinities with third-party content from Wikipedia , Groupon , Yelp , Foursquare , and Twitter . [ 2 ]
MapHook was launched in July 2010. [ 3 ] [ 4 ]
In August 2010, Gulf Caravan, an advocacy group from St. Louis, MO , selected MapHook to help create awareness about the businesses impacted by the Deepwater Horizon oil spill . [ 5 ]
In April 2011, MapHook joined with Groupon and began displaying regional Groupon offerings by user location. [ 6 ]
In August 2011, MapHook added the ability to attach YouTube videos to "hooks." MapHook also introduced the "Groups" concept, which allowed for the creation of user communities with user-set levels of privacy. MapHook also connected with Facebook , Twitter , and Google+ in order to merge with other social networking platforms. [ 7 ]
In September 2011, MapHook partnered with ThinkGeek and their “Timmy the Monkey Sticker Map Project,” which documents the global reach of ThinkGeek customers by using MapHook. [ 8 ] [ 9 ]
In March 2012, MapHook partnered with the World Wildlife Fund and their "Tigers or Toilet Paper" project , which aims to draw closer attention to the deforestation and ruin of the Sumatran tiger ’s habitat by having users create hooks to spread awareness about the paper products being sold in their area. [ 10 ] [ 11 ] MapHook and the World Wildlife Fund also teamed together again for Earth Hour , which took place in 2012 on March 31. [ 12 ] As part of the Earth Hour MapHook Project , the World Wildlife Fund asked Earth Hour participants to post hooks on MapHook in order to chart participation and share experiences. [ 13 ]
By 2014, users added “hooks” to MapHook from 50 countries around the world. [ 2 ]
Upon its release, MapHook was included in Gizmodo's "This Week's Best Apps" list, [ 14 ] TIME's "App of the Week", [ 15 ] and NY Times' "Quick Calls" list. [ 16 ] | https://en.wikipedia.org/wiki/MapHook |
MapInfo Interchange Format is a map and database exporting/importing file format of MapInfo software product. The MIF-file filename usually ends with .mif -suffix.
MIF-files usual have a related MID-file. The filename of a MID-file usually ends
with .mid -suffix. If MID-file not exist, on import, MapInfo stores empty data to every data columns of created " Mapinfo Table ".
MIF-file contains Block with the description of attributive Data-columns and Blocks that stores Geomentry Objects.
MID-file is CSV -like format to store the attributive Data. Each line in MID-file is related with the same order Geometry Block (Geometry Object) in MIF-file.
This computing article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/MapInfo_Interchange_Format |
In topology and graph theory , a map is a subdivision of a surface such as the Euclidean plane into interior-disjoint regions,
formed by embedding a graph onto the surface and forming connected components (faces) of the complement of the graph.
That is, it is a tessellation of the surface. A map graph is a graph derived from a map by creating a vertex for each face and an edge for each pair of faces that meet at a vertex or edge of the embedded graph. [ 1 ]
This topology-related article is a stub . You can help Wikipedia by expanding it .
This graph theory -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Map_(graph_theory) |
In mathematics , a map or mapping is a function in its general sense. [ 1 ] These terms may have originated as from the process of making a geographical map : mapping the Earth surface to a sheet of paper. [ 2 ]
The term map may be used to distinguish some special types of functions, such as homomorphisms . For example, a linear map is a homomorphism of vector spaces , while the term linear function may have this meaning or it may mean a linear polynomial . [ 3 ] [ 4 ] In category theory , a map may refer to a morphism . [ 2 ] The term transformation can be used interchangeably, [ 2 ] but transformation often refers to a function from a set to itself. There are also a few less common uses in logic and graph theory .
In many branches of mathematics, the term map is used to mean a function , [ 5 ] [ 6 ] [ 7 ] sometimes with a specific property of particular importance to that branch. For instance, a "map" is a " continuous function " in topology , a " linear transformation " in linear algebra , etc.
Some authors, such as Serge Lang , [ 8 ] use "function" only to refer to maps in which the codomain is a set of numbers (i.e. a subset of R or C ), and reserve the term mapping for more general functions.
Maps of certain kinds have been given specific names. These include homomorphisms in algebra , isometries in geometry , operators in analysis and representations in group theory . [ 2 ]
In the theory of dynamical systems , a map denotes an evolution function used to create discrete dynamical systems .
A partial map is a partial function . Related terminology such as domain , codomain , injective , and continuous can be applied equally to maps and functions, with the same meaning. All these usages can be applied to "maps" as general functions or as functions with special properties.
In category theory, "map" is often used as a synonym for " morphism " or "arrow", which is a structure-respecting function and thus may imply more structure than "function" does. [ 9 ] For example, a morphism f : X → Y {\displaystyle f:\,X\to Y} in a concrete category (i.e. a morphism that can be viewed as a function) carries with it the information of its domain (the source X {\displaystyle X} of the morphism) and its codomain (the target Y {\displaystyle Y} ). In the widely used definition of a function f : X → Y {\displaystyle f:X\to Y} , f {\displaystyle f} is a subset of X × Y {\displaystyle X\times Y} consisting of all the pairs ( x , f ( x ) ) {\displaystyle (x,f(x))} for x ∈ X {\displaystyle x\in X} . In this sense, the function does not capture the set Y {\displaystyle Y} that is used as the codomain; only the range f ( X ) {\displaystyle f(X)} is determined by the function. | https://en.wikipedia.org/wiki/Map_(mathematics) |
Map algebra is an algebra for manipulating geographic data , primarily fields . Developed by Dr. Dana Tomlin and others in the late 1970s, it is a set of primitive operations in a geographic information system (GIS) which allows one or more raster layers ("maps") of similar dimensions to produce a new raster layer (map) using mathematical or other operations such as addition, subtraction etc.
Prior to the advent of GIS, the overlay principle had developed as a method of literally superimposing different thematic maps (typically an isarithmic map or a chorochromatic map ) drawn on transparent film (e.g., cellulose acetate ) to see the interactions and find locations with specific combinations of characteristics. [ 1 ] The technique was largely developed by landscape architects and city planners , starting with Warren Manning and further refined and popularized by Jaqueline Tyrwhitt , Ian McHarg and others during the 1950s and 1960s. [ 2 ] [ 3 ] [ 4 ]
In the mid-1970s, landscape architecture student C. Dana Tomlin developed some of the first tools for overlay analysis in raster as part of the IMGRID project at the Harvard Laboratory for Computer Graphics and Spatial Analysis , which he eventually transformed into the Map Analysis Package (MAP), a popular raster GIS during the 1980s. While a graduate student at Yale University , Tomlin and Joseph K. Berry re-conceptualized these tools as a mathematical model, which by 1983 they were calling "map algebra." [ 5 ] [ 6 ] This effort was part of Tomlin's development of cartographic modeling , a technique for using these raster operations to implement the manual overlay procedures of McHarg. Although the basic operations were defined in his 1983 PhD dissertation, Tomlin had refined the principles of map algebra and cartographic modeling into their current form by 1990. [ 7 ] [ 8 ] Although the term cartographic modeling has not gained as wide an acceptance as synonyms such as suitability analysis , suitability modeling and multi-criteria decision making, "map algebra" became a core part of GIS. Because Tomlin released the source code to MAP, its algorithms were implemented (with varying degrees of modification) as the analysis toolkit of almost every raster GIS software package starting in the 1980s, including GRASS , IDRISI (now TerrSet ), and the GRID module of ARC/INFO (later incorporated into the Spatial Analyst module of ArcGIS).
This widespread implementation further led to the development of many extensions to map algebra, following efforts to extend the raster data model , such as adding new functionality for analyzing spatiotemporal and three-dimensional grids. [ 9 ] [ 10 ]
Like other algebraic structures , map algebra consists of a set of objects (the domain ) and a set of operations that manipulate those objects with closure (i.e., the result of an operation is itself in the domain, not something completely different). In this case, the domain is the set of all possible "maps," which are generally implemented as raster grids . A raster grid is a two-dimensional array of cells (Tomlin called them locations or points ), each cell occupying a square area of geographic space and being coded with a value representing the measured property of a given geographic phenomenon (usually a field ) at that location. Each operation 1) takes one or more raster grids as inputs, 2) creates an output grid with matching cell geometry, 3) scans through each cell of the input grid (or spatially matching cells of multiple inputs), 4) performs the operation on the cell value(s), and writes the result to the corresponding cell in the output grid. [ 7 ] Originally, the inputs and the output grids were required to have the identical cell geometry (i.e., covering the same spatial extent with the same cell arrangement, so that each cell corresponds between inputs and outputs), but many modern GIS implementations do not require this, performing interpolation as needed to derive values at corresponding locations. [ 11 ]
Tomlin classified the many possible map algebra operations into three types, to which some systems add a fourth: [ 12 ]
Several GIS software packages implement map algebra concepts, including PostGIS , ERDAS Imagine , QGIS , GRASS GIS , TerrSet , PCRaster , and ArcGIS .
In Tomlin's original formulation of cartographic modeling in the Map Analysis Package, he designed a simple procedural language around the algebra operators to allow them to be combined into a complete procedure with additional structures such as conditional branching and looping. [ 8 ] However, in most modern implementations, map algebra operations are typically one component of a general procedural processing system, such as a visual modeling tool or a scripting language. For example, ArcGIS implements Map Algebra in both its visual ModelBuilder tool and in Python . Here, Python's overloading capability [ 15 ] allows simple operators and functions to be used for raster grids. For example, rasters can be multiplied using the same "*" arithmetic operator used for multiplying numbers. [ 16 ]
Here a modern MapAlgebra implementation, embedding map algebra expressions into SQL (of PostGIS and others), see function ST_MapAlgebra() guide :
Here are some examples in MapBasic , the scripting language for MapInfo Professional : | https://en.wikipedia.org/wiki/Map_algebra |
The Map Communication Model is a theory in cartography that characterizes mapping as a process of transmitting geographic information via the map from the cartographer to the end-user. [ 1 ] It was perhaps the first paradigm to gain widespread acceptance in cartography in the international cartographic community and between academic and practising cartographers. [ 2 ]
By the mid-20th century, according to Crampton (2001) "cartographers as Arthur H. Robinson and others had begun to see the map as primarily a communication tool, and so developed a specific model for map communication, the map communication model (MCM)". [ 3 ] This model, according to Andrews (1988) "can be grouped with the other major communication models of the time, such as the Shannon-Weaver and Lasswell models of communication. The map communication model led to a whole new body of research, methodologies and map design paradigms" [ 4 ]
One of the implications of this communication model according to Crampton (2001) "endorsed an “epistemic break” that shifted our understandings of maps as communication systems to investigating them in terms of fields of power relations and exploring the “mapping environments in which knowledge is constructed”... This involved examining the social contexts in which maps were both produced and used, a departure from simply seeing maps as artifacts to be understood apart from this context". [ 3 ]
A second implication of this model is the presumption inherited from positivism that it is possible to separate facts from values. As Harley stated: Maps are never value-free images; except in the narrowest Euclidean sense they are not in themselves either true or false. Both in the selectivity of their content and in their signs and styles of representation maps are a way of conceiving, articulating, and structuring the human world which is biased towards, promoted by, and exerts influence upon particular sets of social relations. By accepting such premises it becomes easier to see how appropriate they are to manipulation by the powerful in society. [ 5 ]
Although this was a postwar discovery, the Map Communication Model (MCM) has its roots in information theory developed in the telephone industry before the war began. Mathematician, inventor, and teacher Claude Shannon worked at Bell Labs after completing his Ph.D. at the Massachusetts Institute of Technology in 1940. Shannon applied mathematical theory to information and demonstrated that communication could be reduced to binary digits ( bits ) of positive and negative circuits. This information could be coded and transmitted across a noisy interface without losing any meaning. Once the information was received it was then decoded by the listener; the integrity of the information remained intact. In producing meaningful sounds that could be measured for quality, Shannon produced the beginning of information theory and digital communication through circuits of on and off switches .
Shannon developed his ideas more thoroughly in the 1940s at the same time that geographer and cartographer Arthur H. Robinson returned from the Second World War during which he had served as cartographer for the military. Robinson found that cartographers were significantly limited because artists could make more effective maps than geographers. Upon returning from the war, Robinson worked to remedy this problem at Ohio State University where he was a graduate student. His The Look of Maps emphasizes the importance of lettering, map design, map structure, color, and technique.
Information theory helped turn the map into a medium of communicating information. Although Robinson never articulated a map model that could govern the new scientific pursuit of maps, his role in the war led to an understanding of the practical need for maps based on science not art. Robinson opened the door for others to apply Shannon’s Mathematical Theory of Communication to the design of maps. British geographer Christopher Board developed the first MCM in 1967 but it was cumbersome and poorly measured a map’s information quality. The Czech Geographer Kolácný’s 1969 version made several key improvements to Board’s model. These versions of the MCM helped cartographers realize the problems that Robinson noted as a war cartographer and helped articulate the discipline in terms of science. | https://en.wikipedia.org/wiki/Map_communication_model |
Map matching is the problem of how to match recorded geographic coordinates to a logical model of the real world, typically using some form of Geographic Information System . The most common approach is to take recorded, serial location points (e.g. from GPS ) and relate them to edges in an existing street graph (network), usually in a sorted list representing the travel of a user or vehicle. Matching observations to a logical model in this way has applications in satellites navigation , GPS tracking of freight , and transportation engineering .
Map matching algorithms can be divided in real-time and offline algorithms. Real-time algorithms associate the position during the recording process to the road network. Offline algorithms are used after the data is recorded and are then matched to the road network. [ 1 ] Real-time applications can only calculate based upon the points prior to a given time (as opposed to those of a whole journey), but are intended to be used in 'live' environments. This brings a compromise of performance over accuracy. Offline applications can consider all points and so can tolerate slower performance in favour of accuracy. However, the defects on low accuracy can be reduced due to integration of spatio-temporal proximity and improved weighted circle algorithms. [ 2 ]
Uses for map-matching algorithms range from the immediate and practical, such as applications designed for guiding travellers, to the analytical, such as generating detailed inputs for traffic analysis models and the like.
Probably the most common use of map-matching is where a traveller has some mobile computer giving him or her directions across a street network. In order to give accurate directions, the device must know exactly where in the street network the user is. A GPS location has positional error though, so picking the nearest street segment and routing from there will likely not work. Instead, the history of locations reported by the GPS can be used to guess a plausible route and infer the current location more accurately.
Other uses, more analytical in nature, include:
There are other examples [ 3 ] and this subject is still undergoing active research and development. [ 4 ] [ 5 ] [ 6 ] [ 7 ]
The earliest approached to solve the map matching problem based on similarity between points' curve and the road curve. [ 8 ]
Topological map matching aligns GPS points with a road network by considering the connectivity and relationships between road segments. It accounts for the structure of the network, path constraints, and the sequence of GPS points to provide accurate and realistic route matching, especially in complex environments.
Advanced map-matching algorithms, including those based on Fuzzy Logic, Hidden Markov Models (HMM), and Kalman filters, significantly enhance the accuracy of GPS point location estimation. However, achieving this level of precision often requires substantial processing time. [ 9 ]
Map matching is described as a hidden Markov model where emission probability is a confidence of a point to belong a single segment, and the transition probability is presented as possibility of a point to move from one segment to another within a given time. [ 10 ] [ 11 ]
Map matching is implemented in a variety of programs, [ 12 ] [ 13 ] including the open-source GraphHopper and Open Source Routing Machine routing engines. [ 14 ] It is also included in a variety of proprietary programs and mapping/routing applications. | https://en.wikipedia.org/wiki/Map_matching |
A map symbol or cartographic symbol is a graphical device used to visually represent a real-world feature on a map , working in the same fashion as other forms of symbols . Map symbols may include point markers, lines, regions, continuous fields , or text; these can be designed visually in their shape, size, color, pattern, and other graphic variables to represent a variety of information about each phenomenon being represented.
Map symbols simultaneously serve several purposes:
Symbols are used to represent geographic phenomena, which exist in, and are represented by, a variety of spatial forms. Different kinds of symbols are used to portray different spatial forms. [ 1 ] Phenomena can be categorized a number of ways, but two are most relevant to symbology: ontological form and dimensionality. When a symbol is representing a property of the phenomenon as well as its location, the choice of symbol also depends on the nature of that property, usually classified as a Level of measurement .
Geographic phenomena can be categorized into objects , which are recognizable as a unified whole with a relevant boundary and shape; and masses , in which the notion of boundary and wholeness are not relevant to their identity. Features such as buildings, cities, roads, lakes, and countries are geographic objects that are often portrayed on maps using symbols. Mass phenomena include air, water, vegetation, and rock. These are rarely represented directly on maps; instead, map symbols portray their properties, which usually take the form of geographic fields , such as temperature, moisture content, density, and composition.
The number of spatial dimensions needed to represent a phenomenon determine a choice of Geometric primitive ; each type of geometric primitive is drawn with a different type of visual symbol. [ 2 ]
Fill (color, opacity, texture)
Interior (color, opacity, texture)
The dimensionality of a map symbol representing a feature may or may not be the same as the dimensionality of the feature in the real world; discrepancies are the result of cartographic generalization to simplify features based on purpose and scale. For example, a three-dimensional road is often represented as a one-dimensional line symbol, while two-dimensional cities are frequently represented by zero-dimensional points. [ 3 ]
Many map symbols visualize not just the location and shape of a geographic phenomenon, but also one or more of its properties or attributes. Geographers and cartographers usually categorize properties according to the classification system of Stanley Smith Stevens , or some revision thereof, such as that of Chrisman. [ 4 ] Different kinds of symbols and visual variables are better at intuitively representing some levels than others, especially when the visual variable portrays the same kind of differences as the represented attribute. [ 3 ]
In cartography , the principles of cognition are important since they explain why certain map symbols work. [ 5 ] In the past, mapmakers did not care why the symbols worked. This behaviorist view treats the human brain like a black box. Modern cartographers are curious why certain symbols are the most effective. This should help develop a theoretical basis for how brains recognize symbols and, in turn, provide a platform for creating new symbols.
According to semiotics , specifically the Semiotic theory of Charles Sanders Peirce , map symbols are "read" by map users when they make a connection between the graphic mark on the map (the sign ), a general or specific concept (the interpretant ), and a particular feature of the real world (the object or referent ). Map symbols can thus be categorized by how they suggest this connection: [ 6 ] [ 7 ]
A map symbol is created by altering the visual appearance of a feature, whether a point, line, or region; this appearance can be controlled using one or more visual variables . Jacques Bertin , a French cartographer, developed the concept of visual variables in his 1967 book, "Sémiologie Graphique." [ 8 ] Bertin identified seven main categories of visual variables: position, size, shape, value, color, orientation, and texture/grain. [ 9 ] Since then, cartographers have modified and expanded this set. [ 10 ]
Each of these variables may be employed to convey information, to provide contrast between different features and layers, to establish figure-ground contrast and a clear visual hierarchy , or add to the aesthetic appeal of the map. [ 11 ] The most common set of visual variables, as canonized in cartography textbooks and the Geographic Information Science and Technology Body of Knowledge , [ 3 ] includes the following:
Cartographers have also proposed analogous sets of controllable variables for animated maps, [ 14 ] [ 2 ] haptic (touch) maps, [ 15 ] and even the use of sound in digital maps. [ 16 ]
An important factor in map symbols is the order in which they are ranked according to their relative importance. This is known as intellectual hierarchy. The most important hierarchy is the thematic symbols and type labels that are directly related to the theme. Next comes the title, subtitle, and legend . [ 1 ] The map must also contain base information, such as boundaries, roads, and place names. Data source and notes should be on all maps. Lastly, the scale, neat lines, and north arrow are the least important of the hierarchy of the map. From this we see that the symbols are the single most important thing to build a good visual hierarchy that shows proper graphical representation. When producing a map with good visual hierarchy, thematic symbols should be graphically emphasized. A map with a visual hierarchy that is effective attracts the map user's eyes to the symbols with the most important aspects of the map first and to the symbols with the lesser importance later.
The legend of the map also contains important information and all of the thematic symbols of the map. Symbols that need no explanations, or do not coincide with the theme of the map, are normally omitted from the map legend. Thematic symbols directly represent the maps theme and should stand out. [ 17 ]
This article incorporates text by Wiki.GIS.com available under the CC BY-SA 3.0 license. | https://en.wikipedia.org/wiki/Map_symbol |
Maple is a symbolic and numeric computing environment as well as a multi-paradigm programming language . It covers several areas of technical computing, such as symbolic mathematics, numerical analysis, data processing, visualization, and others. A toolbox, MapleSim , adds functionality for multidomain physical modeling and code generation.
Maple's capacity for symbolic computing include those of a general-purpose computer algebra system . For instance, it can manipulate mathematical expressions and find symbolic solutions to
certain problems, such as those arising from ordinary and partial differential equations .
Maple is developed commercially by the Canadian software company Maplesoft . The name 'Maple' is a reference to the software's Canadian heritage .
Users can enter mathematics in traditional mathematical notation . Custom user interfaces can also be created. There is support for numeric computations, to arbitrary precision, as well as symbolic computation and visualization. Examples of symbolic computations are given below.
Maple incorporates a dynamically typed imperative-style programming language (resembling Pascal ), which permits variables of lexical scope . [ 3 ] There are also interfaces to other languages ( C , C# , Fortran , Java , MATLAB , and Visual Basic ), as well as to Microsoft Excel .
Maple supports MathML 2.0, which is a W3C format for representing and interpreting mathematical expressions, including their display in web pages. [ 4 ] There is also functionality for converting expressions from traditional mathematical notation to markup suitable for the typesetting system LaTeX .
Maple is based on a small kernel , written in C , which provides the Maple language. Most functionality is provided by libraries, which come from a variety of sources. Most of the libraries are written in the Maple language; these have viewable source code. Many numerical computations are performed by the NAG Numerical Libraries , ATLAS libraries, or GMP libraries.
Different functionality in Maple requires numerical data in different formats. Symbolic expressions are stored in memory as directed acyclic graphs . The standard interface and calculator interface are written in Java .
The first concept of Maple arose from a meeting in late 1980 at the University of Waterloo . [ 5 ] Researchers at the university wished to purchase a computer powerful enough to run the Lisp-based computer algebra system Macsyma . Instead, they opted to develop their own computer algebra system, named Maple, that would run on lower cost computers. Aiming for portability, they began writing Maple in programming languages from the BCPL family (initially using a subset of B and C , and later on only C). [ 5 ] A first limited version appeared after three weeks, and fuller versions entered mainstream use beginning in 1982. [ 6 ] By the end of 1983, over 50 universities had copies of Maple installed on their machines. [ citation needed ]
In 1984, the research group arranged with Watcom Products Inc to license and distribute the first commercially available version, Maple 3.3. [ 6 ] In 1988 Waterloo Maple Inc. (Maplesoft) was founded. The company's original goal was to manage the distribution of the software, but eventually it grew to have its own R&D department, where most of Maple's development takes place today (the remainder being done at various university laboratories [ 7 ] ).
In 1989, the first graphical user interface for Maple was developed and included with version 4.3 for the Macintosh . X11 and Windows versions of the new interface followed in 1990 with Maple V. In 1992, Maple V Release 2 introduced the Maple "worksheet" that combined text, graphics, and input and typeset output. [ 8 ] In 1994 a special issue of a newsletter created by Maple developers called MapleTech was published. [ 9 ]
In 1999, with the release of Maple 6, Maple included some of the NAG Numerical Libraries . [ 10 ] In 2003, the current "standard" interface was introduced with Maple 9. This interface is primarily written in Java (although portions, such as the rules for typesetting mathematical formulae, are written in the Maple language). The Java interface was criticized for being slow; [ 11 ] improvements have been made in later versions, although the Maple 11 documentation [ 12 ] recommends the previous ("classic") interface for users with less than 500 MB of physical memory.
Between 1995 and 2005 Maple lost significant market share to competitors due to a weaker user interface. [ 13 ] With Maple 10 in 2005, Maple introduced a new "document mode" interface, which has since been further developed across several releases.
In September 2009 Maple and Maplesoft were acquired by the Japanese software retailer Cybernet Systems . [ 14 ]
Features of Maple include: [ 30 ]
The following code, which computes the factorial of a nonnegative integer, is an example of an imperative programming construct within Maple:
Simple functions can also be defined using the "maps to" arrow notation:
Find
Output:
Compute the determinant of a matrix.
The following code numerically calculates the roots of a high-order polynomial:
The same command can also solve systems of equations:
Plot x sin ( x ) {\displaystyle x\sin(x)} with x ranging from -10 to 10:
Plot x 2 + y 2 {\displaystyle x^{2}+y^{2}} with x and y ranging from -1 to 1:
Find functions f that satisfy the integral equation
The Maple engine is used within several other products from Maplesoft :
Listed below are third-party commercial products that no longer use the Maple engine: | https://en.wikipedia.org/wiki/Maple_(software) |
Mapopolis Navigator was a PDA/smartphone GPS navigation software created by Mapopolis. Mapopolis used data from Navteq . [ 1 ] Mapopolis Navigator files use a proprietary format and make it impossible for users to export their custom POIs . [ 2 ] [ 3 ]
Starting in 1999, Mapopolis first released software for the Palm OS and later added software for Pocket PC handhelds and Windows smartphones . Mapopolis created the first real-time traffic service (Mapopolis ClearRoute), providing real-time route updates based on traffic conditions. [ 4 ] [ 5 ]
By April 1, 2007, Mapopolis had discontinued sales of its consumer software. [ 6 ] Map downloads remained available for at least one year past that date for registered users who purchased the product and still did not use up their full 1-year allowance.
This software article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Mapopolis |
The mappae clavicula is a medieval Latin text containing manufacturing recipes for crafts materials, including for metals , glass , mosaics , and dyes and tints for materials. The information and style in the recipes is very terse. Each recipe consists of the names of the ingredients and typically about two sentences on combining the ingredients together. A small minority of the recipes go to about six sentences. The text comes with a short preamble, and other than that it is just recipes. The number of recipes was expanded over the course of the medieval centuries, and some medieval copies have deletions as well as additions, so it is better thought of as a family of texts with a largely common core, not a single text. Most of the Mappae Clavicula recipes are also in medieval Latin in a text known as the Compositiones ad Tingenda (English: "Recipes for Coloring (or Tingeing)"). [ 1 ]
The core was probably originally compiled around AD 600, perhaps in Alexandria in Egypt , in Greek . The core contains items traceable to earlier Alexandrian Greek texts, particularly the Stockholm papyrus and Leiden Papyrus X , which are Greek texts dated to the 2nd or 3rd century AD that contain some of the same and similar recipes. The first few recipes in the Phillipps-Corning manuscript [ 2 ] of the Mappae clavicula were long considered integral, but they form a distinct separate entity, the De coloribus et mixtionibus , which survives (in whole or in part) in at least 62 manuscripts. [ 3 ] The core of the Latin Mappae clavicula is very likely a translation of a Greek text, although the original Greek text (if it existed) does not exist today.
The best manuscripts of the Mappae clavicula date from the eighth to the twelfth century. [ 3 ] [ 4 ]
One of the fullest collections of recipes is in a certain manuscript dated late 12th century in which about 300 recipes are presented. In this manuscript, called the Phillipps-Corning manuscript, some of the names for some materials are Arabic names (e.g. alquibriz from the Arabic for sulphur, atincar from the Arabic for borax, alcazir from the Arabic for tin). [ 2 ] The recipes containing the Arabic names are historically later, and are in all likelihood no earlier than the 12th century. Certain earlier manuscripts have about 200 recipes.
Here is a translation of one recipe for joining tin:
1 part of soap, 1 part of pine resin, 1 part of soda and some borax. Coat the tin with this and heat lightly, as you know how, until it joins together, and quench it while still hot in water. [ 4 ]
The principal manuscripts are:
These are simply among the fullest witnesses - there are dozens more that preserve extracts. [ 3 ]
The title, Mappae clavicula , is absurd, translating approximately as 'the little key to the small cloth'. The best explanation is that it is a mis-translation from a Greek original, in which χειρόκμητον kheirókmēton ('knack' or 'trick of the trade') was mis-read as χειρόμακτρον kheirómaktron ('hand-towel'). [ 5 ] This is consistent with the observation that certain recipes derive from the Greek technical papyri, the Leyden papyrus X and the Stockholm papyrus . | https://en.wikipedia.org/wiki/Mappae_clavicula |
Mapper(2) is a database of transcription factor binding sites in multiple genomes. [ 1 ]
This Biological database -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Mapper(2) |
The maps to symbol, ↦, is a rightward arrow protruding from a vertical bar. It is used in mathematics and in computer science to denote functions . In Z notation , a specification language used in software development, [ 1 ] this symbol is called the maplet arrow and the expression x ↦ y is called a maplet . In separation logic it denotes the contents of a specific cell of memory.
In the Unicode character set, the symbol is code point U+21A6. [ 2 ] | https://en.wikipedia.org/wiki/Maps_to |
MarBEF Data System (Marine Biodiversity and Ecosystem Functioning) was a project of the European Union 's Network of Excellence [ 2 ] which served as a platform to integrate and disseminate knowledge and expertise on marine biodiversity , with informative links to researchers, industry, stakeholders and the general public. The program was funded by the EU and formally ended in 2009. [ 3 ] The data system's online Register of Resources (RoR) includes the details of over 1,000 European marine biology experts and their affiliated institutions and publications. [ 4 ]
MarBEF consisted of 94 European marine institutes and the work done was published in 415 scientific articles. [ 5 ] While the initial MarBEF project has ended, work continues through numerous projects within the MarBEF "umbrella" including, the European Ocean Biogeographic Information System , the European Register of Marine Species , the European Marine Gazetteer , and includes a related Marine Biodiversity Wiki and MarBEF Open Archive . [ 4 ]
The program was funded by the European Union (EU), with € 8,707,000 coming from the European Commission and having a total cost of €8,782,025. [ 1 ] The program was a framework for marine entities, intended to integrate and disseminate the knowledge on marine biodiversity . [ 6 ] It was funded by the Sixth Framework Programme of the EU. [ 7 ] MarBEF consisted of 94 European marine institutes from 24 countries and was coordinated by the Dutch Institute for Ecology (NIOO). [ 1 ]
To accomplish its goals MarBEF participated in and/or supported multiple conferences and workshops to educate and strengthen collaboration between members of the scientific community. [ 8 ] [ 9 ]
The program formally ended in 2009. [ 3 ] While the initial MarBEF project has ended, work continues through numerous projects within the MarBEF "umbrella" including, the European Ocean Biogeographic Information System, the European Register of Marine Species, the European Marine Gazetteer , and includes a related Marine Biodiversity Wiki and MarBEF Open Archive. [ 4 ]
This project continued after the end of MarBEF in 2009. [ 4 ]
European Marine Gazetteer was the MarBEF database of geographic locations (names, information, maps), made available for download by the public. [ 10 ]
The European Register of Marine Species (commonly known by the acronym ERMS) is an authoritative taxonomic list of species occurring in the European marine environment . The ERMS was founded in 1998 by grant from the EU's Marine Science and Technology Programme and the project covers species of the kingdoms Animalia , Plantae , Fungi and Protoctista occurring in the marine environment over a wide geographic range. The marine area within the scope of the ERMS includes the continental shelf seas of Europe as well as the Mediterranean shelf, Baltic Seas and deep-sea areas. [ 11 ] The database contains the records of tens of thousands of marine species. [ 12 ]
The executive committee of the project includes: Dr. Mark Costello (Chief editor) of the University of Auckland , Prof. Philippe Bouchet of the Muséum national d'Histoire naturelle , Prof. Geoff Boxshall of the United Kingdom 's Natural History Museum , and Mr. Ward Appeltans from UNESCO 's Intergovernmental Oceanographic Commission. [ 11 ]
The World Register of Marine Species grew out of the ERMS. [ 13 ] It is primarily funded by the European Union and hosted by the Flanders Marine Institute in Ostend , Belgium. WoRMS has established formal agreements with several other biodiversity projects, including the Global Biodiversity Information Facility and the Encyclopedia of Life . In 2008, WoRMS stated that it hoped to have an up-to-date record of all marine species completed by 2010, the year in which the Census of Marine Life was completed. [ 14 ] | https://en.wikipedia.org/wiki/MarBEF_Data_System |
The Marangoni number ( Ma ) is, as usually defined, the dimensionless number that compares the rate of transport due to Marangoni flows , with the rate of transport of diffusion. The Marangoni effect is flow of a liquid due to gradients in the surface tension of the liquid. Diffusion is of whatever is creating the gradient in the surface tension. Thus as the Marangoni number compares flow and diffusion timescales it is a type of Péclet number .
The Marangoni number is defined as: M a = advective transport rate, due to surface tension gradient diffusive transport rate, of source of gradient {\displaystyle \mathrm {Ma} ={\dfrac {\mbox{advective transport rate, due to surface tension gradient}}{\mbox{diffusive transport rate, of source of gradient}}}}
A common example is surface tension gradients caused by temperature gradients. [ 1 ] Then the relevant diffusion process is that of thermal energy (heat). Another is surface gradients caused by variations in the concentration of surfactants, where the diffusion is now that of surfactant molecules.
The number is named after Italian scientist Carlo Marangoni , although its use dates from the 1950s [ 1 ] [ 2 ] and it was neither discovered nor used by Carlo Marangoni.
The Marangoni number for a simple liquid of viscosity μ {\displaystyle \mu } with a surface tension change Δ γ {\displaystyle \Delta \gamma } over a distance L {\displaystyle L} parallel to the surface, can be estimated as follows. Note that we assume that L {\displaystyle L} is the only length scale in the problem, which in practice implies that the liquid be at least L {\displaystyle L} deep. The transport rate is usually estimated using the equations of Stokes flow , where the fluid velocity is obtained by equating the stress gradient to the viscous dissipation. A surface tension is a force per unit length, so the resulting stress must scale as Δ γ / L {\displaystyle \Delta \gamma /L} , while the viscous stress scales as μ u / L {\displaystyle \mu u/L} , for u {\displaystyle u} the speed of the Marangoni flow. Equating the two we have a flow speed u = Δ γ / μ {\displaystyle u=\Delta \gamma /\mu } . As Ma is a type of Péclet number , it is a velocity times a length, divided by a diffusion constant , D {\displaystyle D} , Here this is the diffusion constant of whatever is causing the surface tension difference. So,
M a = u L D = Δ γ L μ D {\displaystyle \mathrm {Ma} ={\dfrac {uL}{D}}={\dfrac {\Delta \gamma L}{\mu D}}}
A common application is to a layer of liquid, such as water, when there is a temperature difference Δ T {\displaystyle \Delta T} across this layer. This could be due to the liquid evaporating or being heated from below. There is a surface tension at the surface of a liquid that depends on temperature, typically as the temperature increases the surface tension decreases. Thus if due to a small fluctuation temperature, one part of the surface is hotter than another, there will be flow from the hotter part to the colder part, driven by this difference in surface tension, this flow is called the Marangoni effect . This flow will transport thermal energy, and the Marangoni number compares the rate at which thermal energy is transported by this flow to the rate at which thermal energy diffuses.
For a liquid layer of thickness L {\displaystyle L} , viscosity μ {\displaystyle \mu } and thermal diffusivity α {\displaystyle \alpha } , with a surface tension γ {\displaystyle \gamma } which changes with temperature at a rate ∂ γ / ∂ T {\displaystyle \partial \gamma /\partial T} , the Marangoni number can be calculated using the following formula: [ 3 ] M a = − ( ∂ γ / ∂ T ) . L . Δ T μ . α {\displaystyle \mathrm {Ma} =-(\partial \gamma /\partial T).{\frac {L.\Delta T}{\mu .\alpha }}}
When Ma is small thermal diffusion dominates and there is no flow, but for large Ma, flow (convection) occurs, driven by the gradients in the surface tension. This is called Bénard-Marangoni convection. | https://en.wikipedia.org/wiki/Marangoni_number |
Marc, Baron Van Montagu (born 10 November 1933 in Ghent ) is a Belgian molecular biologist . He was full professor and director of the Laboratory of Genetics at the faculty of Sciences at Ghent University ( Belgium ) and scientific director of the genetics department of the Flanders Interuniversity Institute for Biotechnology (VIB). Together with Jozef Schell he founded the biotech company Plant Genetic Systems Inc. (Belgium) in 1982, of which he was scientific director and member of the board of directors. Van Montagu was also involved in founding the biotech company CropDesign , of which he was a board member from 1998 to 2004. He is president of the Public Research and Regulation Initiative (PRRI).
Van Montagu and his colleagues were credited with the discovery of the Ti plasmid . [ 1 ] They described the gene transfer mechanism between Agrobacterium and plants, which resulted in the development of methods to alter Agrobacterium into an efficient delivery system for gene engineering and to create transgenic plants . [ 2 ] They developed plant molecular genetics , in particular molecular mechanisms for cell proliferation and differentiation and response to abiotic stresses (high light, ozone , cold , salt and drought ) and constructed transgenic crops ( tobacco , rape seed , corn ) resistant to insect pest and tolerant to novel herbicides . His work with poplar trees resulted in engineering of trees with improved pulping qualities.
After his retirement as director of the Laboratory of Genetics at Ghent University, Marc Van Montagu created IPBO - International Plant Biotechnology Outreach, VIB-Ghent University, with the mission to foster biotechnological solutions to global agriculture. In 2015 IPBO launched the “Marc and Nora Van Montagu (MNVM) Fund” with focus on sustainable agriculture and agro-industry to the African continent.
Van Montagu has been a foreign associate of the United States National Academy of Sciences since 1986, the agricultural Academy of Russia and France, the Academy of Engineering of Sweden , the Italian Academy of Sciences dei X, the Brazilian Academy of Science, and the Third World Academy of Sciences. He holds eight Doctor Honoris Causa Degrees. In 1990 he was granted the title of Baron by Baudouin of Belgium . His awards include: [ citation needed ] | https://en.wikipedia.org/wiki/Marc_Van_Montagu |
The mineral marcasite , sometimes called " white iron pyrite ", is iron sulfide (FeS 2 ) with orthorhombic crystal structure . It is physically and crystallographically distinct from pyrite , which is iron sulfide with cubic crystal structure . Both structures contain the disulfide S 2 2− ion , having a short bonding distance between the sulfur atoms. The structures differ in how these di-anions are arranged around the Fe 2+ cations . Marcasite is lighter and more brittle than pyrite. Specimens of marcasite often crumble and break up due to the unstable crystal structure .
On fresh surfaces, it is pale yellow to almost white and has a bright metallic luster . It tarnishes to a yellowish or brownish color and gives a black streak. It is a brittle material that cannot be scratched with a knife. The thin, flat, tabular crystals, when joined in groups, are called "cockscombs".
In the late medieval and early modern eras, the word "marcasite" meant all iron sulfides in general, including both pyrite and the mineral marcasite. [ 6 ] The narrower, modern scientific definition for marcasite as specifically orthorhombic iron sulfide dates from 1845. [ 4 ] Jewellery where pyrite is used as the gemstone is called marcasite jewellery ; a term which pre-dates the scientific definition, using the original sense of the word. Marcasite in the scientific sense is not used as a gem due to its brittleness.
Marcasite can be formed as both a primary or a secondary mineral. It typically forms under low-temperature, highly acidic conditions. It occurs in sedimentary rocks ( shales , limestones and low grade coals ) as well as in low temperature hydrothermal veins . Commonly associated minerals include pyrite , pyrrhotite , galena , sphalerite , fluorite , dolomite , and calcite . [ 3 ]
As a primary mineral marcasite forms nodules, concretions, and crystals in a variety of sedimentary rock , such as in the chalk layers found on both sides of the English Channel at Dover , Kent , England , and at Cap Blanc-Nez , Pas de Calais , France , where it forms as sharp individual crystals and crystal groups, and nodules (similar to those shown here). Marcasite is also found in complex sulphide deposits. In the Reocín mine, Cantabria, Spain, appears as crystals grouped in the form of cockscombs . [ 7 ]
As a secondary mineral, it forms by chemical alteration of a primary mineral, such as pyrrhotite or chalcopyrite .
In laboratory experiments, marcasite forms preferentially to pyrite at a pH of less than about 5. [ 8 ] Ab initio calculations suggest that this is due to pyrite having a higher surface energy (thus being less thermodynamically stable) than marcasite at low pH. [ 9 ]
Due to the association of marcasite with low pH, the occurrence of marcasite in sedimentary rocks in the geologic record implies the presence of highly acidic conditions during the formation and early diagenesis of those rocks. However, sedimentary pore waters below the modern ocean are typically buffered at near-neutral to slightly alkaline pH by dissolved carbonate species. [ 10 ] This raises the question of how sedimentary pore waters became sufficiently acidic to promote marcasite formation in the past.
Several theories have been proposed for the formation of early diagenetic marcasite, including: partial oxidation of primary pyrite by molecular oxygen infiltrating from the overlying water column, [ 11 ] and rapid anoxic organic matter decomposition and organic acid generation by fermentation and methanogenesis . [ 12 ]
Blueite (S.H.Emmons): Nickel variety of marcasite, found in Denison Drury and Townships, Sudbury District , Ontario , Canada.
Lonchidite ( August Breithaupt ): Arsenic variety of marcasite, found at Churprinz Friedrich August Erbstolln Mine (Kurprinz Mine), Großschirma Freiberg, Ore Mountains , Saxony , Germany; ideal formula Fe(S, As) 2 .
Synonyms for this variety:
Sperkise : designates a marcasite having twin spearhead crystal on {101}. Sperkise derives from the German Speerkies ( Speer meaning spear and Kies gravel or stone). This twin is very common in the marcasite of a chalky origin, particularly those from the Cap Blanc-Nez .
Marcasite reacts more readily than pyrite under conditions of high humidity. The product of this disintegration is iron(II) sulfate and sulfuric acid . The hydrous iron sulfate forms a white powder consisting of the mineral melanterite , FeSO 4 ·7H 2 O. [ 13 ]
This disintegration of marcasite in mineral collections is known as " pyrite decay ". When a specimen goes through pyrite decay, the marcasite reacts with moisture and oxygen in the air, the sulfur oxidizing and combining with water to produce sulfuric acid that attacks other sulfide minerals and mineral labels. Low humidity (less than 60%) storage conditions prevents or slows the reaction. [ 14 ] [ 15 ] | https://en.wikipedia.org/wiki/Marcasite |
Marcel-Paul "Marco" Schützenberger (24 October 1920 – 29 July 1996) was a French mathematician and Doctor of Medicine. He worked in the fields of formal language , combinatorics , and information theory . [ 1 ] In addition to his formal results in mathematics , he was "deeply involved in [a] struggle against the votaries of [neo-]Darwinism ", [ 2 ] a stance which has resulted in some mixed reactions from his peers and from critics of his stance on evolution . Several notable theorems and objects in mathematics as well as computer science bear his name (for example Schutzenberger group or the Chomsky–Schützenberger hierarchy ). Paul Schützenberger was his great-grandfather.
In the late 1940s, he was briefly married to the psychologist Anne Ancelin Schützenberger . [ 3 ]
Schützenberger's first doctorate, in medicine, was awarded in 1948 from the Faculté de Médecine de Paris . [ 4 ] His doctoral thesis, on the statistical study of biological sex at birth, was distinguished by the Baron Larrey Prize from the French Academy of Medicine . [ 5 ]
Biologist Jaques Besson, a co-author with Schützenberger on a biological topic, [ 6 ] while noting that Schützenberger is perhaps most remembered for work in pure mathematical fields, credits him [ 5 ] for likely being responsible for the introduction of statistical sequential analysis in French hospital practice. [ 7 ]
Schützenberger's second doctorate was awarded in 1953 through the Paris Institute of Statistics . [ 8 ] This work, developed from earlier results [ 9 ] [ 10 ] is counted amongst the early influential French academic work in information theory. [ 11 ] His later impact in both linguistics and combinatorics is reflected by two theorems in formal linguistics (the Chomsky–Schützenberger enumeration theorem [ 12 ] and the Chomsky–Schützenberger representation theorem ), and one in combinatorics (the Schützenberger theorem ). With Alain Lascoux , Schützenberger is credited with the foundation of the notion of the plactic monoid , [ 13 ] [ 14 ] reflected in the name of the combinatorial structure called by some the Lascoux–Schützenberger tree. [ 15 ] [ 16 ] Relatedly, they invented Schubert polynomials .
In automata theory , Schützenberger is credited with first defining (what later became known as) weighted automata , the first studied model of automata which compute a quantitative output. [ 17 ]
The mathematician Dominique Perrin credited Schützenberger with "deeply [influencing] the theory of semigroups" and "deep results on rational functions and transducers", amongst other contributions to mathematics. [ 1 ]
After his death, two journals in theoretical mathematics dedicated issues to Schützenberger's memory. He was commemorated in this manner by Theoretical Computer Science in 1998 [ 18 ] and again by the International Journal of Algebra and Computation in 1999. [ 19 ]
The mathematician David Berlinski provided this dedication in his 2000 book The Advent of The Algorithm: The Idea that Rules the World : À la mémoire de mon ami . . M. P. Schützenberger, 1921-1996.
For the complete list of his papers, see: Papers
The Complete Works of Marcel-Paul Schützenberger: Complete Works | https://en.wikipedia.org/wiki/Marcel-Paul_Schützenberger |
The Marcel Benoist Prize , offered by the Marcel Benoist Foundation , is a monetary prize that has been offered annually since 1920 to a scientist of Swiss nationality or residency who has made the most useful scientific discovery. Emphasis is placed on those discoveries affecting human life. Since 1997, candidates in the humanities have also been eligible for the prize.
The Marcel Benoist Foundation was established by the will of the French lawyer Marcel Benoist, a wartime resident of Lausanne , who died in 1918. It is managed by a group of trustees comprising the Swiss interior minister and heads of the main Swiss universities . It has been dubbed the "Swiss Nobel Prize." [ 1 ]
The first award was given to immunologist Maurice Arthus (1862–1945) at the University of Lausanne . Other winners have included computer scientist Niklaus Wirth , astronomer Michel Mayor , and cardiologist Max Holzmann . As of 2019 [update] , eleven Marcel Benoist winners have later also won the Nobel Prize : Paul Karrer, Leopold Ruzicka, Walter R. Hess, Tadeus Reichstein, Vladimir Prelog, Niels Kaj Jerne, Johannes G. Bednorz, Karl. Alexander Müller, Richard R. Ernst, Kurz Wüthrich, and Michel Mayor.
In 2009, Françoise Gisou van der Goot ( École polytechnique fédérale de Lausanne ) was the first woman to win the Marcel Benoist Prize.
This science awards article is a stub . You can help Wikipedia by expanding it .
This Switzerland -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Marcel_Benoist_Prize |
Marcel Grossmann ( Hungarian : Grossmann Marcell ; April 9, 1878 – September 7, 1936) [ 2 ] was a Swiss mathematician who was a friend and classmate of Albert Einstein . Grossmann came from an old Swiss family in Zürich . His father managed a textile factory. He became a Professor of Mathematics at the Federal Polytechnic School in Zürich, today the ETH Zurich , specializing in descriptive geometry .
In 1900 Grossmann graduated from the Federal Polytechnic School (ETH) and became an assistant to the geometer Wilhelm Fiedler . [ 3 ] He continued to do research on non-Euclidean geometry and taught in high schools for the next seven years. In 1902, he earned his doctorate from the University of Zurich with the thesis Ueber die metrischen Eigenschaften kollinearer Gebilde (translated On the Metrical Properties of Collinear Structures ) with Fiedler as advisor. In 1907, he was appointed full professor of descriptive geometry at the Federal Polytechnic School. [ 4 ]
As a professor of geometry, Grossmann organized summer courses for high school teachers. In 1910, he became one of the founders of the Swiss Mathematical Society . He was an Invited Speaker of the ICM in 1912 at Cambridge [ 5 ] and in 1920 at Strasbourg .
Albert Einstein 's friendship with Grossmann began with their school days in Zürich. Grossmann's careful and complete lecture notes at the Federal Polytechnic School proved to be a salvation for Einstein, who missed many lectures. [ 6 ] Grossmann's father helped Einstein get his job at the Swiss Patent Office in Bern , [ 7 ] and it was Grossmann who helped to conduct the negotiations to bring Einstein back from Prague as a professor of physics at the Zurich Polytechnic. Grossmann was an expert in differential geometry and tensor calculus ; just the mathematical tools providing a proper mathematical framework for Einstein's work on gravity. Thus, it was natural that Einstein would enter into a scientific collaboration with Grossmann. [ 8 ]
It was Grossmann who emphasized the importance of a non-Euclidean geometry called Riemannian geometry (also elliptic geometry ) to Einstein, which was a necessary step in the development of Einstein's general theory of relativity . Abraham Pais 's book [ 9 ] on Einstein suggests that Grossmann mentored Einstein in tensor theory as well. Grossmann introduced Einstein to the absolute differential calculus , started by Elwin Bruno Christoffel [ 10 ] and fully developed by Gregorio Ricci-Curbastro and Tullio Levi-Civita . [ 11 ] Grossmann facilitated Einstein's unique synthesis of mathematical and theoretical physics in what is still today considered the most elegant and powerful theory of gravity: the general theory of relativity. The collaboration of Einstein and Grossmann led to a ground-breaking paper, "Outline of a Generalized Theory of Relativity and of a Theory of Gravitation", which was published in 1913 and was one of the two fundamental papers which established Einstein's theory of gravity. [ 12 ]
Grossmann died of multiple sclerosis in 1936. [ 13 ] The community of relativists celebrates Grossmann's contributions to physics by organizing Marcel Grossmann meetings every three years.
The International Center for Relativistic Astrophysics presents the Marcel Grossmann Awards . Each recipient receives a silver casting of the T. E. S. T. sculpture [ 14 ] by the artist A. Pierelli. Each year, an institution is selected and between two and six individual scientists are selected. Past institutional winners include the Planck Scientific Collaboration ( ESA ), AlbaNova University Center, Institut des Hautes Etudes Scientifique ( IHES ) and others. Past individual winners include Shing-Tung Yau , Tsung-Dao Lee , Christine Jones Forman and Stephen Hawking . | https://en.wikipedia.org/wiki/Marcel_Grossmann |
Marcel Kuntz is a French plant biotechnologist who is a Research Director in the Laboratoire de Physiologie Cellulaire Végétale (Laboratory of Plant and Cell Physiology) at the Centre National de la Recherche Scientifique (National Centre for Scientific Research) in Grenoble , France . He is known for his criticisms of the ways that the French government and popular media have exaggerated the risks associated with genetically modified foods . He has documented how public perception of the risks of such foods has diverged significantly from the conclusions that scientists have reached on the topic. [ 1 ] [ 2 ] He was a recipient of the Médaille d'Or (Gold Medal) from the Académie d'Agriculture (French Academy of Agriculture) in 2017. [ 3 ]
This article about a French biologist is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Marcel_Kuntz |
Marcel Joseph Vogel (April 14, 1917 – February 12, 1991) was a research scientist working at the IBM San Jose Research Center for 27 years. He is sometimes referred to as Dr. Vogel, although this title was based on an honorary degree , not a Ph.D. Later in his career, he became interested in various theories of quartz crystals and other occult and esoteric fields of study.
It is claimed that Vogel started his research into luminescence while he was still in his teens. This research eventually led him to publish his thesis, Luminescence in Liquids and Solids and Their Practical Application , in collaboration with University of Chicago 's Dr. Peter Pringsheim in 1943.
Two years after the publication, Vogel incorporated his own company, Vogel Luminescence, in San Francisco . For the next decade the firm developed a variety of new products: fluorescent crayons , tags for insecticides , a black light inspection kit to determine the secret trackways of rodents in cellars from their urine and the psychedelic colors popular in " new age " posters. In 1957, Vogel Luminescence was sold to Ultra Violet Products and Vogel joined IBM as a full-time research scientist. He retired from IBM in 1984.
In 1977 and 1978, Vogel participated in experiments with the Markovich Tesla Electrical Power Source, referred to as MTEPS, that was built by Peter T. Markovich. [ 1 ]
He received 32 patents for his inventions up through his tenure at IBM. [ 2 ] Among these was the magnetic coating for the 24" hard disk drive systems still in use. His areas of expertise, besides luminescence, were phosphor technology, magnetics and liquid crystal systems.
At Vogel's February 14, 1991 funeral, IBM researcher and Sacramento, California physician Bernard McGinity, M.D. said of him, "He made his mark because of the brilliance of his mind, his prolific ideas, and his seemingly limitless creativity." [ 3 ]
Vogel was a proponent of crystal healing , and believed cut crystals can have healing powers. [ 4 ]
Vogel examined a metal sample which was allegedly given to Billy Meier by extraterrestrials , but by misinterpreting a graph on a test instrument, erroneously concluded it contained thallium , a rare metal. [ 5 ]
Vogel was a proponent of research into plant consciousness and believed "empathy between plant and human" could be established. [ 6 ]
Vogel was featured in the first episode of In Search Of... hosted by Leonard Nimoy , called "Other Voices". He gave his theories regarding the possibility of communication between plants . [ citation needed ] | https://en.wikipedia.org/wiki/Marcel_Vogel |
In mathematical physics , more specifically the one-dimensional inverse scattering problem , the Marchenko equation (or Gelfand-Levitan-Marchenko equation or GLM equation ), named after Israel Gelfand , Boris Levitan and Vladimir Marchenko , is derived by computing the Fourier transform of the scattering relation:
Where g ( r , r ′ ) {\displaystyle g(r,r^{\prime })\,} is a symmetric kernel , such that g ( r , r ′ ) = g ( r ′ , r ) , {\displaystyle g(r,r^{\prime })=g(r^{\prime },r),\,} which is computed from the scattering data. Solving the Marchenko equation, one obtains the kernel of the transformation operator K ( r , r ′ ) {\displaystyle K(r,r^{\prime })} from which the potential can be read off. This equation is derived from the Gelfand–Levitan integral equation , using the Povzner–Levitan representation .
Suppose that for a potential u ( x ) {\displaystyle u(x)} for the Schrödinger operator L = − d 2 d x 2 + u ( x ) {\displaystyle L=-{\frac {d^{2}}{dx^{2}}}+u(x)} , one has the scattering data ( r ( k ) , { χ 1 , ⋯ , χ N } ) {\displaystyle (r(k),\{\chi _{1},\cdots ,\chi _{N}\})} , where r ( k ) {\displaystyle r(k)} are the reflection coefficients from continuous scattering, given as a function r : R → C {\displaystyle r:\mathbb {R} \rightarrow \mathbb {C} } , and the real parameters χ 1 , ⋯ , χ N > 0 {\displaystyle \chi _{1},\cdots ,\chi _{N}>0} are from the discrete bound spectrum. [ 1 ]
Then defining F ( x ) = ∑ n = 1 N β n e − χ n x + 1 2 π ∫ R r ( k ) e i k x d k , {\displaystyle F(x)=\sum _{n=1}^{N}\beta _{n}e^{-\chi _{n}x}+{\frac {1}{2\pi }}\int _{\mathbb {R} }r(k)e^{ikx}dk,} where the β n {\displaystyle \beta _{n}} are non-zero constants, solving the GLM equation K ( x , y ) + F ( x + y ) + ∫ x ∞ K ( x , z ) F ( z + y ) d z = 0 {\displaystyle K(x,y)+F(x+y)+\int _{x}^{\infty }K(x,z)F(z+y)dz=0} for K {\displaystyle K} allows the potential to be recovered using the formula u ( x ) = − 2 d d x K ( x , x ) . {\displaystyle u(x)=-2{\frac {d}{dx}}K(x,x).}
This scattering –related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Marchenko_equation |
Marchetti dilatometer test or flat dilatometer , is a type of dilatometer commonly designated by DMT.
It was created by Silvano Marchetti (1980) and is one of the most versatile tools for soil characterization, namely loose to medium compacted granular soils and soft to medium clays, or even stiffer if a good reaction system is provided. The main reasons for its usefulness deriving geotechnical parameters are related to the simplicity and the speed of execution, generating continuous data profiles of high accuracy and reproducibility. [ 1 ] | https://en.wikipedia.org/wiki/Marchetti_dilatometer_test |
The marching ants effect is an animation technique often found in selection tools of computer graphics programs. It helps the user to distinguish the selection border from the image background by animating the border. The border is a dotted or dashed line where the dashes seem to move slowly sideways and up and down. This creates an illusion of ants marching in line as the black and white parts of the line start to move. Some prefer the term marquee selection, as the effect resembles the chaser lights of a marquee , and this term can be considered a synonym. Popular graphics programs, such as the GIMP and Adobe Photoshop , implement their selection tools using the marching ants effect. The technique was first widely used by the MacPaint program developed by Bill Atkinson .
The easiest way to achieve this animation is by drawing the selection using a pen pattern that contains diagonal lines. If the selection outline is only one pixel thick, the slices out of the pattern will then look like a dashed line, and the animation can easily be achieved by simply shifting the pattern one pixel sideways and redrawing the outline. The method has the disadvantage of not looking like marching ants with selection borders that are not parallel to the coordinate axes.
With the selection problem in mind, Bill Atkinson went to his favorite pub in Los Gatos , California. Something on the wall caught his attention. It was an electric Hamm's Beer sign. The beer sign consisted of an illuminated scene of a kind of animated waterfall. Water seemed to flow down the waterfall into the lake. Bill figured that this effect could solve his problem because it is easily recognizable.
He implemented the idea and showed it to Rod Perkins from the Lisa team, who told Bill the effect reminded him of "marching ants". [ 1 ] | https://en.wikipedia.org/wiki/Marching_ants |
The Marchywka effect [ 2 ] [ 3 ] refers to electrochemical cleaning of diamond using an electric field induced with remote electrodes.
It was first observed by accident by Mike Marchywka [ 1 ] while trying to find a selective means to etch non-diamond carbon and fabricate simple astronomical UV detection devices. [ 4 ] These devices required a few specific features such as clean surfaces and patterned areas of non-diamond carbon but the approach has subsequently been explored as a more general means to terminate carbon surfaces and selectively clean and etch various other materials or structures. The term "Marchywka effect" is not used consistently and sometimes the term "bipolar surface treatment" is used [ 5 ] as the substrate is induced to become a bipolar electrode . [ 6 ] Various phrases such as "non-contacted electrochemical" process may also be used (see any references cited herein) or it may be mentioned as just an "electrochemical etch". [ 7 ] [ 8 ]
While this is easily confused with various common electrochemical cells, and may appear to be a trivial and obvious extension of well known methods, recent patents [ 9 ] continue to reference prior work [ 10 ] that cites non-contactedness as a feature. The use of a low conductivity medium as used in Marchywka et al.'s original paper [ 4 ] is sometimes noted when it is used and may produce new effects. [ 11 ] [ 12 ] The apparatus to create the effect is similar to the well-known electroporation system except that the biological specimen is replaced with an inorganic substrate, [ 4 ] although, in some cases, organic films can be etched with this process using a surfactant solution as the electrolyte .
As a "non-contact" process, the effect differs from traditional electrochemical processes where carrier flow through the surface is achieved by connection to a current source with highly conductive materials such as copper wire. Materials contacted to an anode can be modified in a variety of ways including anodizing and electropolishing . Electrochemistry was quickly recognized as an important related field in the popular press once the first synthetic diamonds were made. [ 14 ] However, the use of an induced field created by remote electrodes allows discontinuous areas on an insulating substrate to be cleaned, modified, or etched (similar to electroetching ), greatly expanding the role of electrochemical methods.
The mechanism is presumed to be due to the induced field but little in the way of exhaustive analysis has been done, as the actual processes do not appear to differ from traditional approaches. For example, "identified as the ‘Marchywka Effect’ in the literature. The etching may be due to the galvanic coupling of diamond and non-diamond carbon". [ 15 ] The applied field apparently creates directed surface modifications on polished diamond surfaces with little or no actual removal of material. This may be desirable for making various devices, or simply studying the properties of the diamond surface. The induced field deposits or replaces a single layer of some molecule and this could be thought of as a monolayer electroplating method. It has been elucidated in more fully in many works. [ 16 ] [ 17 ]
Many prior technologies exist for preparing wide-gap diamond for use in electronic devices or as a substrate for single-crystal diamond growth. The more stable forms of carbon have lower gaps and different crystal structures, and their presence must be carefully controlled. The Marchywka Effect has been characterised and compared to alternative means to create a desired surface for several applications.
Removal of non-diamond carbon with wet chemicals had been accomplished by boiling in mixtures of sulfuric and chromic acid . When applied to a diamond substrate with an ion implantation damage profile as may be used for basic science, crystal growth, or device fabrication, [ 18 ] [ 19 ] the electrochemical approach makes it easier to preserve the thin film of less damaged diamond lying above the implant range, and it has been used in annealing experiments to fix the diamond after implantation damage has occurred. [ 20 ] In some cases, thermal cycling may be an issue and selectivity to various masks may be important, so the lower temperatures and more flexible chemistry may offer benefits over prior art.
The method does not require the use of non-volatile materials [ citation needed ] such as chrome, possibly reducing contamination problems in some applications. The ability to control the etching direction and speed with an applied voltage or electrode configuration, as with electrochemical machining , gives additional capabilities not available with isotropic chemical-only approaches. Dry processing methods such as hot oxygen or plasmas can also burn off the graphite faster than the diamond, as can a simple acetylene torch . These require higher temperatures and do not have the same high selectivity that can be achieved with the electrochemical approach. [ 21 ]
Surface termination is often an issue with both solid state and vacuum devices, and the details of final surface band structure have been compared with alternatives in various device structures. [ 22 ] [ 23 ]
While the original effort failed to produce useful products, follow-on work in Europe did produce usable astronomical detectors [ 24 ] [ 25 ] but without apparent use of this technology. In other areas, however, the approach seems to be competitive, with prior art for making various end-products, since it has been used as a fabrication step for experimental devices and structures. Many groups have used the approach to grow homoepitaxial diamond [ citation needed ] and subsequently release the thin-films with a variety of "lift-off" processes. [ 26 ]
It has also been considered in contexts such as carbon microelectromechanical systems production [ 27 ] [ 28 ] and different materials applications, for example with non-contacted palladium [ 6 ] [ 29 ] deposition and extensions. [ 9 ] While not citing Marchywka et al.'s original paper, these continue to cite non-contactedness as a feature,
"The electrode assembly and the conductive surface may be positioned in close proximity to, but without contacting, one another". [ 9 ] references a much earlier patent [ 10 ] covering related attempts to achieve non-contacted electro-etching, "The present invention relates to a method of and apparatus for electrochemically processing metallic surfaces of workpieces arranged in a contact-free manner with regard to the cathode and anode[...]." [ 4 ]
The effect has been mentioned in passing with regard to novel devices such
as quantum coherent devices [ 30 ] while patents on emerging uses for amorphous carbon [ 31 ] [ 32 ] and
diamond thermal conductors [ 33 ] by manufacturers of high density electronic chips reference the related lift-off technology. | https://en.wikipedia.org/wiki/Marchywka_effect |
RWTH Aachen University
H. Lee Moffitt Cancer Center & Research Institute
Marcin Kortylewski is a Polish American cancer researcher and immunologist . He is currently professor of immuno-oncology at the Beckman Research Institute of the City of Hope National Medical Center in Duarte, California . [ 1 ] His research has shown that the STAT3 protein plays a role in protecting cancers from immune responses and contributes to resistance to therapies. [ 2 ] [ 3 ] Later he developed a two-pronged strategy for cancer immunotherapy using simultaneous STAT3 inhibition and TLR9 immune stimulation. [ 4 ] [ 5 ] [ 6 ] Kortylewski invented platform strategy for delivery of oligonucleotides , such as siRNA , [ 7 ] miRNA , [ 8 ] decoy DNA, [ 6 ] [ 9 ] antisense molecules [ 10 ] and others to selected immune cells.
Kortylewski was born in Poznań, Poland . He received his M.S. in biotechnology from Adam Mickiewicz University and his Ph.D. in molecular biology from the Poznań University of Medical Sciences in Poznań, Poland. [ 1 ] [ 11 ] Dr. Kortylewski completed postdoctoral training in cancer biology in Institute of Biochemistry at RWTH Aachen in Germany and later in tumor immunology at H. Lee Moffitt Cancer Center in Tampa, Florida in USA. [ 1 ]
Kortylewski began his post-graduate career in 1999 as a postdoctoral fellow in Iris Behrman’s lab in RWTH Aachen /Institute of Biochemistry chaired by Peter C. Heinrich. During his tenure there, he co-authored numerous research articles. [ 12 ] Later, he moved to H. Lee Moffitt Cancer Center in Tampa, Florida in USA to train with Richard Jove and Hua Yu. In 2005, he became Assistant Research Professor in the Beckman Research Institute of the City of Hope National Medical Center in Duarte, California . There, he became tenured faculty in 2010 and full professor at the Department of Immuno-Oncology in 2021. [ citation needed ]
Kortylewski's research group focuses on understanding the mechanisms by which cancers evade the immune system and explores methods to enhance antitumor immune responses using DNA and RNA-based drugs. [ 1 ] [ 13 ] [ 14 ] In early 2000s, he demonstrated that tumors turn off immune cell activity using a transcription factor, STAT3. [ 3 ] His studies characterized STAT3 as a multitasking protein which prevents immune activation, while stimulating tumor vascularization and metastasis. [ 5 ] [ 2 ] Kortylewski invented a two-pronged strategy for cancer immunotherapy combining STAT3 blocking using siRNA with triggering of immune receptor, Toll-like receptor 9 ( TLR9 ) using CpG motif DNA. [ 15 ] [ 7 ] [ 16 ] Later on, he adopted the strategy as a platform for delivery of various oligonucleotide drugs to target oncogenic or immune regulators, such as STAT3, NF-kB or selected miRNAs [ 17 ] [ 18 ] [ 19 ] in human or mouse immune cells in vivo.
Kortylewski is a co-founder of a biomedical startup company, currently under the name Duet Biotherapeutics Inc., focused on advancing CpG-STAT3 inhibitors to clinical trials for cancer immunotherapy. [ 20 ] [ 21 ] He is an active contributor to the field of immune-oncology and oligonucleotide therapeutics, serving on scientific and editorial boards of journals and various organizations. [ 22 ] [ 23 ] [ 24 ]
In 2016, Kortylewski was a recipient of an Outstanding Young Investigator Award from American Society of Gene and Cell Therapy , granted based on the contributions to the field of gene and cell therapy. [ 25 ] He received the award specifically for his work on “Eliminating Tumor Immune Defenses using Oligonucleotide Therapeutics”.
US 10,253,318
US 10,829,765
US 11,186,840
CTLA-4 Aptamer Conjugates | https://en.wikipedia.org/wiki/Marcin_Kortylewski |
In mathematics , the Marcinkiewicz–Zygmund inequality , named after Józef Marcinkiewicz and Antoni Zygmund , gives relations between moments of a collection of independent random variables . It is a generalization of the rule for the sum of variances of independent random variables to moments of arbitrary order. It is a special case of the Burkholder-Davis-Gundy inequality in the case of discrete-time martingales.
Theorem [ 1 ] [ 2 ] If X i {\displaystyle \textstyle X_{i}} , i = 1 , … , n {\displaystyle \textstyle i=1,\ldots ,n} , are independent random variables such that E ( X i ) = 0 {\displaystyle \textstyle E\left(X_{i}\right)=0} and E ( | X i | p ) < + ∞ {\displaystyle \textstyle E\left(\left\vert X_{i}\right\vert ^{p}\right)<+\infty } , 1 ≤ p < + ∞ {\displaystyle \textstyle 1\leq p<+\infty } , then
where A p {\displaystyle \textstyle A_{p}} and B p {\displaystyle \textstyle B_{p}} are positive constants, which depend only on p {\displaystyle \textstyle p} and not on the underlying distribution of the random variables involved.
In the case p = 2 {\displaystyle \textstyle p=2} , the inequality holds with A 2 = B 2 = 1 {\displaystyle \textstyle A_{2}=B_{2}=1} , and it reduces to the rule for the sum of variances of independent random variables with zero mean, known from elementary statistics: If E ( X i ) = 0 {\displaystyle \textstyle E\left(X_{i}\right)=0} and E ( | X i | 2 ) < + ∞ {\displaystyle \textstyle E\left(\left\vert X_{i}\right\vert ^{2}\right)<+\infty } , then
Several similar moment inequalities are known as Khintchine inequality and Rosenthal inequalities , and there are also extensions to more general symmetric statistics of independent random variables. [ 3 ] | https://en.wikipedia.org/wiki/Marcinkiewicz–Zygmund_inequality |
Marco Wilhelmus Fraaije (born 7 December 1968) is a Dutch scientist whose research concerns enzymology of redox enzymes, enzyme discovery & engineering and biocatalysis at the Groningen Biomolecular Sciences and Biotechnology Institute (GBB) at the University of Groningen . [ 1 ] [ 2 ] [ 3 ] [ 4 ]
Marco Fraaije graduated in 1993 with a Master of Science degree in Molecular Sciences at Wageningen University . [ 5 ] Subsequently, he became a doctoral student at Wageningen University under supervision of Willem van Berkel focusing on the mechanism and structure of flavoenzymes and was awarded his PhD in biochemistry in 1998. [ 6 ] Following his PhD, he worked as a postdoctoral researcher as EMBO fellow in the protein crystallography research group at the University of Pavia . In 1999, he was made assistant professor at GBB at the University of Groningen , and in 2007 he was appointed as associate professor. In 2012, he was made full professor in molecular enzymology. [ 5 ]
Fraaije is active in the fields of enzyme engineering and biocatalysis . [ 1 ] His research mainly deals with discovery, engineering and exploration of novel oxidative enzymes , with special emphasis on flavin-containing enzymes . [ 7 ] Besides exploring the biocatalytic potential of these biocatalysts, he also aims at elucidating the molecular functioning of oxidative flavoenzymes. [ 2 ] He also has interest in evolutionary aspects of enzymology and in line with this he is board member of the geological museum Oertijdmuseum in Boxtel . [ 8 ]
Marco Fraaije has a significant number of publications and four patents. [ 1 ] [ 9 ] He has coordinated EU-funded projects including OXYGREEN (2008-2013), [ 10 ] ROBOX (2015-2019), [ 11 ] and OXYTRAIN (2017-2020). [ 12 ]
In 2018, Fraaije received the BIOCAT science award from the Biocat Society at the International Congress on Biocatalysis for his scientific achievement in the field of biocatalysis. [ 13 ] Other research prizes include the Unilever research prize, 1993; EMBO long-term fellowship, 1998; and the VICI-NWO research grant, 2016. [ 5 ]
In 2005, he became a member of the Biomolecular Chemistry division of the Netherlands Organization for Scientific Research and currently chairs the Applied Biocatalysis division of the Dutch Biotechnology Society. [ 14 ] | https://en.wikipedia.org/wiki/Marco_Fraaije |
Distinguished Scientist, BC Cancer Research Institute, BC Cancer
Marco Antonio Marra is a distinguished scientist and director of Canada's Michael Smith Genome Sciences Centre at the BC Cancer Research Centre and professor of medical genetics at the University of British Columbia (UBC). He also serves as UBC Canada Research Chair in Genome Science for the Canadian Institutes of Health Research and is an inductee in the Canadian Medical Hall of Fame .
Canadian born and educated, Marco Marra received a B.Sc. in molecular & cell biology and a PhD in genetics from Simon Fraser University. The title of his PhD thesis : “Genome analysis in Caenorhabditis elegans : Genetic and molecular identification of genes tightly linked to unc-22(IV)” . [ 1 ]
Marra trained as a post-doctoral fellow at the Washington University School of Medicine in St Louis , Missouri. He went on to become Group Leader of both the EST (Express Sequence Tag) Sequencing Team and Genome Fingerprinting and Mapping Teams at Washington University in St. Louis ’s Genome Sequence Center (renamed the McDonnell Genome Institute ). [ 2 ]
During his first two years with British Columbia’s Genome Sequence Center (renamed Canada's Michael Smith Genome Sciences Centre), Marra served as head of the mapping and sequencing teams, associate director and Scientific Co-Director. He also held the position of senior scientist at BC Cancer Research and adjunct professor for the Department of Medical Genetics. Marra subsequently became professor and head of the Department of Medical Genetics in the Faculty of Medicine at UBC.
From 2011 to 2018, Marra founded and co-directed the Genome Science and Technology Graduate Program at UBC. He also served as adjunct professor at the Department of Molecular Biology and Biochemistry at Simon Fraser University from 2001 to 2015. Marra took over as director of Canada's Michael Smith Genome Sciences Centre (GSC) when Dr. Smith died of cancer in 2000.
Along with GSC co-director, Dr. Steven J.M. Jones, Marra was instrumental in creating the first map the human genome , an international initiative that allowed the data to remain in the public domain.
The paper published in the 15 February 2001 issue of Nature, titled "A physical map of the human genome", [ 3 ] describes the construction and use of the human genome map to fuel human genome sequencing. Marra made fundamental contributions to that effort by devising and then implementing clonal fingerprinting [ 4 ] techniques that led to the construction and use of the map, which served as the centralized coordinating resource for the sequencing effort.
Led by Marra, the GSC was first in the world to sequence the SARS virus [ 5 ] in 2003. Using this information they were the first to identify SARS as a coronavirus . This discovery, along with knowledge of the SARS genome, had significant implications for many infectious diseases and vaccine development. Sequencing techniques used for SARs were also applied to many fields of research and discovery, including cancer.
In 2020, the GSC joined the Canadian COVID Genomics Network (CanCOGeN), a Genome Canada initiative to generate accessible and usable genomics data to inform COVID-19 public health decisions. The GSC was one of the first three facilities involved in sequencing 10,000 Canadians that tested positive for the virus (HostSeq) for this Government of Canada funded project. Research co-led by Marra also identified an alternative procedure for extracting nucleic acids for COVID-19 testing. [ 6 ]
As part of a GSC initiative, Marra played a pivotal role in the first proof-of-concept [ 7 ] for the effective use of whole genome analyses in personalized cancer medicine, leading to the development of BC Cancer’s Personalized OncoGenomics (POG) program. POG, co-led by Dr. Janessa Laskin, represents one of the first applications of whole genome sequencing in a clinical setting, using information derived from thousands of individual cancer genomes and transcriptomes to identify promising therapeutic targets in individual patients.
In 2019, Marra and the POG team became a key part of the Marathon of Hope Cancer Centres Network. Led by the Terry Fox Research Institute and the Terry Fox Foundation , with support from dozens of research and funding partners across Canada, this represents the country’s largest ever clinical data-sharing initiative. The Marathon of Hope aims to accelerate the adoption of precision medicine for cancer patients throughout Canada.
Marra continues to extend the reach of genomics toward managing and eradicating disease. His research has uncovered new cancer mutations, candidate biomarkers and therapeutic targets, and has been instrumental in demonstrating the functional interplay between the cancer genome and epigenome.
Marra's contributions to genome science led to an honorary Doctor of Science degree from Simon Fraser University in 2004, and an honorary Doctor of Laws degree from the University of Calgary in 2005. He is also a recipient of the Order of British Columbia [ 8 ] and became a member of the Canadian Medical Hall of Fame in 2020. [ 9 ]
In 2024, he was appointed as an officer to the Order of Canada . [ 10 ] He lives in Vancouver . [ 11 ] | https://en.wikipedia.org/wiki/Marco_Marra |
In theoretical chemistry , Marcus theory is a theory originally developed by Rudolph A. Marcus , starting in 1956, to explain the rates of electron transfer reactions – the rate at which an electron can move or jump from one chemical species (called the electron donor ) to another (called the electron acceptor ). [ 1 ] It was originally formulated to address outer sphere electron transfer reactions, in which the two chemical species only change in their charge with an electron jumping (e.g. the oxidation of an ion like Fe 2+ /Fe 3+ ), but do not undergo large structural changes. It was extended to include inner sphere electron transfer contributions, in which a change of distances or geometry in the solvation or coordination shells of the two chemical species is taken into account (the Fe-O distances in Fe(H 2 O) 2+ and Fe(H 2 O) 3+ are different). [ 2 ] [ 3 ]
For electron transfer reactions without making or breaking bonds Marcus theory takes the place of Eyring's transition state theory [ 4 ] [ 5 ] which has been derived for reactions with structural changes. Both theories lead to rate equations of the same exponential form. However, whereas in Eyring theory the reaction partners become strongly coupled in the course of the reaction to form a structurally defined activated complex, in Marcus theory they are weakly coupled and retain their individuality. It is the thermally induced reorganization of the surroundings, the solvent (outer sphere) and the solvent sheath or the ligands (inner sphere) which create the geometrically favourable situation prior to and independent of the electron jump.
The original classical Marcus theory for outer sphere electron transfer reactions demonstrates the importance of the solvent and leads the way to the calculation of the Gibbs free energy of activation, using the polarization properties of the solvent, the size of the reactants, the transfer distance and the Gibbs free energy Δ G ∘ {\displaystyle \Delta G^{\circ }} of the redox reaction. The most startling result of Marcus' theory was the "inverted region": whereas the reaction rates usually become higher with increasing exergonicity of the reaction, electron transfer should, according to Marcus theory, become slower in the very negative Δ G ∘ {\displaystyle \Delta G^{\circ }} domain. Scientists searched the inverted region for proof of a slower electron transfer rate for 30 years until it was unequivocally verified experimentally in 1984. [ 6 ]
R. A. Marcus received the Nobel Prize in Chemistry in 1992 for this theory. Marcus theory is used to describe a number of important processes in chemistry and biology, including photosynthesis , corrosion , certain types of chemiluminescence , charge separation in some types of solar cells and more. Besides the inner and outer sphere applications, Marcus theory has been extended to address heterogeneous electron transfer .
In a redox reaction an electron donor D must diffuse to the acceptor A, forming a precursor complex, which is labile but allows electron transfer to give successor complex. The pair then dissociates. For a one electron transfer the reaction is
(D and A may already carry charges). Here k 12 , k 21 and k 30 are diffusion constants, k 23 and k 32 are rate constants of activated reactions. The total reaction may be diffusion controlled (the electron transfer step is faster than diffusion, every encounter leads to reaction) or activation controlled (the "equilibrium of association" is reached, the electron transfer step is slow, the separation of the successor complex is fast). The ligand shells around A and D are retained. This process is called outer sphere electron transfer . Outer sphere ET is the main focus of traditional Marcus Theory. The other kind or redox reactions is inner sphere where A and D are covalently linked by a bridging ligand . Rates for such ET reactions depend on ligand exchange rates.
In outer sphere redox reactions no bonds are formed or broken; only an electron transfer (ET) takes place. A quite simple example is the Fe 2+ /Fe 3+ redox reaction, the self exchange reaction which is known to be always occurring in an aqueous solution containing the aquo complexes [Fe(H 2 O) 6 ] 2+ and [Fe(H 2 O)6] 3+ . Redox occurs with Gibbs free reaction energy Δ G ∘ = 0 {\displaystyle \Delta G^{\circ }=0} .
From the reaction rate's temperature dependence an activation energy is determined, and this activation energy is interpreted as the energy of the transition state in a reaction diagram. The latter is drawn, according to Arrhenius and Eyring, as an energy diagram with the reaction coordinate as the abscissa. The reaction coordinate describes the minimum energy path from the reactants to the products, and the points of this coordinate are combinations of distances and angles between and in the reactants in the course of the formation and/or cleavage of bonds. The maximum of the energy diagram, the transition state , is characterized by a specific configuration of the atoms. Moreover, in Eyring's TST [ 4 ] [ 5 ] a quite specific change of the nuclear coordinates is responsible for crossing the maximum point, a vibration in this direction is consequently treated as a translation.
For outer sphere redox reactions there cannot be such a reaction path, but nevertheless one does observe an activation energy. The rate equation for activation-controlled reactions has the same exponential form as the Eyring equation,
Δ G ‡ {\displaystyle \Delta G^{\ddagger }} is the Gibbs free energy of the formation of the transition state, the exponential term represents the probability of its formation, A contains the probability of crossing from precursor to successor complex.
The consequence of an electron transfer is the rearrangement of charges, and this greatly influences the solvent environment. For the dipolar solvent molecules rearrange in the direction of the field of the charges (this is called orientation polarisation), and also the atoms and electrons in the solvent molecules are slightly displaced (atomic and electron polarization, respectively). It is this solvent polarization which determines the free energy of activation and thus the reaction rate.
Substitution, elimination and isomerization reactions differ from the outer sphere redox reaction not only in the structural changes outlined above, but also in the fact that the movements of the nuclei and the shift of charges ( charge transfer , CT) on the reactions path take place in a continuous and concerted way: nuclear configurations and charge distribution are always "in equilibrium". This is illustrated by the S N 2 substitution of the saponification of an alkyl halide where the rear side attack of the OH − ion pushes out a halide ion and where a transition state with a five-coordinated carbon atom must be visualized. The system of the reactants becomes coupled so tightly during the reaction that they form the activated complex as an integral entity. The solvent here has a minor effect.
By contrast, in outer sphere redox reactions the displacement of nuclei in the reactants are small, here the solvent has the dominant role. Donor-acceptor coupling is weak, both keep their identity during the reaction. Therefore, the electron, being an elementary particle, can only "jump" as a whole ( electron transfer , ET). If the electron jumps, the transfer is much faster than the movement of the large solvent molecules, with the consequence that the nuclear positions of the reaction partners and the solvent molecules are the same before and after the electron jump ( Franck–Condon principle ). [ 7 ] The jump of the electron is governed by quantum mechanical rules, it is only possible if also the energy of the ET system does not change "during" the jump.
The arrangement of solvent molecules depends on the charge distribution on the reactants. If the solvent configuration must be the same before and after the jump and the energy may not change, then the solvent cannot be in the solvation state of the precursor nor in that of the successor complex as they are different, it has to be somewhere in between. For the self-exchange reaction for symmetry reasons an arrangement of the solvent molecules exactly in the middle of those of precursor and successor complex would meet the conditions. This means that the solvent arrangement with half of the electron on both donor and acceptor would be the correct environment for jumping. Also, in this state the energy of precursor and successor in their solvent environment would be the same.
However, the electron as an elementary particle cannot be divided, it resides either on the donor or the acceptor and arranges the solvent molecules accordingly in an equilibrium. The "transition state", on the other hand, requires a solvent configuration which would result from the transfer of half an electron, which is impossible. This means that real charge distribution and required solvent polarization are not in an "equilibrium". Yet it is possible that the solvent takes a configuration corresponding to the "transition state", even if the electron sits on the donor or acceptor. This, however, requires energy. This energy may be provided by the thermal energy of the solvent and thermal fluctuations can produce the correct polarization state. Once this has been reached the electron can jump. The creation of the correct solvent arrangement and the electron jump are decoupled and do not happen in a synchronous process. Thus the energy of the transition state is mostly polarization energy of the solvent.
On the basis of his reasoning R.A. Marcus developed a classical theory with the aim of calculating the polarization energy of the said non-equilibrium state. From thermodynamics it is well known that the energy of such a state can be determined if a reversible path to that state is found. Marcus was successful in finding such a path via two reversible charging steps for the preparation of the "transition state" from the precursor complex.
Four elements are essential for the model on which the theory is based:
Marcus' tool is the theory of dielectric polarization in solvents. He solved the problem in a general way for a transfer of charge between two bodies of arbitrary shape with arbitrary surface and volume charge. For the self-exchange reaction, the redox pair (e.g. Fe(H 2 O) 6 3+ / Fe(H 2 O) 6 2+ ) is substituted by two macroscopic conducting spheres at a defined distance carrying specified charges. Between these spheres a certain amount of charge is reversibly exchanged.
In the first step the energy W I of the transfer of a specific amount of charge is calculated, e.g. for the system in a state when both spheres carry half of the amount of charge which is to be transferred. This state of the system can be reached by transferring the respective charge from the donor sphere to the vacuum and then back to the acceptor sphere. [ 8 ] Then the spheres in this state of charge give rise to a defined electric field in the solvent which creates the total solvent polarization P u + P e . By the same token this polarization of the solvent interacts with the charges.
In a second step the energy W II of the reversible (back) transfer of the charge to the first sphere, again via the vacuum, is calculated. However, the atom and orientation polarization P u is kept fixed , only the electron polarization P e may adjust to the field of the new charge distribution and the fixed P u . After this second step the system is in the desired state with an electron polarization corresponding to the starting point of the redox reaction and an atom and orientation polarization corresponding to the "transition state". The energy W I + W II of this state is, thermodynamically speaking, a Gibbs free energy G.
Of course, in this classical model the transfer of any arbitrary amount of charge Δe is possible. So the energy of the non-equilibrium state, and consequently of the polarization energy of the solvent, can be probed as a function of Δe. Thus Marcus has lumped together, in a very elegant way, the coordinates of all solvent molecules into a single coordinate of solvent polarization Δp which is determined by the amount of transferred charge Δe. So he reached a simplification of the energy representation to only two dimensions: G = f(Δe). The result for two conducting spheres in a solvent is the formula of Marcus
Where r 1 and r 2 are the radii of the spheres and R is their separation, ε s and ε opt are the static and high frequency (optical) dielectric constants of the solvent, Δe the amount of charge transferred. The graph of G vs. Δe is a parabola (Fig. 1). In Marcus theory the energy belonging to the transfer of a unit charge (Δe = 1) is called the (outer sphere) reorganization energy λ o , i.e. the energy of a state where the polarization would correspond to the transfer of a unit amount of charge, but the real charge distribution is that before the transfer. [ 9 ] In terms of exchange direction the system is symmetric.
Shrinking the two-sphere model to the molecular level creates the problem that in the self-exchange reaction the charge can no longer be transferred in arbitrary amounts, but only as a single electron. However, the polarization still is determined by the total ensemble of the solvent molecules and therefore can still be treated classically, i.e. the polarization energy is not subject to quantum limitations. Therefore, the energy of solvent reorganization can be calculated as being due to a hypothetical transfer and back transfer of a partial elementary charge according to the Marcus formula. Thus the reorganization energy for chemical redox reactions, which is a Gibbs free energy, is also a parabolic function of Δe of this hypothetical transfer, For the self exchange reaction, where for symmetry reasons Δe = 0.5, the Gibbs free energy of activation is ΔG(0) ‡ = λ o /4 (see Fig. 1 and Fig. 2 intersection of the parabolas I and f, f(0), respectively).
Up to now all was physics, now some chemistry enters. The self exchange reaction is a very specific redox reaction, most of the redox reactions are between different partners [ 10 ] e.g.
and they have positive (endergonic) or negative (exergonic) Gibbs free energies of reaction Δ G ∘ {\displaystyle \Delta G^{\circ }} .
As Marcus calculations refer exclusively to the electrostatic properties in the solvent (outer sphere) Δ G ∘ {\displaystyle \Delta G^{\circ }} and λ 0 {\displaystyle \lambda _{0}} are independent of one another and therefore can just be added up. This means that the Marcus parabolas in systems with different Δ G ∘ {\displaystyle \Delta G^{\circ }} are shifted just up or down in the G {\displaystyle G} vs. Δ e {\displaystyle \Delta e} diagram (Fig. 2). Variation of Δ G ∘ {\displaystyle \Delta G^{\circ }} can be affected in experiments by offering different acceptors to the same donor.
Simple calculation of the intersection point between the parabolas i ( y = x 2 ) {\displaystyle (y=x^{2})} and f i {\displaystyle f_{i}} ( y = ( x − d ) 2 + c ) {\displaystyle (y=(x-d)^{2}+c)} give the Gibbs free energy of activation
where λ 0 {\displaystyle \lambda _{0}} = d 2 {\displaystyle d^{2}} and Δ G ∘ {\displaystyle \Delta G^{\circ }} = c . The intersection of those parabolas represents an activation energy and not the energy of a transition state of fixed configuration of all nuclei in the system as is the case in the substitution and other reactions mentioned. The transition state of the latter reactions has to meet structural and energetic conditions, redox reactions have only to comply to the energy requirement. Whereas the geometry of the transition state in the other reactions is the same for all pairs of reactants, for redox pairs many polarization environments may meet the energetic conditions.
Marcus' formula shows a quadratic dependence of the Gibbs free energy of activation on the Gibbs free energy of reaction. It is general knowledge from the host of chemical experience that reactions usually are the faster the more negative is Δ G ∘ {\displaystyle \Delta G^{\circ }} . In many cases even a linear free energy relation is found. According to the Marcus formula the rates increase also when the reactions are more exergonic, however only as long as Δ G ∘ {\displaystyle \Delta G^{\circ }} is positive or slightly negative. It is surprising that for redox reactions according to the Marcus formula the activation energy should increase for very exergonic reaction, i.e. in the cases when Δ G ∘ {\displaystyle \Delta G^{\circ }} is negative and its absolute value is greater than that of λ 0 {\displaystyle \lambda _{0}} . This realm of Gibbs free energy of reaction is called "Marcus inverted region". In Fig. 2 it becomes obvious that the intersection of the parabolas i and f moves upwards in the left part of the graph when Δ G ∘ {\displaystyle \Delta G^{\circ }} continues to become more negative, and this means increasing activation energy. Thus the total graph of ln k {\displaystyle \ln k} vs. Δ G ∘ {\displaystyle \Delta G^{\circ }} should have a maximum.
The maximum of the ET rate is expected at Δ G ‡ = 0. {\displaystyle \Delta G^{\ddagger }=0.} Here Δ e = 0 {\displaystyle \Delta e=0} and q = 0 {\displaystyle q=0} (Fig. 2) which means that the electron may jump in the precursor complex at its equilibrium polarization. No thermal activation is necessary: the reaction is barrierless. In the inverted region the polarization corresponds to the difficult-to-imagine notion of a charge distribution where the donor has received and the acceptor given off charge. Of course, in real world this does not happen, it is not a real charge distribution which creates this critical polarization, but the thermal fluctuation in the solvent. This polarization necessary for transfer in the inverted region can be created – with some probability – as well as any other one. [ 11 ] The electron is just waiting for it for jumping.
In the outer sphere model the donor or acceptor and the tightly bound solvation shells or the complex' ligands were considered to form rigid structures which do not change in the course of electron transfer. However, the distances in the inner sphere are dependent on the charge of donor and acceptor, e.g. the central ion-ligand distances are different in complexes carrying different charges and again the Franck–Condon principle must be obeyed: for the electron to jump to occur, the nuclei have to have an identical configuration to both the precursor and the successor complexes, of course highly distorted. In this case the energy requirement is fulfilled automatically.
In this inner sphere case the Arrhenius concept holds, the transition state of definite geometric structure is reached along a geometrical reaction coordinate determined by nuclear motions. No further nuclear motion is necessary to form the successor complex, just the electron jumps, which makes a difference to the TST theory. The reaction coordinate for inner sphere energy is governed by vibrations and they differ in the oxidized and reduces species. [ 12 ]
For the self-exchange system Fe 2+ /Fe 3+ only the symmetrical breathing vibration of the six water molecules around the iron ions is considered. [ 12 ] Assuming harmonic conditions this vibration has frequencies ν D {\displaystyle \nu _{D}} and ν A {\displaystyle \nu _{A}} , the force constants f D and f A are f = 4 π 2 ν 2 μ {\displaystyle f=4\pi ^{2}\nu ^{2}\mu } and the energies are
where q 0 is the equilibrium normal coordinate and Δ q = ( q − q 0 ) {\displaystyle \Delta q=(q-q_{0})} the displacement along the normal coordinate, the factor 3 stems from 6 (H 2 O)· 1 ⁄ 2 . Like for the outer-sphere reorganization energy potential energy curve is quadratic, here, however, as a consequence of vibrations.
The equilibrium normal coordinates differ in Fe(H 2 O) 6 2+ and Fe(H 2 O) 6 3+ . By thermal excitation of the breathing vibration a geometry can be reached which is common to both donor and acceptor, i.e. the potential energy curves of the breathing vibrations of D and A intersect here. This is the situation where the electron may jump. The energy of this transition state is the inner sphere reorganization energy λ in .
For the self-exchange reaction the metal-water distance in the transition state can be calculated [ 12 ]
This gives the inner sphere reorganisation energy
It is fortunate that the expressions for the energies for outer and inner reorganization have the same quadratic form. Inner sphere and outer sphere reorganization energies are independent, so they can be added to give λ = λ in + λ o {\displaystyle \lambda =\lambda _{\text{in}}+\lambda _{o}} and inserted in the Arrhenius equation
Here, A can be seen to represent the probability of electron jump, exp[-Δ G in ‡ / kT ] that of reaching the transition state of the inner sphere and exp[-Δ G o ‡ / kT ] that of outer sphere adjustment.
For unsymmetrical (cross) reactions like
the expression for λ i n {\displaystyle \lambda _{in}} can also be derived, but it is more complicated. [ 12 ] These reactions have a free reaction enthalpy ΔG 0 which is independent of the reorganization energy and determined by the different redox potentials of the iron and cobalt couple. Consequently, the quadratic Marcus equation holds also for the inner sphere reorganization energy, including the prediction of an inverted region. One may visualizing this by (a) in the normal region both the initial state and the final state have to have stretched bonds, (b) In the Δ G ‡ = 0 case the equilibrium configuration of the initial state is the stretched configuration of the final state, and (c) in the inverted region the initial state has compressed bonds whereas the final state has largely stretched bonds.
Similar considerations hold for metal complexes where the ligands are larger than solvent molecules and also for ligand bridged polynuclear complexes.
The strength of the electronic coupling of the donor and acceptor decides whether the electron transfer reaction is adiabatic or non-adiabatic. In the non-adiabatic case the coupling is weak, i.e. H AB in Fig. 3 is small compared to the reorganization energy and donor and acceptor retain their identity. The system has a certain probability to jump from the initial to the final potential energy curves. In the adiabatic case the coupling is considerable, the gap of 2 H AB is larger and the system stays on the lower potential energy curve. [ 13 ]
Marcus theory as laid out above, represents the non-adiabatic case. [ 14 ] Consequently, the semi-classical Landau-Zener theory can be applied, which gives the probability of interconversion of donor and acceptor for a single passage of the system through the region of the intersection of the potential energy curves
where H if is the interaction energy at the intersection, v the velocity of the system through the intersection region, s i and s f the slopes there.
Working this out, one arrives at the basic equation of Marcus theory
where k e t {\displaystyle k_{et}} is the rate constant for electron transfer, | H A B | {\displaystyle |H_{AB}|} is the electronic coupling between the initial and final states, λ {\displaystyle \lambda } is the reorganization energy (both inner and outer-sphere), and Δ G ∘ {\displaystyle \Delta G^{\circ }} is the total Gibbs free energy change for the electron transfer reaction ( k B {\displaystyle k_{\rm {B}}} is the Boltzmann constant and T {\displaystyle T} is the absolute temperature ).
Thus Marcus's theory builds on the traditional Arrhenius equation for the rates of chemical reactions in two ways:
1. It provides a formula for the activation energy, based on a parameter called the reorganization energy, as well as the Gibbs free energy. The reorganization energy is defined as the energy required to "reorganize" the system structure from initial to final coordinates, without making the charge transfer.
2. It provides a formula for the pre-exponential factor in the Arrhenius equation, based on the electronic coupling between the initial and final state of the electron transfer reaction (i.e., the overlap of the electronic wave functions of the two states).
Marcus published his theory in 1956. For many years there was an intensive search for the inverted region which would be a proof of the theory. But all experiments with series of reactions of more and more negative ΔG 0 revealed only an increase of the reaction rate up to the diffusion limit, i.e. to a value indicating that every encounter lead to electron transfer, and that limit held also for very negative ΔG 0 values (Rehm-Weller behaviour). [ 15 ] It took about 30 years until the inverted region was unequivocally substantiated by Miller, Calcaterra and Closs for an intramolecular electron transfer in a molecule where donor and acceptor are kept at a constant distance by means of a stiff spacer (Fig.4). [ 16 ]
A posteriori one may presume that in the systems where the reaction partners may diffuse freely the optimum distance for the electron jump may be sought, i.e. the distance for which ΔG ‡ = 0 and ΔG 0 = - λ o . For λ o is dependent on R, λ o increases for larger R and the opening of the parabola smaller. It is formally always possible to close the parabola in Fig. 2 to such an extent, that the f-parabola intersects the i-parabola in the apex. Then always ΔG ‡ = 0 and the rate k reaches the maximum diffusional value for all very negative ΔG 0 . There are, however, other concepts for the phenomenon, [ 1 ] e.g. the participation of excited states or that the decrease of the rate constants would be so far in the inverted region that it escapes measurement.
R. A. Marcus and his coworkers have further developed the theory outlined here in several aspects. They have included inter alia statistical aspects and quantum effects, [ 17 ] they have applied the theory to chemiluminescence [ 18 ] and electrode reactions. [ 19 ] R. A. Marcus received the Nobel Prize in Chemistry in 1992, and his Nobel Lecture gives an extensive view of his work. [ 1 ] | https://en.wikipedia.org/wiki/Marcus_theory |
Marcy Zenobi-Wong is an American engineer and professor of Tissue Engineering and Biofabrication at the Swiss Federal Institute of Technology ( ETH Zurich ). She is known for her work in the field of Tissue Engineering .
Zenobi-Wong completed her undergraduate degree in mechanical engineering at the Massachusetts Institute of Technology , and a graduate degree at Stanford University . [ 1 ] She completed her PhD on the role of mechanical forces in skeletal development in 1990. [ 2 ] After this, she first worked for a year as a postdoc in the Orthopaedic Research Laboratories, University of Michigan , before moving to the University of Bern as group leader Cartilage Biomechanics in 1992, where she habilitated in 2000. In 2003, she moved to ETH Zürich, first to the Institute for Biomedical Engineering, and later to the Department of Health Sciences and Technology, where she became an associate professor in 2017.
Zenobi-Wong works in the area of tissue engineering, in particular for cartilage regeneration. She develops functional biomaterials which mimic the extracellular matrix . The biofabrication techniques used to develop these materials include electrospinning , casting, two-photon polymerization [ 3 ] and bioprinting . [ 4 ]
Zenobi-Wong holds four licensed patents in the fields of tissue engineering, tissue engineering techniques, and gene expression assays. She was one of the originators of the MSc Biomedical Engineering program at ETH Zürich, and developed several graduate level courses in tissue engineering and biomedical engineering. [ 2 ] Zenobi-Wong currently serves as President of the Swiss Society for Biomaterials and Regenerative Medicine, [ 5 ] and as secretary general of the International Society of Biofabrication. [ 6 ] | https://en.wikipedia.org/wiki/Marcy_Zenobi-Wong |
In mathematics , the tameness theorem states that every complete hyperbolic 3-manifold with finitely generated fundamental group is topologically tame , in other words homeomorphic to the interior of a compact 3-manifold.
The tameness theorem was conjectured by Marden (1974) . It was proved by Agol (2004) and, independently, by Danny Calegari and David Gabai . It is one of the fundamental properties of geometrically infinite hyperbolic 3-manifolds, together with the density theorem for Kleinian groups and the ending lamination theorem .
It also implies the Ahlfors measure conjecture .
Topological tameness may be viewed as a property of the ends of the manifold, namely, having a local product structure. An analogous statement is well known in two dimensions, that is, for surfaces . However, as the example of Alexander horned sphere shows, there are wild embeddings among 3-manifolds, so this property is not automatic.
The conjecture was raised in the form of a question by Albert Marden , who proved that any geometrically finite hyperbolic 3-manifold is topologically tame. The conjecture was also called the Marden conjecture or the tame ends conjecture .
There had been steady progress in understanding tameness before the conjecture was resolved. Partial results had been obtained by Thurston , Brock, Bromberg, Canary, Evans, Minsky, Ohshika. [ citation needed ] An important sufficient condition for tameness in terms of splittings of the fundamental group had been obtained by Bonahon . [ citation needed ]
The conjecture was proved in 2004 by Ian Agol , and independently, by Danny Calegari and David Gabai. Agol's proof relies on the use of manifolds of pinched negative curvature and on Canary's trick of "diskbusting" that allows to replace a compressible end with an incompressible end, for which the conjecture has already been proved. The Calegari–Gabai proof is centered on the existence of certain closed, non-positively curved surfaces that they call "shrinkwrapped". | https://en.wikipedia.org/wiki/Marden_tameness_conjecture |
Marek Strandberg (born 25 September 1965 in Tallinn ) is an Estonian materials scientist , businessman, caricaturist and politician. He has been member of XI Riigikogu . [ 1 ]
He is a member of Estonian Greens . [ 1 ]
This article about a member of the Riigikogu, 2007–2011 is a stub . You can help Wikipedia by expanding it .
This Estonian academic-related biographical article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Marek_Strandberg |
Marfeel, Inc. is an ad tech platform that allows publishers to create, optimize and monetize their mobile websites .
The company was founded in Barcelona on October 6, 2011 by Xavi Beumala and Juan Margenat , with the two also acting as the company's executives.
Marfeel was established in 2011 in Barcelona by Xavi Beumala, and Juan Margenat; Beumala was an Adobe employee, while Margenat was a civil engineer active in Barcelona's startup scene. [ 1 ] [ 2 ] [ 3 ] Shortly after its establishment, Marfeel participated in The TechCrunch Barcelona Meetup , where it won the competition. [ 4 ] [ 5 ] Prior to requesting its first funding, the company was accepted in two startup accelerators: Wayra , Telefónica's 's accelerator and SeedRocket. [ 6 ] [ 7 ] [ 8 ] The company's concept originated from Beumala's observation that many websites offered inefficient mobile versions of their desktop counterparts. [ 2 ] [ 9 ]
Marfeel raised $2 million in 2013, in a Series A round . The round was led by Nauta Capital, with Elaia Partners, BDMI , and Wayra also investing. [ 1 ] [ 10 ] After announcing a 300% growth in 2015, Marfeel was listed in The Next Web's European Tech5 in March 2015. [ 11 ] [ 12 ] In January 2015, Marfeel became a certified Google partner, becoming Spain's first Google recommended mobile vendor. [ 13 ] The company initiated a Series B funding round in late 2015, receiving a sum of $3.5 million. [ 14 ] Marfeel aimed at using the funding to open an office in New York , expand its business the United States, and improve its technology. [ 15 ] [ 16 ] [ 17 ]
In April 2016, TechCrunch announced Marfeel's full support for Facebook 's newly-launched Instant Articles, [ 18 ] providing a mobile publishing format that enables news publishers to distribute articles to Facebook's app, loading and displaying content significantly faster than the standard mobile web, within Facebook itself. Marfeel customer websites are fully Instant Articles- enabled and optimized.
Marfeel has developed a platform that creates a mobile website for online publications, optimizing the traffic, engagement, and monetization of their website. [ 17 ] [ 19 ] | https://en.wikipedia.org/wiki/Marfeel |
Margaret Helen Harper (9 February 1919 - 13 October 2014) [ 1 ] [ 2 ] [ 3 ] was an American computer programmer who worked with Grace Hopper at Remington Rand to develop one of the first computer compilers . [ 1 ] [ 4 ] Harper was born in Michigan, but lived most of her life in Pennsylvania. [ 2 ] She attended Wellesley College and graduated from the University of Pennsylvania in 1940. [ 5 ] She worked as a programmer and then as a professor. [ 1 ]
Harper was born in Michigan , but grew up in Pennsylvania . [ 2 ] Her parents were Paul Harper (b. 1892) and Katharine Harper (b. 1893). [ 2 ] Paul worked at an auto dealership, and Katharine was a musician and a stay-at-home mother. [ 1 ] Margaret had an adopted younger brother named Richard Irving Harper (13 March 1927 - November 1977). [ 2 ] [ 6 ] Margaret was encouraged in her studies as a child, but she lamented that she wasn't very artistic. [ 1 ] Margaret attended both public and private schools before her college years. [ 1 ] For college, Margaret first attended Wellesley College , but then transferred to the University of Pennsylvania . [ 1 ] [ 5 ] Margaret was active in sports, and played on the Wellesley College and University of Pennsylvania women's hockey teams. [ 5 ] [ 7 ] Margaret graduated in 1940 with a Bachelor of Science from the University of Pennsylvania's School of Education where she studied chemistry . [ 1 ] [ 5 ] [ 8 ] [ 9 ]
It is not clear how Harper got involved in computer science, but by the 1950s she was working as a developer. [ 1 ]
Computer science is by and large a discipline of collaboration, and the development process in the late 1940s and early 1950s was no different in that respect. In the early 1950s when Grace Hopper was developing the first compilers , she was aided by Harper and Richard K. Ridgway . [ 10 ] [ 11 ] Hopper even stated that "this work is necessarily group research, and this account cannot be published without citing those members…primarily responsible for the achievement of these results". [ 1 ] This is important to note, because much of Harper's contribution has been overshadowed by the Matilda Effect of Grace Hopper's fame. In 1952, Harper, Ridgway, and Hopper were all working at Remington Rand on the A series of compilers for the UNIVAC system . Specifically, Harper and Ridgway prepared the manual for and worked on the A-2 compiler. [ 11 ]
Harper also published her article "Subroutines: Prefabricated Blocks for Building" in the March 1954 issue of Computers and Automation . [ 12 ] In her article, Harper starts off by saying how the 1950s computer programmer has essentially been like a "settler in America" who must make every bit of his house by hand, right down to the pegs that hold the house together! [ 12 ] She continues by noting that the times have changed, and now programmers are working together not from the fine pegs of a house, but by using the tools and ideas that others discovered in the past. [ 12 ] She stresses the importance of subroutines in computer programming—the idea that larger tasks can be broken down into smaller (sub) segments—but goes on to note that "the absence of a compiler [for subroutines] has meant that subroutines have been coded to function only in a fixed portion of the computer's storage or memory." [ 12 ] This was problematic, because it meant that a lot of code was simply not reusable . The computers that we know and recognize today (in the 2000s) could not function without this reusable code. But in 1954 Harper had the foresight to ask, "If Russian can be translated into English…why not one computer code into another?" [ 13 ] [ 12 ] This was the crux of the issue with in the idea of compiler design and implementation. Although Harper did not invent the compiler, she was a part of one of the earliest teams of scientists who would imagine and build the first compilers. The New Scientist from 17 September 1987 states that one of the first people to implement the new compilers was Harper. [ 14 ]
After Harper finished work with Hopper and Ridgway at Remington Rand, she continued as a programming analyst at Auerbach Corporation in the 1960s. [ 9 ] [ 1 ] She was among those listed in the Who's Who in the Computer Field for 1963-64 [ 8 ] and the Who's Who in Computers and Data Processing for 1971. [ 9 ] [ 1 ] After working for Auerbach, she taught at the university of a Pennsylvania and later retired. [ 1 ]
She died in 2014 in Pennsylvania at the age of 95. [ 3 ] | https://en.wikipedia.org/wiki/Margaret_Helen_Harper |
Margaret Melhase Fuchs (August 13, 1919 – August 8, 2006) was an American chemist and a co-discoverer, with Glenn T. Seaborg , of the isotope caesium-137 . [ 3 ] [ 4 ]
In 1940, Melhase was an undergraduate in the college of chemistry at the University of California, Berkeley . She was president of the Student Affiliates of the American Chemical Society and was considering doctoral studies and a career in chemistry. [ 5 ] Honors students typically took on research projects at the time, and she sought advice from her close friend, nuclear chemist Gerhart Friedlander ; Friedlander was then a graduate student under the supervision of Glenn T. Seaborg , and he suggested she approach him for a project. [ 5 ] She spoke to Seaborg in his lab, and he proposed they work together to search for a Group 1 element among the fission products of uranium . Her laboratory was above those of Nobel Prize winners Willard Libby and Melvin Calvin . [ 5 ]
In March 1941, Melhase worked with Art Wahl . He handed her 100 grams of a uranium compound ( uranyl nitrate ) that had been neutron-irradiated by a cyclotron . [ 6 ] [ 5 ] Using a Lauritzen quartz fiber electroscope , she discovered the Cs-137 several months later. [ 7 ] [ 6 ] Despite establishing herself as a promising young experimental scientist, nuclear research during World War II was treated with strict secrecy and it was not publicized. [ 5 ] Significant research on the isotope followed, but their results were not made available until after the war. [ 7 ]
Melhase received a bachelor's degree in nuclear chemistry and planned to apply for graduate studies at UC Berkeley. However, the head of the chemistry department, Gilbert N. Lewis , was refusing entry to women; the last woman the department admitted had gotten married shortly after her graduation and he considered her education a "waste". [ 1 ] [ 7 ] She worked for the Philadelphia Quartz Company in El Cerrito, California . [ 6 ] She rejoined the Manhattan Project from 1944 to 1946. [ 6 ] Without an advanced degree, she did not continue her career in science. [ 5 ]
Though references to her work are scant, Seaborg shares credit of his discovery of Cs-137 with her. Writing in 1961, he stated: [ 5 ]
I am considering including a short description of the discovery of radioactive cesium 137 in one of my talks. I believe that the work you did with me during 1941 on the identification of this isotope as a fission product of uranium constitutes the first observation of this isotope.
He also wrote in 1990 that "it is appropriate to credit both G. T. Seaborg and M. Melhase for the 'birth' of cesium 137." [ 5 ]
Margaret was an only child, born in Berkeley, California to mother Margaret Orchard and father John Melhase, who worked as a geologist. [ 1 ] During her time at UC Berkeley, Melhase was a member of the Berkeley Folk Dancers and edited the group's newsletter. [ 8 ] [ 9 ] [ 10 ] She met mathematics professor Robert A. Fuchs at a folk dance, and the two married in 1945 and had three children. [ 1 ] She and her husband moved to Los Angeles . [ 8 ] She was a supporter of social causes, organizing marches for agricultural workers and housing and aiding immigrant Laotian families in Los Angeles. [ 1 ] | https://en.wikipedia.org/wiki/Margaret_Melhase |
In toxicology , the margin of exposure (or MOE ) of a substance is the ratio of its no-observed-adverse-effect level to its theoretical, predicted, or estimated dose or concentration of human intake. [ 1 ] It is used in risk assessment to determine the dangerousness of substances that are both genotoxic and carcinogenic . [ 2 ] This approach is preferred by both the World Health Organization and the European Food Safety Authority for the evaluation of the risk of carcinogens. [ 3 ]
This toxicology -related article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Margin_of_exposure |
Marginal-zone B cells (MZ B cells) are noncirculating mature B cells that in humans segregate anatomically into the marginal zone (MZ) of the spleen [ 1 ] and certain other types of lymphoid tissue . [ 2 ] The MZ B cells within this region typically express low-affinity polyreactive B-cell receptors (BCR), high levels of IgM , Toll-like receptors (TLRs), CD21 , CD1 , CD9 , CD27 with low to negligible levels of secreted- IgD , CD23 , CD5 , and CD11b that help to distinguish them phenotypically from follicular (FO) B cells and B1 B cells . [ 2 ] [ 3 ]
MZ B cells are innate-like B cells specialized to mount rapid T-independent, but also T-dependent responses against blood-borne pathogens. [ 4 ] They are also known to be the main producers of IgM antibodies in humans. [ 5 ]
The spleen's marginal zone contains multiple subtypes of macrophages and dendritic cells interlaced with the MZ B cells; it is not fully formed until 2 to 3 weeks after birth in rodents and 1 to 2 years in humans. [ 6 ] In humans, but not rodents, marginal zone B cells are also located in the inner wall of the subcapsular sinus of lymph nodes, the epithelium of tonsillar crypts , and the sub-epithelial area of mucosa-associated lymphoid tissues including the sub-epithelial dome of intestinal Peyer's patches . [ 2 ] Human MZ B cells are also present in peripheral blood, suggesting that they recirculate. [ 7 ] However, in mice they seem to be noncirculating and only limited to follicular shuttling. [ 2 ]
In rodents, MZ B cells are recognized as IgM high IgD low CD21 high CD23 low population of B cells. They are furthermore distinguished by the expression of CD9 [ 3 ] and CD27 (in humans). [ 2 ] In mice, MZ B cells characteristically express high levels of CD1d , which is an MHC class I -like molecule involved in the presentation of lipid molecules to NKT cells . [ 8 ] Unlike FO B cells, MZ B cells express polyreactive BCRs that bind to multiple microbial molecular patterns . Additionally, they express high levels of TLRs . [ 2 ]
In specimens where the tyrosine kinase for Pyk-2 has been knocked-out, marginal zone B-cells will fail to develop while B-1 cells will still be present. MZ B-cells are the only B-cells dependent on NOTCH2 signaling for proliferation. [ 9 ]
Similar to B1 B cells , MZ B cells can be rapidly recruited into the early adaptive immune responses in a T cell -independent manner. [ 9 ] The MZ B cells are especially well-positioned as the first line of defense against systemic blood-borne antigens that enter the circulation and become trapped in the spleen. [ 10 ] While large blood-borne antigens are captured by dendritic cells , circulating granulocytes or MZ macrophages , smaller blood-borne antigens may directly interact with MZ B cells situated on the exterior of the marginal sinus. [ 2 ] [ 4 ] MZ B cells shuttle between the blood-filled marginal zone for antigen collection and the follicle for antigen delivery to follicular dendritic cells . In mice, it has been shown that these cells shear flow via the LFA-1 integrin ligand ICAM-1 and adhere or migrate down the flow via the VLA-4 integrin ligand VCAM-1 . While CXCR5 / CXCL13 signaling is required for MZ B cells to enter the follicle, Sphingosine-1-phosphate signaling is required for them to exit from the follicle. [ 11 ]
MZ B cells respond to a wide spectrum of T-independent, but also T-dependent antigens. It is believed that MZ B cells are especially reactive to microbial polysaccharide antigens of encapsulated bacteria such as Streptococcus pneumoniae , Haemophilus influenzae and Neisseria meningitidis . TLRs often activate MZ B cells after recognizing microbial molecular structures in cooperation with the BCR . [ 7 ] These innate-like B cells provide a rapid first line of defense against blood-borne pathogens and produce low-affinity antibodies of wide specificity before the induction of T-cell-dependent high-affinity antibody responses. Therefore MZ B cells may play an important role in the prevention of sepsis . [ 8 ] MZ B cells also display a lower activation threshold than their FO B cell counterparts, with a heightened propensity for plasma cell differentiation that contributes further to the accelerated primary antibody response. [ 2 ] [ 12 ] They have been acknowledged as the main producers of IgM antibodies in humans. [ 5 ]
They are important for antibody-response toward invading pathogens and maintaining homeostasis via opsonization of dead cells and cellular debris. [ 5 ] Moreover, MZ B cells are potent antigen-presenting cells , that are able to activate CD4+ T cells more effectively than FO B cells due to their elevated expression levels of MHC class II , CD80 and CD86 molecules. [ 2 ] [ 7 ]
Deficiencies of MZ B cells are associated with a higher risk of pneumococcal infection , meningitis and insufficient antibody response to capsular polysaccharides. [ 2 ] [ 4 ]
In humans the splenic marginal zone B cells have evidence of somatic hypermutation in their immunoglobulin genes, indicating that they have been generated through a germinal centre reaction to become memory cells . While naive MZ B cells produce low-affinity IgM antibodies, memory MZ B cells express high-affinity Ig molecules. Besides unswitched cells (IgM+), class-switched B cells can be found in the human and rodent marginal zone ( IgG + and IgA +). In humans, MZ B cells express CD27 , which is a member of the TNF-receptor family expressed by human memory B cells. [ 8 ]
Many of MZ B cell-receptors are self-reactive, which may be a factor that contributes to their expansion in some autoimmune diseases . On the other hand, aiding in the clearance of self-antigens is considered an important mechanism to prevent the development of autoimmune diseases. The role of expanded self-reactive MZ B cells has been observed on mice models of lupus , diabetes and arthritis . [ 7 ] However, their levels in human vasculitis are reduced. [ 5 ]
Marginal zone B cells are the malignant cells in marginal zone lymphomas , a heterogeneous group of generally indolent lymphomas . [ 13 ] | https://en.wikipedia.org/wiki/Marginal-zone_B_cell |
The marginal sinus is a dural venous sinus surrounding the margin of the foramen magnum inside the skull, [ 2 ] accommodated by the groove for marginal sinus. [ 3 ] It usually drains into either the sigmoid sinus , or the jugular bulb . It communicates with the basilar venous plexus anteriorly, and the occipital sinus posteriorly (the posterior union of the left and the right marginal sinus usually representing the commencement of the occipital sinus [ 2 ] ); it may form extracranial communications with the internal vertebral venous plexuses , or deep cervical veins . [ 4 ]
Arteriovenous fistulas involving the marginal sinus have been described - often following basilar skull fractures . [ 2 ]
The marginal sinus must be traversed during surgical entry into subdural space deep to the foramen magnum. [ 2 ] | https://en.wikipedia.org/wiki/Marginal_sinus |
In the theory of dynamical systems and control theory , a linear time-invariant system is marginally stable if it is neither asymptotically stable nor unstable . Roughly speaking, a system is stable if it always returns to and stays near a particular state (called the steady state ), and is unstable if it goes further and further away from any state, without being bounded. A marginal system, sometimes referred to as having neutral stability, [ 1 ] is between these two types: when displaced, it does not return to near a common steady state, nor does it go away from where it started without limit.
Marginal stability, like instability, is a feature that control theory seeks to avoid; we wish that, when perturbed by some external force, a system will return to a desired state. This necessitates the use of appropriately designed control algorithms.
In econometrics , the presence of a unit root in observed time series , rendering them marginally stable, can lead to invalid regression results regarding effects of the independent variables upon a dependent variable , unless appropriate techniques are used to convert the system to a stable system.
A homogeneous continuous linear time-invariant system is marginally stable if and only if the real part of every pole ( eigenvalue ) in the system's transfer-function is non-positive , one or more poles have zero real part, and all poles with zero real part are simple roots (i.e. the poles on the imaginary axis are all distinct from one another). In contrast, if all the poles have strictly negative real parts, the system is instead asymptotically stable. If the system is neither stable nor marginally stable, it is unstable.
If the system is in state space representation , marginal stability can be analyzed by deriving the Jordan normal form : [ 2 ] if and only if the Jordan blocks corresponding to poles with zero real part are scalar is the system marginally stable.
A homogeneous discrete time linear time-invariant system is marginally stable if and only if the greatest magnitude of any of the poles (eigenvalues) of the transfer function is 1, and the poles with magnitude equal to 1 are all distinct. That is, the transfer function's spectral radius is 1. If the spectral radius is less than 1, the system is instead asymptotically stable.
A simple example involves a single first-order linear difference equation : Suppose a state variable x evolves according to
with parameter a > 0. If the system is perturbed to the value x 0 , {\displaystyle x_{0},} its subsequent sequence of values is a x 0 , a 2 x 0 , a 3 x 0 , … . {\displaystyle ax_{0},\,a^{2}x_{0},\,a^{3}x_{0},\,\dots .} If a < 1, these numbers get closer and closer to 0 regardless of the starting value x 0 , {\displaystyle x_{0},} while if a > 1 the numbers get larger and larger without bound. But if a = 1, the numbers do neither of these: instead, all future values of x equal the value x 0 . {\displaystyle x_{0}.} Thus the case a = 1 exhibits marginal stability.
A marginally stable system is one that, if given an impulse of finite magnitude as input, will not "blow up" and give an unbounded output, but neither will the output return to zero. A bounded offset or oscillations in the output will persist indefinitely, and so there will in general be no final steady-state output. If a continuous system is given an input at a frequency equal to the frequency of a pole with zero real part, the system's output will increase indefinitely (this is known as pure resonance [ 3 ] ). This explains why for a system to be BIBO stable , the real parts of the poles have to be strictly negative (and not just non-positive).
A continuous system having imaginary poles, i.e. having zero real part in the pole(s), will produce sustained oscillations in the output. For example, an undamped second-order system such as the suspension system in an automobile (a mass–spring–damper system), from which the damper has been removed and spring is ideal, i.e. no friction is there, will in theory oscillate forever once disturbed. Another example is a frictionless pendulum . A system with a pole at the origin is also marginally stable but in this case there will be no oscillation in the response as the imaginary part is also zero ( jw = 0 means w = 0 rad/sec). An example of such a system is a mass on a surface with friction. When a sidewards impulse is applied, the mass will move and never returns to zero. The mass will come to rest due to friction however, and the sidewards movement will remain bounded.
Since the locations of the marginal poles must be exactly on the imaginary axis or unit circle (for continuous time and discrete time systems respectively) for a system to be marginally stable, this situation is unlikely to occur in practice unless marginal stability is an inherent theoretical feature of the system.
Marginal stability is also an important concept in the context of stochastic dynamics . For example, some processes may follow a random walk , given in discrete time as
where e t {\displaystyle e_{t}} is an i.i.d. error term . This equation has a unit root (a value of 1 for the eigenvalue of its characteristic equation ), and hence exhibits marginal stability, so special time series techniques must be used in empirically modeling a system containing such an equation.
Marginally stable Markov processes are those that possess null recurrent classes. | https://en.wikipedia.org/wiki/Marginal_stability |
The marginal value theorem ( MVT ) is an optimality model that usually describes the behavior of an optimally foraging individual in a system where resources (often food) are located in discrete patches separated by areas with no resources. Due to the resource-free space, animals must spend time traveling between patches. The MVT can also be applied to other situations in which organisms face diminishing returns .
The MVT was first proposed by Eric Charnov in 1976. In his original formulation: "The predator should leave the patch it is presently in when the marginal capture rate in the patch drops to the average capture rate for the habitat." [ 1 ]
All animals must forage for food in order to meet their energetic needs, but doing so is energetically costly. It is assumed that evolution by natural selection results in animals utilizing the most economic and efficient strategy to balance energy gain and consumption. The Marginal Value Theorem is an optimality model that describes the strategy that maximizes gain per unit time in systems where resources, and thus rate of returns, decrease with time. [ 2 ] The model weighs benefits and costs and is used to predict giving up time and giving up density. Giving up time (GUT) is the interval of time between when the animal last feeds and when it leaves the patch. Giving up density (GUD) is the food density within a patch when the animal will choose to move on to other food patches.
When an animal is foraging in a system where food sources are patchily distributed, the MVT can be used to predict how much time an individual will spend searching for a particular patch before moving on to a new one. In general, individuals will stay longer if (1) patches are farther apart or (2) current patches are poor in resources. Both situations increase the ratio of travel cost to foraging benefit.
As animals forage in patchy systems, they balance resource intake, traveling time, and foraging time. Resource intake within a patch diminishes with time, as shown by the solid curve in the graph to the right. The curve follows this pattern because resource intake is initially very fast, but slows as the resource is depleted. Traveling time is shown by the distance from the leftmost vertical dotted line to the y-axis. Optimal foraging time is modeled by connecting this point on the x-axis tangentially to the resource intake curve. Doing so maximizes the ratio between resource intake and time spent foraging and traveling.
At the extremes of the loading curve, animals spend too much time traveling for a small payoff, or they search too long in a given patch for an ineffective load. The MVT identifies the best possible intermediate between these extremes.
A common illustration of the MVT is apple picking in humans. When one first arrives at a new apple tree, the number of apples picked per minute is high, but it rapidly decreases as the lowest-hanging fruits are depleted. Strategies in which too few apples are picked from each tree or where each tree is exhausted are suboptimal because they result, respectively, in time lost travelling among trees or picking the hard to find last few apples from a tree. The optimal time spent picking apples in each tree is thus a compromise between these two strategies, which can be quantitatively found using the MVT.
Great tits are a species of bird found throughout Europe, northern Africa, and Asia. They are known to forage in “patchy” environments, and research has shown that their behavior can be modeled by optimal foraging models , including the MVT. In a 1977 study by R.A. Cowie, [ 3 ] birds were deprived of food and then allowed to forage through patches in two different environments (the environments differed only in distance between patches). As predicted, in both cases birds spent more time in one area when the patches were farther away or yielded more benefits, regardless of the environment. In a similar experiment by Naef-Daenzer (1999), [ 4 ] great tits were shown to have a foraging efficiency 30% better than random foraging would yield. This is because great tits were specifically spending more time in resource-rich areas, as predicted by the MVT. This data supports the use of the MVT in predicting the foraging behavior of great tits.
Experimental evidence has shown that screaming hairy armadillos and guinea pigs qualitatively follow MVT when foraging. [ 5 ] The researchers ran several parallel experiments: one for each animal under consistent patch quality, and one for guinea pigs with varying patch quality. While the qualitative foraging trend was shown to follow MVT in each case, the quantitative analysis indicated that each patch was exploited further than expected.
The MVT can be used to model foraging in plants as well as animals. Plants have been shown to preferentially place their roots, which are their foraging organs, in areas of higher resource concentration. Recall that the MVT predicts that animals will forage for longer in patches with higher resource quality. Plants increase root biomass in layers/areas of soil that are rich in nutrients and resources, and decrease root growth into areas of poor-quality soil. Thus, plants grow roots into patches of soil according to their wealth of resources in a manner consistent with the MVT. [ 6 ] Additionally, plant roots grow more quickly through low-quality patches of soil than through high-quality patches of soil, just as foraging animals are predicted to spend less time in low-quality areas than high-quality areas.
The MVT can be applied to situations other than foraging in which animals experience diminished returns. Consider, for example, the mating copulation duration of the yellow dung fly . In the dung fly mating system, males gather on fresh cow droppings and wait for females to arrive in smaller groups to lay their eggs. Males must compete with each other for the chance to mate with arriving females—sometimes one male will kick another male off of a female and take over mating with the female mid-copulation. In this instance, the second male fertilizes about 80% of the eggs. [ 7 ] Thus, after a male has mated with a female he guards her so that no other males will have the opportunity to mate with her and displace his sperm before she lays her eggs. After the female lays her eggs, the male must take the time to search for another female before he is able to copulate again.
The question, then, is how long the dung fly should spend copulating with each female. On one hand, the longer a male dung fly copulates the more eggs he can fertilize. However, the benefits of extra copulation time diminish quickly, as the male loses the chance to find another female during long copulations. The MVT predicts that the optimal copulation time is just long enough to fertilize about 80% of the eggs; after this time, the rewards are much smaller and are not worth missing out on another mate. [ 7 ] This predicted value for copulation time, 40 minutes, is very close to the average observed value, 36 minutes.
In dung flies, the observed values of copulation time and time searching for another mate vary with body weight. Heavier males have shorter search times and shorter copulation times. These shorter search times are likely due to increased cost of travel with increased body weight; shorter copulation times probably reflect that it is easier for heavier males to successfully take over females mid-copulation. Additionally, researchers have taken into account “patch quality,” i.e. the quality of females arriving on the various cowpats. Research also shows that males copulate for longer with the larger females who hold more eggs and have larger reproductive tract dimensions. Thus, males change their copulation time to maximize their fitness, but they are doing so in response to selection imposed by female morphology. Even with these variations, male dung flies do exhibit close-to-optimal copulation time relative to their body size, as predicted by the MVT. [ 8 ]
Many studies, such as the examples presented above, have shown good qualitative support for predictions generated by the Marginal Value Theorem. However, in some more quantitative studies, the predictions of the MVT haven’t been as successful, with the observed values substantially deviating from predictions. One proposed explanation for these deviations is that it is difficult to objectively measure payoff rates. For example, an animal in an unpredictable environment may need to spend extra time sampling, making it hard for researchers to determine foraging time. [ 9 ]
Beyond this imprecision, some researchers propose that there is something fundamental missing from the model. Namely, animals are probably doing more than just foraging, whether it be dealing with predation risks or searching for mating opportunities. [ 9 ] Natural selection is not the only force influencing the evolution of species. Sexual selection, for example, may alter foraging behaviors, making them less consistent with the MVT. These researchers point out that the marginal value theorem is a starting point, but complexity and nuances must be incorporated into models and tests for foraging and patch-use.
One other type of model that has been used in place of MVT in predicting foraging behavior is the state-dependent behavior model. Although state-dependent models have been viewed as a generalization of the MVT, [ 10 ] they are unlikely to generate broadly applicable predictions like those from the MVT because they test predictions under a specific set of conditions. While the predictions of these models must be tested under precise conditions, they might offer valuable insights not available from broader models such as MVT. [ 9 ] | https://en.wikipedia.org/wiki/Marginal_value_theorem |
Margot Dorenfeldt (1895–1986) was the first woman to graduate from Norwegian Institute of Technology (1919) and specialized in inorganic chemistry and electrochemistry. She published several papers in radiochemistry . [ 1 ]
She was the daughter of Lauritz J. Dorenfeldt (1863–1932), an engineer who was educated in Berlin, and the granddaughter of businessman Lauritz Dorenfeldt Jenssen (1837–1899). Her mother was Aagot Bødtker (1869–1963). Margot was born 2 October 1895 in Worms , Germany, when her family was there; her father was working on assignment as technical director of a cellulose factory. [ 2 ]
Margot Dorenfeldt was the second woman to enroll at the Norwegian Institute of Technology (NTH) after Aslaug Urbye (who enrolled in 1910, but never completed her studies). In 1919, Dorenfeldt became the first woman to graduate from NTH. While in college, she was active in student debates and made critical comments about her fellow engineers and their record of participation in social politics. [ 1 ]
Dorenfeldt found her first job in 1920 as an assistant at the chemistry laboratory at Royal Frederick University (now University of Oslo ). A few months later, she was promoted to a secretary-like position, from which she could perform research and teach. Soon she was investigating the atomic weight of chlorine while working with the radiochemist and associate professor Ellen Gleditsch , who had previously worked with Marie Curie in Paris. [ 3 ] [ 4 ] Dorenfeldt helped publish their results in English, German and French. [ 1 ] [ 5 ] [ 6 ] [ 7 ]
In 1922, the university granted Dorenfeldt a scholarship so she could study at the Collège de France in Paris. While there she met and married a fellow Norwegian and changed her name to Margot Dorenfeldt Holtan. She published research using her married name as well as her maiden name. [ 3 ] [ 6 ]
As a wife and mother of two, Margot attended to her family but continued working in the field as a part-time secretary and chemist and, according to her own records, she also published scientific work with her husband. Throughout her life, she remained close to her father and his business interests and she took a government position in 1946 and then became an association board member from which she could help protect the interests of his pulp and paper businesses. [ 1 ]
She was married on 23 February 1923 in Paris to Norwegian engineer Eugen Nannestad Holtan (1893–1959). [ 1 ] | https://en.wikipedia.org/wiki/Margot_Dorenfeldt |
The Margules activity model is a simple thermodynamic model for the excess Gibbs free energy of a liquid mixture introduced in 1895 by Max Margules . [ 1 ] [ 2 ] After Lewis had introduced the concept of the activity coefficient , the model could be used to derive an expression for the activity coefficients γ i {\displaystyle \gamma _{i}} of a compound i in a liquid, a measure for the deviation from ideal solubility, also known as Raoult's law .
In 1900, Jan Zawidzki proved the model via determining the composition of binary mixtures condensed at different temperatures by their refractive indices. [ 3 ]
In chemical engineering the Margules Gibbs free energy model for liquid mixtures is better known as the Margules activity or activity coefficient model. Although the model is old it has the characteristic feature to describe extrema in the activity coefficient, which modern models like NRTL and Wilson cannot.
Margules expressed the intensive excess Gibbs free energy of a binary liquid mixture as a power series of the mole fractions x i :
In here the A, B are constants, which are derived from regressing experimental phase equilibria data.
Frequently the B and higher order parameters are set to zero. The leading term X 1 X 2 {\displaystyle X_{1}X_{2}} assures that the excess Gibbs energy becomes zero at x 1 =0 and x 1 =1.
The activity coefficient of component i is found by differentiation of the excess Gibbs energy towards x i .
This yields, when applied only to the first term and using the Gibbs–Duhem equation ,: [ 4 ]
In here A 12 and A 21 are constants which are equal to the logarithm of the limiting activity coefficients: ln ( γ 1 ∞ ) {\displaystyle \ln \ (\gamma _{1}^{\infty })} and ln ( γ 2 ∞ ) {\displaystyle \ln \ (\gamma _{2}^{\infty })} respectively.
When A 12 = A 21 = A {\displaystyle A_{12}=A_{21}=A} , which implies molecules of same molecular size but different polarity, the equations reduce to the one-parameter Margules activity model:
In that case the activity coefficients cross at x 1 =0.5 and the limiting activity coefficients are equal. When A=0 the model reduces to the ideal solution, i.e. the activity of a compound is equal to its concentration (mole fraction).
Using simple algebraic manipulation, it can be stated that d ln γ 1 / d x 1 {\displaystyle d\ln \gamma _{1}/dx_{1}} increases or decreases monotonically within all x 1 {\displaystyle x_{1}} range, if A 12 < 0 {\displaystyle A_{12}<0} or A 21 > 0 {\displaystyle A_{21}>0} with 0.5 < A 12 / A 21 < 2 {\displaystyle 0.5<A_{12}/A_{21}<2} , respectively.
When A 12 < A 21 / 2 {\displaystyle A_{12}<A_{21}/2} and A 12 < 0 {\displaystyle A_{12}<0} , the activity coefficient curve of component 1 shows a maximum and compound 2 minimum at:
Same expression can be used when A 12 < A 21 / 2 {\displaystyle A_{12}<A_{21}/2} and A 12 > 0 {\displaystyle A_{12}>0} , but in this situation the activity coefficient curve of component 1 shows a minimum and compound 2 a maximum.
It is easily seen that when A 12 =0 and A 21 >0 that a maximum in the activity coefficient of compound 1 exists at x 1 =1/3. Obviously, the activity coefficient of compound 2 goes at this concentration through a minimum as a result of the Gibbs-Duhem rule .
The binary system Chloroform(1)-Methanol(2) is an example of a system that shows a maximum in the activity coefficient of Chloroform. The parameters for a description at 20 °C are A 12 =0.6298 and A 21 =1.9522. This gives a minimum in the activity of Chloroform at x 1 =0.17.
In general, for the case A=A 12 =A 21 , the larger parameter A, the more the binary systems deviates from Raoult's law; i.e. ideal solubility. When A>2 the system starts to demix in two liquids at 50/50 composition; i.e. plait point is at 50 mol%. Since:
For asymmetric binary systems, A 12 ≠A 21 , the liquid-liquid separation always occurs for
Or equivalently:
The plait point is not located at 50 mol%. It depends on the ratio of the limiting activity coefficients.
An extensive range of recommended values for the Margules parameters can be found in the literature. [ 6 ] [ 7 ] Selected values are provided in the table below. | https://en.wikipedia.org/wiki/Margules_activity_model |
In differential geometry , the Margulis lemma (named after Grigory Margulis ) is a result about discrete subgroups of isometries of a non-positively curved Riemannian manifold (e.g. the hyperbolic n-space ). Roughly, it states that within a fixed radius, usually called the Margulis constant , the structure of the orbits of such a group cannot be too complicated. More precisely, within this radius around a point all points in its orbit are in fact in the orbit of a nilpotent subgroup (in fact a bounded finite number of such).
The Margulis lemma can be formulated as follows. [ 1 ]
Let X {\displaystyle X} be a simply-connected manifold of non-positive bounded sectional curvature . There exist constants C , ε > 0 {\displaystyle C,\varepsilon >0} with the following property. For any discrete subgroup Γ {\displaystyle \Gamma } of the group of isometries of X {\displaystyle X} and any x ∈ X {\displaystyle x\in X} , if F x {\displaystyle F_{x}} is the set:
then the subgroup generated by F x {\displaystyle F_{x}} contains a nilpotent subgroup of index less than C {\displaystyle C} . Here d {\displaystyle d} is the distance induced by the Riemannian metric.
An immediately equivalent statement can be given as follows: for any subset F {\displaystyle F} of the isometry group, if it satisfies that:
then ⟨ F ⟩ {\displaystyle \langle F\rangle } contains a nilpotent subgroup of index ≤ C {\displaystyle \leq C} .
The optimal constant ε {\displaystyle \varepsilon } in the statement can be made to depend only on the dimension and the lower bound on the curvature; usually it is normalised so that the curvature is between -1 and 0. It is usually called the Margulis constant of the dimension.
One can also consider Margulis constants for specific spaces. For example, there has been an important effort to determine the Margulis constant of the hyperbolic spaces (of constant curvature -1). For example:
A particularly studied family of examples of negatively curved manifolds are given by the symmetric spaces associated to semisimple Lie groups . In this case the Margulis lemma can be given the following, more algebraic formulation which dates back to Hans Zassenhaus . [ 4 ]
Such a neighbourhood Ω {\displaystyle \Omega } is called a Zassenhaus neighbourhood in G {\displaystyle G} . If G {\displaystyle G} is compact this theorem amounts to Jordan's theorem on finite linear groups .
Let M {\displaystyle M} be a Riemannian manifold and ε > 0 {\displaystyle \varepsilon >0} . The thin part of M {\displaystyle M} is the subset of points x ∈ M {\displaystyle x\in M} where the injectivity radius of M {\displaystyle M} at x {\displaystyle x} is less than ε {\displaystyle \varepsilon } , usually denoted M < ε {\displaystyle M_{<\varepsilon }} , and the thick part its complement, usually denoted M ≥ ε {\displaystyle M_{\geq \varepsilon }} . There is a tautological decomposition into a disjoint union M = M < ε ∪ M ≥ ε {\displaystyle M=M_{<\varepsilon }\cup M_{\geq \varepsilon }} .
When M {\displaystyle M} is of negative curvature and ε {\displaystyle \varepsilon } is smaller than the Margulis constant for the universal cover M ~ {\displaystyle {\widetilde {M}}} , the structure of the components of the thin part is very simple. Let us restrict to the case of hyperbolic manifolds of finite volume. Suppose that ε {\displaystyle \varepsilon } is smaller than the Margulis constant for H n {\displaystyle \mathbb {H} ^{n}} and let M {\displaystyle M} be a hyperbolic n {\displaystyle n} -manifold of finite volume. Then its thin part has two sorts of components: [ 5 ]
In particular, a complete finite-volume hyperbolic manifold is always diffeomorphic to the interior of a compact manifold (possibly with empty boundary).
The Margulis lemma is an important tool in the study of manifolds of negative curvature. Besides the thick-thin decomposition some other applications are: | https://en.wikipedia.org/wiki/Margulis_lemma |
Maria Heep-Altiner (born 29 December 1959 in Niederzeuzheim ) is a German mathematician, actuary and university lecturer. [ 1 ]
After graduating from the Prince Johann Ludwig School in Hadamar in 1978, Heep-Altiner studied mathematics and economics at the University of Bonn . In 1989 she earned her doctorate in mathematics on the number theory topic "Period relations for G L 2 ( f ) {\displaystyle GL_{2}(f)} " under Günter Harder and Michael Rapoport . [ 2 ]
She then worked as an actuary for Gerling , before she moved companies in 1994 to Allgemeine Versicherungs-AG. There she became the actuarial manager for property insurance. In 2006, she moved to Talanx , where she was responsible for setting up an internal holding model. [ 1 ]
In 2008, Heep-Altiner returned to academia as a professor at the Institute of Insurance at Cologne university of applied sciences . [ 3 ] There she is responsible for the area of financing in the insurance company.
She is a member of the German Actuarial Society executive board.
In addition, she has co-published various publications on various actuarial topics, in particular on the Solvency II Directive 2009 .
For the following books Heep-Altiner was the main author or significant part of the writing team: | https://en.wikipedia.org/wiki/Maria_Heep-Altiner |
Maria Ibáñez Sabaté is a Spanish materials scientist and Professor at the Institute of Science and Technology Austria . Her research considers functional nanomaterials for next generation technologies. She was awarded the ETH Zurich Ružička Prize in 2017.
Ibáñez studied physics at the University of Barcelona . [ 1 ] She remained there for her doctoral research, where she developed synthesis strategies for colloidal nanoparticles . Her research originally considered materials for photovoltaics, but she became increasingly interested in thermoelectric materials. [ 2 ] During her doctoral research she completed placements at the French Alternative Energies and Atomic Energy Commission , University of Chicago , California Institute of Technology , Cornell University and Northwestern . Her doctoral research was awarded the Extraordinary Award, the University of Barcelona 's highest accolade. [ 2 ] After earning her doctorate she joined ETH Zurich , where she worked with Maksym Kovalenko .
In 2017 Ibáñez was awarded the Ružička Prize for her work on developing new thermoelectric materials. [ 3 ] [ 4 ] She joined the Institute of Science and Technology Austria as an assistant professor in 2018. [ 5 ] She was promoted to the Verbund Professor for Energy Sciences in 2022. [ 6 ]
Her research considers nanocrystals that can be used as building blocks to engineer metamaterials. [ 6 ] She is interested in the development of solution processed thermoelectric materials [ 7 ] with high Seebeck coefficients , electrical conductivities and thermal conductivities. [ 8 ]
Ibáñez is married with two sons. [ 1 ] | https://en.wikipedia.org/wiki/Maria_Ibáñez |
The Maria Mitchell Association is a private non-profit organization on the island of Nantucket off the coast of Massachusetts . The association owns the Maria Mitchell Observatory , a second observatory (the Loines Observatory), a Natural History Museum, the Maria Mitchell Aquarium at Nantucket Harbor, a history museum that is the birthplace of Maria Mitchell , and a Science Library. Staff members of the Maria Mitchell Association conduct research into topics as varied as astrophysics and the American burying beetle , [ 1 ] [ 2 ] [ 3 ] [ 4 ] [ 5 ] amongst other scientific topics. The properties offer a variety of science and history-related programming and are on the National Register of Historic Places , along with the rest of the island.
The Maria Mitchell Association's buildings are located in various areas on the island [ 6 ] including four that are adjacent to each other on the hill in Natucket town. [ 7 ] These include the Historic Mitchell House located at 1 Vestal Street. It preserves the birthplace of Maria Mitchell, and contains many heirlooms of Maria Mitchell and her family. The Science Library located at 2 Vestal Street houses archives and special collections. The Natural Science Museum, at the corner of Milk and Vestal Streets, has several rooms of permanent and temporary exhibits, as well as a shop with books and gifts. The main Vestal Street Observatory, at 3 Vestal Street, includes the offices of the two working astronomers and has a few exhibits such as Maria Mitchell's famed telescope . The Loines Observatory at 59 Milk Street is used primarily for research and on clear nights offers viewings to the public. [ 7 ] An aquarium and shop is located at 28 Washington Street, down the hill at Nantucket Harbor.
Admission is charged for the public to visit each site, [ 7 ] for programs, and for membership. A discounted special ticket is available during the summer for sale to the public to see the House, Museum, Vestal Observatory, and Aquarium for one price. Tours are offered every day during the summer at 11:00 a.m.
The Historic Mitchell House preserves the birthplace of Maria Mitchell. [ 8 ] [ 9 ] It was built in 1790, and occupied by the Mitchell family from 1818, the year of Maria Mitchell's birth. [ 8 ] [ 9 ] The House contains many artifacts of Maria Mitchell and her family, including a tall-case clock and one of her telescopes. [ 8 ] [ 9 ]
The research library includes Mitchell's papers, as well as other historical and scientific material. The house remains very much in its original condition with original decorative paint. Guided tours are provided to the public in-season and children's and adult history classes and historic preservation workshops are offered. The research library includes Mitchell's personal and work related papers, her personal library, the papers and libraries of her family, and the special collection library which includes rare books concerning astronomy, the natural sciences, and Nantucket, some dating back to the 1600s. The archives and special collections are open by appointment only for research purposes.
The Natural Science Museum is across the street from Mitchell House. It showcases displays of animals such as snakes, frogs, and turtles. Furthermore, the museum features a gift shop and various displays related to natural science. The building containing the museum has three floors, of which only the first floor is accessible to the public.
See main article: Maria Mitchell Aquarium
The MMA Aquarium, also known as the Nantucket Aquarium, is on the site of the historic ticket office of the former Nantucket Railroad at 28 Washington Street. [ 10 ] [ 11 ] It is located at directly on the shoreline of the Nantucket Harbor, [ 10 ] which empties out into the Nantucket Sound . Specimens are primarily drawn from the waters around Nantucket, and are released back to those waters at the end of each summer. [ 10 ] [ 11 ] Because the Gulf Stream passes by the Atlantic Ocean side of the island, some tropical fish are frequently on exhibit. [ 10 ] The Aquarium offers programs, including a " feeding frenzy ". [ 10 ]
Loines Observatory was built in 1968 and 1998, the two domes of this facility house a refurbished antique 8-inch Clark telescope and a new 24-inch research telescope. It serves as both an active research observatory and venue for public astronomical programs.
The Vestal Street Observatory has been the site of research, lectures, and other programs. since 1908.
Maria Mitchell Association's observatories are open for regular public tours, programs, lectures, and also host to several special events throughout the year.
The Maria Mitchell Association (MMA) was founded in 1902 to preserve the legacy of Nantucket native, astronomer, naturalist, librarian, and educator, Maria Mitchell . After she discovered a comet in 1847, Mitchell's international fame led to many achievements and awards, including an appointment as the first American Professor of Astronomy at Vassar College . Mitchell died in 1889. [ 12 ]
Each summer, the MMA offers the Summer Discovery Classes Program for children of various ages, and during the school year to the Nantucket Public Schools . [ 13 ] The MMA also offers environmental education programs for families [ 14 ] as well as astronomy and natural science programs for adults. [ 15 ]
The MMA also offers lesson plans , and programs to teachers in local school systems. [ 16 ]
The staff members of the association continue to conduct research into a wide variety of topics from galaxy formation and star clusters, to spiders, molluscs , and the American burying beetle. [ 17 ] They have mentored many aspiring scientists.
The staff of the Maria Mitchell Association currently includes: | https://en.wikipedia.org/wiki/Maria_Mitchell_Association |
Maria de Fátima Montemor is a Portuguese researcher known for her work in coatings for surface protection and functionality, and materials for electrodes for electrochemical energy storage devices. She is a full professor at Instituto Superior Técnico .
Montemor graduated from the Instituto Superior Técnico (Technical University of Lisbon) in 1989. She went on to complete her PhD in chemical engineering in 1995. In 2003 she started her research career at the Department of Chemical Engineering as an assistant researcher. In 2011, Montemor became an assistant professor and reached the position of associate professor in 2015. In 2017 she got her " Agregação " title in Chemical Engineering and started her teaching activity as a full professor in 2018. [ 1 ] As of 2021 she is a full professor Department of Chemical Engineering and a researcher at Centro de Química Estrutural. [ 2 ]
Montemore is known for her work in the field of surface functionalization strategies and development of coatings, including smart self-healing coatings for improved performance of metallic parts (steels, Mg, Zn and Al alloys).
She was awarded the BES innovation prize in 2013, [ 3 ] and the European Corrosion Medal 2019 for her work in coatings for corrosion protection and corrosion science. [ 4 ] In 2021, she received the degree of Doctor " Honoris Causa " from the University of Mons for her work in the domain of coatings for surface protection and functionalization. [ 2 ] | https://en.wikipedia.org/wiki/Maria_de_Fátima_Montemor |
Marie-Louise Dubreil-Jacotin (7 July 1905 – 19 October 1972) was a French mathematician , the second woman to obtain a doctorate in pure mathematics in France, the first woman to become a full professor of mathematics in France, the president of the French Mathematical Society , and an expert on fluid mechanics and abstract algebra .
Marie-Louise Jacotin was the daughter of a lawyer for a French bank, and the grand-daughter (through her mother) of a glassblower from a family of Greek origin. Her mathematics teacher at the lycée was a sister of mathematician Élie Cartan , and after passing the baccalaureate she was allowed (through the intervention of a friend's father, the head of the institution) to continue studying mathematics at the Collège de Chaptal . On her second attempt, she placed second in the entrance examination for the École Normale Supérieure in 1926 (tied with Claude Chevalley ), but by a ministerial decree was moved down to 21st position. After the intervention of Fernand Hauser, the editor of the Journal of the ENS, she was admitted to the school. Her teachers there included Henri Lebesgue and Jacques Hadamard , and she finished her studies in 1929. [ 1 ] [ 2 ] [ 3 ]
With the encouragement of ENS director Ernest Vessiot she traveled to Oslo to work with Vilhelm Bjerknes , under whose influence she became interested in the mathematics of waves and the work of Tullio Levi-Civita in this subject. She returned to Paris in 1930, married another mathematician, Paul Dubreil , and joined him on another tour of the mathematics centers of Germany and Italy, including a visit with Levi-Civita. The Dubreils returned to France again in 1931. [ 1 ] [ 2 ] [ 3 ]
While her husband taught at Lille, Dubreil-Jacotin continued her research, finishing a doctorate in 1934 concerning the existence of infinitely many different waves in ideal liquids , under the supervision of Henri Villat . [ 2 ] [ 3 ] [ 4 ] Before her, the only women to obtain doctorates in mathematics in France were Marie Charpentier in 1931 (also in pure mathematics) and Edmée Chandon in 1930 (in astronomy and geodesy). [ 1 ]
Following her husband, she moved to Nancy , but was unable to obtain a faculty position there herself because that was viewed as nepotism; instead, she became a research assistant at the University of Rennes . She was promoted to a teaching position in 1938, and became an assistant professor at the University of Lyon in 1939, while also continuing to teach at Rennes. In 1943 she became a full professor at the University of Poitiers , the first woman to become a full professor of mathematics in France, and in 1955 she was given a chair there in differential and integral calculus. In 1956 she moved to the University of Paris and after the university split she held a professorship at Pierre and Marie Curie University . [ 2 ] [ 3 ] [ 5 ]
In the 1950s, motivated by the study of averaging operators for turbulence, Dubreil-Jacotin's interests turned towards abstract algebra, and she later performed research in semigroups and graded algebraic structures . She was the author of two textbooks, one on lattice theory and the other on abstract algebra. As well as her technical publications, Jacotin was the author of a work in the history of mathematics , Portraits of women mathematicians . [ 3 ] She was president of the French Mathematical Society for 1952. [ 6 ]
Rue Marie-Louise-Dubreil-Jacotin, a street in the 13th arrondissement of Paris within Paris Diderot University , is named after her, [ 1 ] and the University of Poitiers also has a street with the same name. [ 7 ] In semigroup theory, the Dubreil-Jacotin semigroups are also named after her, [ 8 ] as is the Dubreil-Jacotin–Long equation, "the standard model for internal gravity waves " in fluid mechanics . [ 9 ] | https://en.wikipedia.org/wiki/Marie-Louise_Dubreil-Jacotin |
Marie Françoise "Fanny" Bernard (née Martin ) (16 September 1819 – 9 October 1901) was a French anti-vivisection campaigner and creator of an anti-vivisection society. She was the wife of the pioneer in experimental research in physiology, Claude Bernard . [ 1 ]
Marie Françoise Martin married Claude Bernard on Wednesday 7 May 1845, and it was her dowry from her father, a physician, that allowed him to pursue his studies under François Magendie at the Collège de France in Paris. [ 2 ] They had three children—Jeanne-Henriette, Marie-Claude, and a son who died in infancy. [ 3 ]
Marie Françoise became opposed to her husband's research methods. Magendie, Claude Bernard and his fellow physiologists—men such as Charles Richet in France and Michael Foster in England—were strongly criticized for the vivisection they carried out on animals, particularly dogs. Anti-vivisectionists infiltrated Magendie's lectures in Paris, where he was dissecting dogs without anaesthetic, allegedly shouting " Tais-toi, pauvre bête! " ("Shut up, you poor beast!") while he worked on them. [ 4 ]
She separated from Bernard in 1870. [ 5 ]
At the age of 19 Claude Bernard wrote a play called Arthur de Bretagne , [ 6 ] which was published only after his death. [ 7 ] Marie Françoise and her daughters alleged that it contained a preface that defamed them. They are thought to have sued to have the copies of the play destroyed. However, there was a radio production in 1936, and a second edition appeared in 1943. [ 6 ] [ 8 ]
In 2016, the American author of experimental literature Thalia Field published Experimental Animals: A Reality Fiction , a thoroughly-researched novel in which she writes about Claude Bernard and the nineteenth-century animal rights movement from the point of view of Marie-Françoise "Fanny" Bernard.
This animal rights -related article is a stub . You can help Wikipedia by expanding it .
This biographical article about a French activist is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Marie_Françoise_Bernard |
Marijuana Enforcement Tracking Reporting Compliance (METRC) is a system for tracking state-legalized cannabis in Alaska , California , Colorado , Washington D.C. , Louisiana , Maine , Maryland , Massachusetts , Michigan , Minnesota , Missouri , Montana , Nevada , Ohio , Oklahoma , Oregon , and West Virginia in the United States.
In 2017, a $59 million two-year contract was awarded by the State of California to Florida-based Franwell to create the system and supply RFID tags . [ 1 ] The system was first developed for Colorado in 2011. [ 2 ] As of mid-2017, Franwell's system was in use in California, Colorado, Oregon , Maryland , Alaska , and Michigan . [ 3 ] In June 2017, Franwell withdrew from the Washington State Liquor and Cannabis Board state tracking contract due to the state's preference for vendor(s) who had multiple means of tracking other than proprietary RFID technology, and entry of data concerning non-compliance with regulations, such as production outside of stipulated limits. [ 4 ] [ 5 ]
This Cannabis -related article is a stub . You can help Wikipedia by expanding it .
This software article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Marijuana_Enforcement_Tracking_Reporting_Compliance |
Marinactinospora is a genus in the phylum Actinomycetota ( Bacteria ). It contains a single species, Marinactinospora thermotolerans . The species has a high tolerance for environmental temperatures, up to 55°C. [ 1 ]
The name Marinactinospora derives from the Latin adjective marinus , of or belonging to the sea; Greek noun aktis, aktinos (ἀκτίς, ἀκτῖνος) , a beam; Greek noun spora (σπορά) , a seed, and in biology a spore; Neo-Latin feminine gender noun Marinactinospora , marine and spored ray, referring to marine spore-forming actinomycete. [ 2 ] The specific name derives from the Greek noun thermē (θέρμη) , heat; Latin participle adjective tolerans , tolerating; Neo-Latin participle adjective thermotolerans , able to tolerate a high temperature.) [ 1 ]
The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN) [ 2 ] and National Center for Biotechnology Information (NCBI). [ 3 ]
M. endophytica Liu et al. 2015
M. thermotolerans Tian et al. 2009
M. thermotolerans | https://en.wikipedia.org/wiki/Marinactinospora |
Marine Biology is a peer-reviewed scientific journal covering research on all aspects of marine biology . The journal was established in 1967 and is published monthly by Springer Science+Business Media . The editor-in-chief is Ulrich Sommer ( Helmholtz Centre for Ocean Research ). According to the Journal Citation Reports , the journal has a 2014 impact factor of 2.391. [ 1 ]
This article about a biology journal is a stub . You can help Wikipedia by expanding it .
See tips for writing articles about academic journals . Further suggestions might be found on the article's talk page . | https://en.wikipedia.org/wiki/Marine_Biology_(journal) |
Marine Chemistry is an international peer-reviewed scientific journal for publications in the field of chemistry in the marine environment. [ 1 ] The journal is currently published by Elsevier . Its editor-in-chief is T.S. Bianchi . According to the Journal Citation Reports , Marine Chemistry has a 2020 impact factor of 3.807. [ 2 ]
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The Marine Life Information Network ( MarLIN ) is an information system for marine biodiversity for Great Britain and Ireland . [ 1 ]
MarLIN was established in 1998 by the Marine Biological Association together with the environmental protection agencies and academic institutions in Britain and Ireland. [ 1 ]
The MarLIN data access programme has now become the DASSH Marine Data Archive Cantre. DASSH is built on the existing extensive data and dissemination skills of the Marine Life Information Network (MarLIN), the library and information services of the National Marine Biological Library (NMBL) and the MBA's historical role in marine science.
This oceanography article is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Marine_Life_Information_Network |
The Marine Technology Society ( MTS ) is a professional society that serves an international community of approximately 2,000 ocean engineers, technologists, policy-makers, and educators. The goal of the society, which was founded in 1963, is to promote awareness, understanding, advancement and application of marine technology. [ 1 ] The association is based in Washington, District of Columbia , United States.
The society consists of 29 technical disciplines and presently has 17 sections, including overseas sections in Japan , Korea and Norway . In addition, MTS has 23 student sections at colleges and universities with related fields of study.
The flagship publication of the society is the MTS Journal. The journal is published 4 times annually and primarily features themed issues consisting of invited papers. The journal has a current Scopus Cite Score of 1.6.
MTS sponsors several conferences of note, including the OCEANS Conference (co-sponsosed with IEEE/OES), Underwater Intervention (co-sponsored with ADCI), Dynamic Positioning Conference, biennial Buoy Workshop (co-sponsored with the Office of Naval Research), and the hot-topic workshop series TechSurge.
In 1969 the group held its annual convention in Miami Beach. [ 2 ] The convention was addressed by Spiro Agnew , who was then Vice President of the United States . [ 3 ]
In 1993 the laser line scan, a U.S. Navy photography secret, made its debut at the society sponsored trade show in New Orleans . [ 4 ]
In 2023 the MATE Remotely Operated Vehicle (ROV) Competition joined MTS as a fully integrated program within the Society. For more than 20 years, the MATE ROV Competition has given children, youth, and young adults an inclusive platform to think critically about real-world problems in a way that strengthens communication, builds peer-to-peer community, and inspires entrepreneurship. Since its inauguration, the annual competition has reached more than 20,000 students in 46 regions around the world. [ 5 ]
This article about an organization in the United States is a stub . You can help Wikipedia by expanding it . | https://en.wikipedia.org/wiki/Marine_Technology_Society |
Marine architecture is the design of architectural and engineering structures which support coastal design, near-shore and off-shore or deep-water planning for many projects such as shipyards , ship transport , coastal management or other marine and/or hydroscape activities. These structures include harbors , lighthouses , marinas , oil platforms , offshore drillings , accommodation platforms and offshore wind farms , floating engineering structures and building architectures or civil seascape developments. Floating structures in deep water may use suction caisson for anchoring . [ 1 ] [ 2 ] [ 3 ] [ 4 ] [ 5 ] | https://en.wikipedia.org/wiki/Marine_architecture |
Marine biogeochemical cycles are biogeochemical cycles that occur within marine environments , that is, in the saltwater of seas or oceans or the brackish water of coastal estuaries . These biogeochemical cycles are the pathways chemical substances and elements move through within the marine environment. In addition, substances and elements can be imported into or exported from the marine environment. These imports and exports can occur as exchanges with the atmosphere above, the ocean floor below, or as runoff from the land.
There are biogeochemical cycles for the elements calcium , carbon , hydrogen , mercury , nitrogen , oxygen , phosphorus , selenium , and sulfur ; molecular cycles for water and silica ; macroscopic cycles such as the rock cycle ; as well as human-induced cycles for synthetic compounds such as polychlorinated biphenyl (PCB). In some cycles there are reservoirs where a substance can be stored for a long time. The cycling of these elements is interconnected.
Marine organisms , and particularly marine microorganisms are crucial for the functioning of many of these cycles. The forces driving biogeochemical cycles include metabolic processes within organisms, geological processes involving the Earth's mantle, as well as chemical reactions among the substances themselves, which is why these are called biogeochemical cycles. While chemical substances can be broken down and recombined, the chemical elements themselves can be neither created nor destroyed by these forces, so apart from some losses to and gains from outer space, elements are recycled or stored (sequestered) somewhere on or within the planet.
Energy flows directionally through ecosystems, entering as sunlight (or inorganic molecules for chemoautotrophs) and leaving as heat during the many transfers between trophic levels. However, the matter that makes up living organisms is conserved and recycled. The six most common elements associated with organic molecules—carbon, nitrogen, hydrogen, oxygen, phosphorus, and sulfur—take a variety of chemical forms and may exist for long periods in the atmosphere, on land, in water, or beneath the Earth's surface. Geologic processes, such as weathering, erosion, water drainage, and the subduction of the continental plates, all play a role in this recycling of materials. Because geology and chemistry have major roles in the study of this process, the recycling of inorganic matter between living organisms and their environment is called a biogeochemical cycle. [ 1 ]
The six aforementioned elements are used by organisms in a variety of ways. Hydrogen and oxygen are found in water and organic molecules, both of which are essential to life. Carbon is found in all organic molecules, whereas nitrogen is an important component of nucleic acids and proteins. Phosphorus is used to make nucleic acids and the phospholipids that comprise biological membranes. Sulfur is critical to the three-dimensional shape of proteins. The cycling of these elements is interconnected. For example, the movement of water is critical for leaching sulfur and phosphorus into rivers which can then flow into oceans. Minerals cycle through the biosphere between the biotic and abiotic components and from one organism to another. [ 2 ]
Water is the medium of the oceans, the medium which carries all the substances and elements involved in the marine biogeochemical cycles.
Water as found in nature almost always includes dissolved substances, so water has been described as the "universal solvent" for its ability to dissolve so many substances. [ 3 ] [ 4 ] This ability allows it to be the " solvent of life" [ 5 ] Water is also the only common substance that exists as solid , liquid, and gas in normal terrestrial conditions. [ 6 ] Since liquid water flows, ocean waters cycle and flow in currents around the world. Since water easily changes phase, it can be carried into the atmosphere as water vapour or frozen as an iceberg. It can then precipitate or melt to become liquid water again. All marine life is immersed in water, the matrix and womb of life itself. [ 7 ] Water can be broken down into its constituent hydrogen and oxygen by metabolic or abiotic processes, and later recombined to become water again.
While the water cycle is itself a biogeochemical cycle , flow of water over and beneath the Earth is a key component of the cycling of other biogeochemicals. [ 8 ] Runoff is responsible for almost all of the transport of eroded sediment and phosphorus from land to waterbodies . [ 9 ] Cultural eutrophication of lakes is primarily due to phosphorus, applied in excess to agricultural fields in fertilizers , and then transported overland and down rivers. Both runoff and groundwater flow play significant roles in transporting nitrogen from the land to waterbodies. [ 10 ] The dead zone at the outlet of the Mississippi River is a consequence of nitrates from fertilizer being carried off agricultural fields and funnelled down the river system to the Gulf of Mexico . Runoff also plays a part in the carbon cycle , again through the transport of eroded rock and soil. [ 11 ]
Ocean salinity is derived mainly from the weathering of rocks and the transport of dissolved salts from the land, with lesser contributions from hydrothermal vents in the seafloor. [ 12 ] Evaporation of ocean water and formation of sea ice further increase the salinity of the ocean. However these processes which increase salinity are continually counterbalanced by processes that decrease salinity, such as the continuous input of fresh water from rivers, precipitation of rain and snow, and the melting of ice. [ 13 ] The two most prevalent ions in seawater are chloride and sodium. Together, they make up around 85 per cent of all dissolved ions in the ocean. Magnesium and sulfate ions make up most of the rest. Salinity varies with temperature, evaporation, and precipitation. It is generally low at the equator and poles, and high at mid-latitudes. [ 12 ]
A stream of airborne microorganisms circles the planet above weather systems but below commercial air lanes. [ 16 ] Some peripatetic microorganisms are swept up from terrestrial dust storms, but most originate from marine microorganisms in sea spray . In 2018, scientists reported that hundreds of millions of viruses and tens of millions of bacteria are deposited daily on every square meter around the planet. [ 17 ] [ 18 ] This is another example of water facilitating the transport of organic material over great distances, in this case in the form of live microorganisms.
Dissolved salt does not evaporate back into the atmosphere like water, but it does form sea salt aerosols in sea spray . Many physical processes over ocean surface generate sea salt aerosols. One common cause is the bursting of air bubbles , which are entrained by the wind stress during the whitecap formation. Another is tearing of drops from wave tops. [ 19 ] The total sea salt flux from the ocean to the atmosphere is about 3300 Tg (3.3 billion tonnes) per year. [ 20 ]
Solar radiation affects the oceans: warm water from the Equator tends to circulate toward the poles , while cold polar water heads towards the Equator. The surface currents are initially dictated by surface wind conditions. The trade winds blow westward in the tropics, [ 22 ] and the westerlies blow eastward at mid-latitudes. [ 23 ] This wind pattern applies a stress to the subtropical ocean surface with negative curl across the Northern Hemisphere , [ 24 ] and the reverse across the Southern Hemisphere . The resulting Sverdrup transport is equatorward. [ 25 ] Because of conservation of potential vorticity caused by the poleward-moving winds on the subtropical ridge 's western periphery and the increased relative vorticity of poleward moving water, transport is balanced by a narrow, accelerating poleward current, which flows along the western boundary of the ocean basin, outweighing the effects of friction with the cold western boundary current which originates from high latitudes. [ 26 ] The overall process, known as western intensification , causes currents on the western boundary of an ocean basin to be stronger than those on the eastern boundary. [ 27 ]
As it travels poleward, warm water transported by strong warm water current undergoes evaporative cooling. The cooling is wind driven: wind moving over water cools the water and also causes evaporation , leaving a saltier brine. In this process, the water becomes saltier and denser. and decreases in temperature. Once sea ice forms, salts are left out of the ice, a process known as brine exclusion. [ 28 ] These two processes produce water that is denser and colder. The water across the northern Atlantic Ocean becomes so dense that it begins to sink down through less salty and less dense water. This downdraft of heavy, cold and dense water becomes a part of the North Atlantic Deep Water , a southgoing stream. [ 29 ]
Winds drive ocean currents in the upper 100 meters of the ocean's surface. However, ocean currents also flow thousands of meters below the surface. These deep-ocean currents are driven by differences in the water's density, which is controlled by temperature (thermo) and salinity (haline). This process is known as thermohaline circulation. In the Earth's polar regions ocean water gets very cold, forming sea ice. As a consequence the surrounding seawater gets saltier, because when sea ice forms, the salt is left behind. As the seawater gets saltier, its density increases, and it starts to sink. Surface water is pulled in to replace the sinking water, which in turn eventually becomes cold and salty enough to sink. This initiates the deep-ocean currents driving the global conveyor belt. [ 30 ]
Thermohaline circulation drives a global-scale system of currents called the “global conveyor belt.” The conveyor belt begins on the surface of the ocean near the pole in the North Atlantic. Here, the water is chilled by Arctic temperatures. It also gets saltier because when sea ice forms, the salt does not freeze and is left behind in the surrounding water. The cold water is now more dense, due to the added salts, and sinks toward the ocean bottom. Surface water moves in to replace the sinking water, thus creating a current. This deep water moves south, between the continents, past the equator, and down to the ends of Africa and South America. The current travels around the edge of Antarctica, where the water cools and sinks again, as it does in the North Atlantic. Thus, the conveyor belt gets "recharged." As it moves around Antarctica, two sections split off the conveyor and turn northward. One section moves into the Indian Ocean, the other into the Pacific Ocean. These two sections that split off warm up and become less dense as they travel northward toward the equator, so that they rise to the surface (upwelling). They then loop back southward and westward to the South Atlantic, eventually returning to the North Atlantic, where the cycle begins again. The conveyor belt moves at much slower speeds (a few centimeters per second) than wind-driven or tidal currents (tens to hundreds of centimeters per second). It is estimated that any given cubic meter of water takes about 1,000 years to complete the journey along the global conveyor belt. In addition, the conveyor moves an immense volume of water—more than 100 times the flow of the Amazon River (Ross, 1995). The conveyor belt is also a vital component of the global ocean nutrient and carbon dioxide cycles. Warm surface waters are depleted of nutrients and carbon dioxide, but they are enriched again as they travel through the conveyor belt as deep or bottom layers. The base of the world's food chain depends on the cool, nutrient-rich waters that support the growth of algae and seaweed. [ 31 ]
The global average residence time of a water molecule in the ocean is about 3,200 years. By comparison the average residence time in the atmosphere is about nine days. If it is frozen in the Antarctic or drawn into deep groundwater it can be sequestered for ten thousand years. [ 32 ] [ 33 ]
Box models are widely used to model biogeochemical systems. [ 64 ] Box models are simplified versions of complex systems, reducing them to boxes (or storage reservoirs ) for chemical materials, linked by material fluxes (flows). Simple box models have a small number of boxes with properties, such as volume, that do not change with time. The boxes are assumed to behave as if they were mixed homogeneously. [ 63 ] These models are often used to derive analytical formulas describing the dynamics and steady-state abundance of the chemical species involved.
The diagram at the right shows a basic one-box model. The reservoir contains the amount of material M under consideration, as defined by chemical, physical or biological properties. The source Q is the flux of material into the reservoir, and the sink S is the flux of material out of the reservoir. The budget is the check and balance of the sources and sinks affecting material turnover in a reservoir. The reservoir is in a steady state if Q = S , that is, if the sources balance the sinks and there is no change over time. [ 63 ]
Global biogeochemical box models usually measure: — reservoir masses in petagrams (Pg) — flow fluxes in petagrams per year (Pg yr −1 ) Diagrams in this article mostly use these units ________________________________________________ one petagram = 10 15 grams = one gigatonne = one billion (10 9 ) tonnes
The turnover time (also called the renewal time or exit age) is the average time material spends resident in the reservoir. If the reservoir is in a steady state, this is the same as the time it takes to fill or drain the reservoir. Thus, if τ is the turnover time, then τ = M/S. [ 63 ] The equation describing the rate of change of content in a reservoir is
When two or more reservoirs are connected, the material can be regarded as cycling between the reservoirs, and there can be predictable patterns to the cyclic flow. [ 63 ] More complex multibox models are usually solved using numerical techniques.
The diagram above shows a simplified budget of ocean carbon flows. It is composed of three simple interconnected box models, one for the euphotic zone , one for the ocean interior or dark ocean, and one for ocean sediments . In the euphotic zone, net phytoplankton production is about 50 Pg C each year. About 10 Pg is exported to the ocean interior while the other 40 Pg is respired. Organic carbon degradation occurs as particles ( marine snow ) settle through the ocean interior. Only 2 Pg eventually arrives at the seafloor, while the other 8 Pg is respired in the dark ocean. In sediments, the time scale available for degradation increases by orders of magnitude with the result that 90% of the organic carbon delivered is degraded and only 0.2 Pg C yr −1 is eventually buried and transferred from the biosphere to the geosphere. [ 65 ]
The biological pump , in its simplest form, is the ocean's biologically driven sequestration of carbon from the atmosphere to the ocean interior and seafloor sediments . [ 73 ] It is the part of the oceanic carbon cycle responsible for the cycling of organic matter formed mainly by phytoplankton during photosynthesis (soft-tissue pump), as well as the cycling of calcium carbonate (CaCO 3 ) formed into shells by certain organisms such as plankton and mollusks (carbonate pump). [ 74 ]
The biological pump can be divided into three distinct phases, [ 75 ] the first of which is the production of fixed carbon by planktonic phototrophs in the euphotic (sunlit) surface region of the ocean. In these surface waters, phytoplankton use carbon dioxide (CO 2 ), nitrogen (N), phosphorus (P), and other trace elements ( barium , iron , zinc , etc.) during photosynthesis to make carbohydrates , lipids , and proteins . Some plankton, (e.g. coccolithophores and foraminifera ) combine calcium (Ca) and dissolved carbonates ( carbonic acid and bicarbonate ) to form a calcium carbonate (CaCO 3 ) protective coating.
Once this carbon is fixed into soft or hard tissue, the organisms either stay in the euphotic zone to be recycled as part of the regenerative nutrient cycle or once they die, continue to the second phase of the biological pump and begin to sink to the ocean floor. The sinking particles will often form aggregates as they sink, greatly increasing the sinking rate. It is this aggregation that gives particles a better chance of escaping predation and decomposition in the water column and eventually make it to the sea floor.
The fixed carbon that is either decomposed by bacteria on the way down or once on the sea floor then enters the final phase of the pump and is remineralized to be used again in primary production . The particles that escape these processes entirely are sequestered in the sediment and may remain there for millions of years. It is this sequestered carbon that is responsible for ultimately lowering atmospheric CO 2 .
The marine carbon cycle is composed of processes that exchange carbon between various pools within the ocean as well as between the atmosphere, Earth interior, and the seafloor . The carbon cycle is a result of many interacting forces across multiple time and space scales that circulates carbon around the planet, ensuring that carbon is available globally. The Oceanic carbon cycle is a central process to the global carbon cycle and contains both inorganic carbon (carbon not associated with a living thing, such as carbon dioxide) and organic carbon (carbon that is, or has been, incorporated into a living thing). Part of the marine carbon cycle transforms carbon between non-living and living matter.
Three main processes (or pumps) that make up the marine carbon cycle bring atmospheric carbon dioxide (CO 2 ) into the ocean interior and distribute it through the oceans. These three pumps are: (1) the solubility pump, (2) the carbonate pump, and (3) the biological pump. The total active pool of carbon at the Earth's surface for durations of less than 10,000 years is roughly 40,000 gigatons C (Gt C, a gigaton is one billion tons, or the weight of approximately 6 million blue whales ), and about 95% (~38,000 Gt C) is stored in the ocean, mostly as dissolved inorganic carbon. [ 34 ] [ 35 ] The speciation of dissolved inorganic carbon in the marine carbon cycle is a primary controller of acid-base chemistry in the oceans.
The nitrogen cycle is as important in the ocean as it is on land. While the overall cycle is similar in both cases, there are different players and modes of transfer for nitrogen in the ocean. [ 79 ] Nitrogen enters the ocean through precipitation, runoff, or as N 2 from the atmosphere. Nitrogen cannot be utilized by phytoplankton as N 2 so it must undergo nitrogen fixation which is performed predominantly by cyanobacteria . [ 80 ] Without supplies of fixed nitrogen entering the marine cycle, the fixed nitrogen would be used up in about 2000 years. [ 81 ] Phytoplankton need nitrogen in biologically available forms for the initial synthesis of organic matter. Ammonia and urea are released into the water by excretion from plankton. Nitrogen sources are removed from the euphotic zone by the downward movement of the organic matter. This can occur from sinking of phytoplankton, vertical mixing, or sinking of waste of vertical migrators. The sinking results in ammonia being introduced at lower depths below the euphotic zone. Bacteria are able to convert ammonia to nitrite and nitrate but they are inhibited by light so this must occur below the euphotic zone. [ 80 ] Ammonification or mineralization is performed by bacteria to convert organic nitrogen to ammonia. Nitrification can then occur to convert the ammonium to nitrite and nitrate. [ 82 ] Nitrate can be returned to the euphotic zone by vertical mixing and upwelling where it can be taken up by phytoplankton to continue the cycle. N 2 can be returned to the atmosphere through denitrification .
Ammonium is thought to be the preferred source of fixed nitrogen for phytoplankton because its assimilation does not involve a redox reaction and therefore requires little energy. Nitrate requires a redox reaction for assimilation but is more abundant so most phytoplankton have adapted to have the enzymes necessary to undertake this reduction ( nitrate reductase ). There are a few notable and well-known exceptions that include most Prochlorococcus and some Synechococcus that can only take up nitrogen as ammonium. [ 81 ]
Phosphorus is an essential nutrient for plants and animals. Phosphorus is a limiting nutrient for aquatic organisms. Phosphorus forms parts of important life-sustaining molecules that are very common in the biosphere. Phosphorus does enter the atmosphere in very small amounts when the dust is dissolved in rainwater and seaspray but remains mostly on land and in rock and soil minerals. Eighty per cent of the mined phosphorus is used to make fertilizers. Phosphates from fertilizers, sewage and detergents can cause pollution in lakes and streams. Over-enrichment of phosphate in both fresh and inshore marine waters can lead to massive algae blooms which, when they die and decay leads to eutrophication of freshwaters only. Recent research suggests that the predominant pollutant responsible for algal blooms in saltwater estuaries and coastal marine habitats is nitrogen. [ 83 ]
Phosphorus occurs most abundantly in nature as part of the orthophosphate ion (PO 4 ) 3− , consisting of a P atom and 4 oxygen atoms. On land most phosphorus is found in rocks and minerals. Phosphorus-rich deposits have generally formed in the ocean or from guano, and over time, geologic processes bring ocean sediments to land. Weathering of rocks and minerals release phosphorus in a soluble form where it is taken up by plants, and it is transformed into organic compounds. The plants may then be consumed by herbivores and the phosphorus is either incorporated into their tissues or excreted. After death, the animal or plant decays, and phosphorus is returned to the soil where a large part of the phosphorus is transformed into insoluble compounds. Runoff may carry a small part of the phosphorus back to the ocean . [ 84 ]
A nutrient cycle is the movement and exchange of organic and inorganic matter back into the production of matter. The process is regulated by the pathways available in marine food webs , which ultimately decompose organic matter back into inorganic nutrients. Nutrient cycles occur within ecosystems. Energy flow always follows a unidirectional and noncyclic path, whereas the movement of mineral nutrients is cyclic. Mineral cycles include the carbon cycle , oxygen cycle , nitrogen cycle , phosphorus cycle and sulfur cycle among others that continually recycle along with other mineral nutrients into productive ecological nutrition.
There is considerable overlap between the terms for the biogeochemical cycle and nutrient cycle. Some textbooks integrate the two and seem to treat them as synonymous terms. [ 86 ] However, the terms often appear independently. Nutrient cycle is more often used in direct reference to the idea of an intra-system cycle, where an ecosystem functions as a unit. From a practical point, it does not make sense to assess a terrestrial ecosystem by considering the full column of air above it as well as the great depths of Earth below it. While an ecosystem often has no clear boundary, as a working model it is practical to consider the functional community where the bulk of matter and energy transfer occurs. [ 87 ] Nutrient cycling occurs in ecosystems that participate in the "larger biogeochemical cycles of the earth through a system of inputs and outputs." [ 87 ] : 425
Nutrients dissolved in seawater are essential for the survival of marine life. Nitrogen and phosphorus are particularly important. They are regarded as limiting nutrients in many marine environments, because primary producers, like algae and marine plants, cannot grow without them. They are critical for stimulating primary production by phytoplankton . Other important nutrients are silicon, iron, and zinc. [ 88 ]
The process of cycling nutrients in the sea starts with biological pumping , when nutrients are extracted from surface waters by phytoplankton to become part of their organic makeup. Phytoplankton are either eaten by other organisms, or eventually die and drift down as marine snow . There they decay and return to the dissolved state, but at greater ocean depths. The fertility of the oceans depends on the abundance of the nutrients, and is measured by the primary production , which is the rate of fixation of carbon per unit of water per unit time. "Primary production is often mapped by satellites using the distribution of chlorophyll, which is a pigment produced by plants that absorbs energy during photosynthesis. The distribution of chlorophyll is shown in the figure above. You can see the highest abundance close to the coastlines where nutrients from the land are fed in by rivers. The other location where chlorophyll levels are high is in upwelling zones where nutrients are brought to the surface ocean from depth by the upwelling process..." [ 88 ]
"Another critical element for the health of the oceans is the dissolved oxygen content. Oxygen in the surface ocean is continuously added across the air-sea interface as well as by photosynthesis; it is used up in respiration by marine organisms and during the decay or oxidation of organic material that rains down in the ocean and is deposited on the ocean bottom. Most organisms require oxygen, thus its depletion has adverse effects for marine populations. Temperature also affects oxygen levels as warm waters can hold less dissolved oxygen than cold waters. This relationship will have major implications for future oceans, as we will see... The final seawater property we will consider is the content of dissolved CO 2 . CO 2 is nearly opposite to oxygen in many chemical and biological processes; it is used up by plankton during photosynthesis and replenished during respiration as well as during the oxidation of organic matter. As we will see later, CO 2 content has importance for the study of deep-water aging." [ 88 ]
Sulfate reduction in the seabed is strongly focused toward near-surface sediments with high depositional rates along the ocean margins. The benthic marine sulfur cycle is therefore sensitive to anthropogenic influence, such as ocean warming and increased nutrient loading of coastal seas. This stimulates photosynthetic productivity and results in enhanced export of organic matter to the seafloor, often combined with low oxygen concentration in the bottom water (Rabalais et al., 2014; Breitburg et al., 2018). The biogeochemical zonation is thereby compressed toward the sediment surface, and the balance of organic matter mineralization is shifted from oxic and suboxic processes toward sulfate reduction and methanogenesis (Middelburg and Levin, 2009). [ 89 ]
The sulfur cycle in marine environments has been well-studied via the tool of sulfur isotope systematics expressed as δ 34 S. The modern global oceans have sulfur storage of 1.3 × 10 21 g, [ 90 ] mainly occurring as sulfate with the δ 34 S value of +21‰. [ 91 ] The overall input flux is 1.0 × 10 14 g/year with the sulfur isotope composition of ~3‰. [ 91 ] Riverine sulfate derived from the terrestrial weathering of sulfide minerals (δ 34 S = +6‰) is the primary input of sulfur to the oceans. Other sources are metamorphic and volcanic degassing and hydrothermal activity (δ 34 S = 0‰), which release reduced sulfur species (e.g., H 2 S and S 0 ). There are two major outputs of sulfur from the oceans. The first sink is the burial of sulfate either as marine evaporites (e.g., gypsum) or carbonate-associated sulfate (CAS), which accounts for 6 × 10 13 g/year (δ 34 S = +21‰). The second sulfur sink is pyrite burial in shelf sediments or deep seafloor sediments (4 × 10 13 g/year; δ 34 S = -20‰). [ 92 ] The total marine sulfur output flux is 1.0 × 10 14 g/year which matches the input fluxes, implying the modern marine sulfur budget is at steady state. [ 91 ] The residence time of sulfur in modern global oceans is 13,000,000 years. [ 93 ]
In modern oceans, Hydrogenovibrio crunogenus , Halothiobacillus , and Beggiatoa are primary sulfur oxidizing bacteria, [ 94 ] [ 95 ] and form chemosynthetic symbioses with animal hosts. [ 96 ] The host provides metabolic substrates (e.g., CO 2 , O 2 , H 2 O) to the symbiont while the symbiont generates organic carbon for sustaining the metabolic activities of the host. The produced sulfate usually combines with the leached calcium ions to form gypsum , which can form widespread deposits on near mid-ocean spreading centers. [ 97 ]
Hydrothermal vents emit hydrogen sulfide that support the carbon fixation of chemolithotrophic bacteria that oxidize hydrogen sulfide with oxygen to produce elemental sulfur or sulfate. [ 94 ]
The iron cycle (Fe) is the biogeochemical cycle of iron through the atmosphere , hydrosphere , biosphere and lithosphere . While Fe is highly abundant in the Earth's crust, [ 102 ] it is less common in oxygenated surface waters. Iron is a key micronutrient in primary productivity , [ 48 ] and a limiting nutrient in the Southern ocean, eastern equatorial Pacific, and the subarctic Pacific referred to as High-Nutrient, Low-Chlorophyll (HNLC) regions of the ocean. [ 49 ]
Iron in the ocean cycles between plankton, aggregated particulates (non-bioavailable iron), and dissolved (bioavailable iron), and becomes sediments through burial. [ 98 ] [ 103 ] [ 104 ] Hydrothermal vents release ferrous iron to the ocean [ 105 ] in addition to oceanic iron inputs from land sources. Iron reaches the atmosphere through volcanism, [ 106 ] aeolian wind, [ 107 ] and some via combustion by humans. In the Anthropocene , iron is removed from mines in the crust and a portion re-deposited in waste repositories. [ 101 ] [ 104 ]
Iron is an essential micronutrient for almost every life form. It is a key component of hemoglobin, important to nitrogen fixation as part of the Nitrogenase enzyme family, and as part of the iron-sulfur core of ferredoxin it facilitates electron transport in chloroplasts, eukaryotic mitochondria, and bacteria. Due to the high reactivity of Fe 2+ with oxygen and low solubility of Fe 3+ , iron is a limiting nutrient in most regions of the world.
The calcium cycle is a transfer of calcium between dissolved and solid phases. There is a continuous supply of calcium ions into waterways from rocks , organisms , and soils . [ 53 ] [ 110 ] Calcium ions are consumed and removed from aqueous environments as they react to form insoluble structures such as calcium carbonate and calcium silicate, [ 53 ] [ 111 ] which can deposit to form sediments or the exoskeletons of organisms. [ 56 ] Calcium ions can also be utilized biologically , as calcium is essential to biological functions such as the production of bones and teeth or cellular function. [ 57 ] [ 58 ] The calcium cycle is a common thread between terrestrial, marine, geological, and biological processes. [ 59 ] Calcium moves through these different media as it cycles throughout the Earth. The marine calcium cycle is affected by changing atmospheric carbon dioxide due to ocean acidification . [ 56 ]
Biogenic calcium carbonate is formed when marine organisms, such as coccolithophores , corals , pteropods , and other mollusks transform calcium ions and bicarbonate into shells and exoskeletons of calcite or aragonite , both forms of calcium carbonate. [ 56 ] This is the dominant sink for dissolved calcium in the ocean. [ 59 ] Dead organisms sink to the bottom of the ocean, depositing layers of shell which over time cement to form limestone . This is the origin of both marine and terrestrial limestone. [ 56 ]
Calcium precipitates into calcium carbonate according to the following equation:
Ca 2+ + 2HCO 3 − → CO 2 + H 2 O + CaCO 3 [ 110 ]
The relationship between dissolved calcium and calcium carbonate is affected greatly by the levels of carbon dioxide (CO 2 ) in the atmosphere.
Increased carbon dioxide leads to more bicarbonate in the ocean according to the following equation:
CO 2 + CO 3 2− + H 2 O → 2HCO 3 − [ 112 ]
With its close relation to the carbon cycle and the effects of greenhouse gasses, both calcium and carbon cycles are predicted to change in the coming years. [ 115 ] Tracking calcium isotopes enables the prediction of environmental changes, with many sources suggesting increasing temperatures in both the atmosphere and marine environment. As a result, this will drastically alter the breakdown of rock, the pH of oceans and waterways and thus calcium sedimentation, hosting an array of implications on the calcium cycle.
Due to the complex interactions of calcium with many facets of life, the effects of altered environmental conditions are unlikely to be known until they occur. Predictions can however be tentatively made, based upon evidence-based research. Increasing carbon dioxide levels and decreasing ocean pH will alter calcium solubility, preventing corals and shelled organisms from developing their calcium-based exoskeletons, thus making them vulnerable or unable to survive. [ 116 ] [ 117 ]
Most biological production of biogenic silica in the ocean is driven by diatoms , with further contributions from radiolarians . These microorganisms extract dissolved silicic acid from surface waters during growth, and return this by recycling throughout the water column after they die. Inputs of silicon to the ocean from above arrive via rivers and aeolian dust , while those from below include seafloor sediment recycling, weathering, and hydrothermal activity . [ 118 ]
"Biological activity is a dominant force shaping the chemical structure and evolution of the earth surface environment. The presence of an oxygenated atmosphere-hydrosphere surrounding an otherwise highly reducing solid earth is the most striking consequence of the rise of life on earth. Biological evolution and the functioning of ecosystems, in turn, are to a large degree conditioned by geophysical and geological processes. Understanding the interactions between organisms and their abiotic environment, and the resulting coupled evolution of the biosphere and geosphere is a central theme of research in biogeology. Biogeochemists contribute to this understanding by studying the transformations and transport of chemical substrates and products of biological activity in the environment." [ 119 ]
"Since the Cambrian explosion, mineralized body parts have been secreted in large quantities by biota. Because calcium carbonate, silica and calcium phosphate are the main mineral phases constituting these hard parts, biomineralization plays an important role in the global biogeochemical cycles of carbon, calcium, silicon and phosphorus" [ 119 ]
Deep cycling involves the exchange of materials with the mantle . The deep water cycle involves exchange of water with the mantle, with water carried down by subducting oceanic plates and returning through volcanic activity, distinct from the water cycle process that occurs above and on the surface of Earth. Some of the water makes it all the way to the lower mantle and may even reach the outer core .
In the conventional view of the water cycle (also known as the hydrologic cycle ), water moves between reservoirs in the atmosphere and Earth's surface or near-surface (including the ocean , rivers and lakes , glaciers and polar ice caps , the biosphere and groundwater ). However, in addition to the surface cycle, water also plays an important role in geological processes reaching down into the crust and mantle . Water content in magma determines how explosive a volcanic eruption is; hot water is the main conduit for economically important minerals to concentrate in hydrothermal mineral deposits ; and water plays an important role in the formation and migration of petroleum . [ 120 ] Petroleum is a fossil fuel derived from ancient fossilized organic materials , such as zooplankton and algae . [ 121 ] [ 122 ]
Water is not just present as a separate phase in the ground. Seawater percolates into oceanic crust and hydrates igneous rocks such as olivine and pyroxene , transforming them into hydrous minerals such as serpentines , talc and brucite . [ 123 ] In this form, water is carried down into the mantle. In the upper mantle , heat and pressure dehydrates these minerals, releasing much of it to the overlying mantle wedge , triggering the melting of rock that rises to form volcanic arcs . [ 124 ] However, some of the "nominally anhydrous minerals" that are stable deeper in the mantle can store small concentrations of water in the form of hydroxyl (OH − ), [ 125 ] and because they occupy large volumes of the Earth, they are capable of storing at least as much as the world's oceans. [ 120 ]
The conventional view of the ocean's origin is that it was filled by outgassing from the mantle in the early Archean and the mantle has remained dehydrated ever since. [ 127 ] However, subduction carries water down at a rate that would empty the ocean in 1–2 billion years. Despite this, changes in the global sea level over the past 3–4 billion years have only been a few hundred metres, much smaller than the average ocean depth of 4 kilometres. Thus, the fluxes of water into and out of the mantle are expected to be roughly balanced, and the water content of the mantle steady. Water carried into the mantle eventually returns to the surface in eruptions at mid-ocean ridges and hotspots . [ 128 ] : 646 Estimates of the amount of water in the mantle range from 1 ⁄ 4 to 4 times the water in the ocean. [ 128 ] : 630–634
The deep carbon cycle is the movement of carbon through the Earth's mantle and core .
It forms part of the carbon cycle and is intimately connected to the movement of carbon in the Earth's surface and atmosphere. By returning carbon to the deep Earth, it plays a critical role in maintaining the terrestrial conditions necessary for life to exist. Without it, carbon would accumulate in the atmosphere, reaching extremely high concentrations over long periods of time. [ 129 ]
Aquatic phytoplankton and zooplankton that died and sedimented in large quantities under anoxic conditions millions of years ago began forming petroleum and natural gas as a result of anaerobic decomposition (by contrast, terrestrial plants tended to form coal and methane). Over geological time this organic matter , mixed with mud , became buried under further heavy layers of inorganic sediment. The resulting high temperature and pressure caused the organic matter to chemically alter , first into a waxy material known as kerogen , which is found in oil shales , and then with more heat into liquid and gaseous hydrocarbons in a process known as catagenesis .
Such organisms and their resulting fossil fuels typically have an age of millions of years, and sometimes more than 650 million years, [ 130 ] the energy released in combustion is still photosynthetic in origin. [ 131 ]
Such as trace minerals, micronutrients, human-induced cycles for synthetic compounds such as polychlorinated biphenyl (PCB). | https://en.wikipedia.org/wiki/Marine_biogeochemical_cycles |
Marine biology is the scientific study of the biology of marine life , organisms that inhabit the sea . Given that in biology many phyla , families and genera have some species that live in the sea and others that live on land, marine biology classifies species based on the environment rather than on taxonomy .
A large proportion of all life on Earth lives in the ocean. The exact size of this "large proportion" is unknown, since many ocean species are still to be discovered. The ocean is a complex three-dimensional world, [ 1 ] covering approximately 71% of the Earth's surface. The habitats studied in marine biology include everything from the tiny layers of surface water in which organisms and abiotic items may be trapped in surface tension between the ocean and atmosphere, to the depths of the oceanic trenches , sometimes 10,000 meters or more beneath the surface of the ocean.
Specific habitats include estuaries , coral reefs , kelp forests , seagrass meadows , the surrounds of seamounts and thermal vents , tidepools , muddy, sandy and rocky bottoms, and the open ocean ( pelagic ) zone, where solid objects are rare and the surface of the water is the only visible boundary. The organisms studied range from microscopic phytoplankton and zooplankton to huge cetaceans (whales) 25–32 meters (82–105 feet) in length. Marine ecology is the study of how marine organisms interact with each other and the environment.
Marine life is a vast resource, providing food, medicine, and raw materials, in addition to helping to support recreation and tourism all over the world. At a fundamental level, marine life helps determine the very nature of our planet. Marine organisms contribute significantly to the oxygen cycle , and are involved in the regulation of the Earth's climate . [ 2 ] Shorelines are in part shaped and protected by marine life, and some marine organisms even help create new land. [ 3 ]
Many species are economically important to humans, including both finfish and shellfish. It is also becoming understood that the well-being of marine organisms and other organisms are linked in fundamental ways. The human body of knowledge regarding the relationship between life in the sea and important cycles is rapidly growing, with new discoveries being made nearly every day. These cycles include those of matter (such as the carbon cycle ) and of air (such as Earth's respiration , and movement of energy through ecosystems including the ocean). Large areas beneath the ocean surface still remain effectively unexplored.
Marine biology can be contrasted with biological oceanography . Marine life is a field of study both in marine biology and in biological oceanography . Biological oceanography is the study of how organisms affect and are affected by the physics , chemistry , and geology of the oceanographic system . Biological oceanography mostly focuses on the microorganisms within the ocean; looking at how they are affected by their environment and how that affects larger marine creatures and their ecosystem. [ 6 ]
Biological oceanography is similar to marine biology, but it studies ocean life from a different perspective. Biological oceanography takes a bottom up approach in terms of the food web, while marine biology studies the ocean from a top down perspective. Biological oceanography mainly focuses on the ecosystem of the ocean with an emphasis on plankton : their diversity (morphology, nutritional sources, motility, and metabolism); their productivity and how that plays a role in the global carbon cycle; and their distribution (predation and life cycle). [ 6 ] [ 7 ] [ 8 ] Biological oceanography also investigates the role of microbes in food webs, and how humans impact the ecosystems in the oceans. [ 6 ] [ 9 ]
Marine habitats can be divided into coastal and open ocean habitats. Coastal habitats are found in the area that extends from the shoreline to the edge of the continental shelf . Most marine life is found in coastal habitats, even though the shelf area occupies only seven percent of the total ocean area. Open ocean habitats are found in the deep ocean beyond the edge of the continental shelf. Alternatively, marine habitats can be divided into pelagic and demersal habitats. Pelagic habitats are found near the surface or in the open water column , away from the bottom of the ocean and affected by ocean currents , while demersal habitats are near or on the bottom. Marine habitats can be modified by their inhabitants. Some marine organisms, like corals, kelp and sea grasses, are ecosystem engineers which reshape the marine environment to the point where they create further habitat for other organisms.
Intertidal zones , the areas that are close to the shore, are constantly being exposed and covered by the ocean's tides . A huge array of life can be found within this zone. Shore habitats span from the upper intertidal zones to the area where land vegetation takes prominence. It can be underwater anywhere from daily to very infrequently. Many species here are scavengers, living off of sea life that is washed up on the shore. Many land animals also make much use of the shore and intertidal habitats. A subgroup of organisms in this habitat bores and grinds exposed rock through the process of bioerosion .
Estuaries are also near shore and influenced by the tides . An estuary is a partially enclosed coastal body of water with one or more rivers or streams flowing into it and with a free connection to the open sea. [ 10 ] Estuaries form a transition zone between freshwater river environments and saltwater maritime environments. They are subject both to marine influences—such as tides, waves, and the influx of saline water—and to riverine influences—such as flows of fresh water and sediment. The shifting flows of both sea water and fresh water provide high levels of nutrients both in the water column and in sediment, making estuaries among the most productive natural habitats in the world. [ 11 ]
Reefs comprise some of the densest and most diverse habitats in the world. The best-known types of reefs are tropical coral reefs which exist in most tropical waters; however, reefs can also exist in cold water. Reefs are built up by corals and other calcium -depositing animals, usually on top of a rocky outcrop on the ocean floor. Reefs can also grow on other surfaces, which has made it possible to create artificial reefs . Coral reefs also support a huge community of life, including the corals themselves, their symbiotic zooxanthellae , tropical fish and many other organisms.
Much attention in marine biology is focused on coral reefs and the El Niño weather phenomenon. In 1998, coral reefs experienced the most severe mass bleaching events on record, when vast expanses of reefs across the world died because sea surface temperatures rose well above normal. [ 12 ] [ 13 ] Some reefs are recovering, but scientists say that between 50% and 70% of the world's coral reefs are now endangered and predict that global warming could exacerbate this trend. [ 14 ] [ 15 ] [ 16 ] [ 17 ]
The open ocean is relatively unproductive because of a lack of nutrients, yet because it is so vast, in total it produces the most primary productivity. The open ocean is separated into different zones, and the different zones each have different ecologies. [ 19 ] Zones which vary according to their depth include the epipelagic , mesopelagic , bathypelagic , abyssopelagic , and hadopelagic zones. Zones which vary by the amount of light they receive include the photic and aphotic zones . Much of the aphotic zone's energy is supplied by the open ocean in the form of detritus .
The deepest recorded oceanic trench measured to date is the Mariana Trench , near the Philippines , in the Pacific Ocean at 10,924 m (35,840 ft). At such depths, water pressure is extreme and there is no sunlight, but some life still exists. A white flatfish , a shrimp and a jellyfish were seen by the crew of the bathyscaphe Trieste when it dove to the bottom in 1960, which led to scientific debate surrounding the likelihood of bony fish surviving in such deep waters. General scientific consensus has discredited the possible viewing of a flatfish at such depths. [ 20 ] [ 21 ] [ 22 ] [ 23 ]
In general, the deep sea is considered to start at the aphotic zone , the point where sunlight loses its power of transference through the water. [ 24 ] Many life forms that live at these depths have the ability to create their own light known as bio-luminescence . Marine life also flourishes around seamounts that rise from the depths, where fish and other sea life congregate to spawn and feed. Hydrothermal vents along the mid-ocean ridge spreading centers act as oases , as do their opposites, cold seeps . Such places support unique biomes and many new microbes and other lifeforms have been discovered at these locations. There is still much more to learn about the deeper parts of the ocean . [ 25 ]
In biology, many phyla, families and genera have some species that live in the sea and others that live on land. Marine biology classifies species based on their environment rather than their taxonomy. For this reason, marine biology encompasses not only organisms that live only in a marine environment, but also other organisms whose lives revolve around the sea.
As inhabitants of the largest environment on Earth, microbial marine systems drive changes in every global system. Microbes are responsible for virtually all photosynthesis that occurs in the ocean, as well as the cycling of carbon , nitrogen , phosphorus and other nutrients and trace elements. [ 26 ]
Microscopic life undersea is incredibly diverse and still poorly understood. For example, the role of viruses in marine ecosystems is barely being explored even in the beginning of the 21st century. [ 27 ]
The role of phytoplankton is better understood due to their critical position as the most numerous primary producers on Earth. Phytoplankton are categorized into cyanobacteria (also called blue-green algae/bacteria), various types of algae (red, green, brown, and yellow-green), diatoms , dinoflagellates , euglenoids , coccolithophorids , cryptomonads , chrysophytes , chlorophytes , prasinophytes , and silicoflagellates .
Zooplankton tend to be somewhat larger, and not all are microscopic. Many Protozoa are zooplankton, including dinoflagellates, zooflagellates , foraminiferans , and radiolarians . Some of these (such as dinoflagellates) are also phytoplankton; the distinction between plants and animals often breaks down in very small organisms. Other zooplankton include cnidarians , ctenophores , chaetognaths , molluscs , arthropods , urochordates , and annelids such as polychaetes . Many larger animals begin their life as zooplankton before they become large enough to take their familiar forms. Two examples are fish larvae and sea stars (also called starfish ).
Microscopic algae and plants provide important habitats for life, sometimes acting as hiding places for larval forms of larger fish and foraging places for invertebrates.
Algal life is widespread and very diverse under the ocean. Microscopic photosynthetic algae contribute a larger proportion of the world's photosynthetic output than all the terrestrial forests combined. Most of the niche occupied by sub plants on land is actually occupied by macroscopic algae in the ocean, such as Sargassum and kelp , which are commonly known as seaweeds that create kelp forests .
Plants that survive in the sea are often found in shallow waters, such as the seagrasses (examples of which are eelgrass, Zostera , and turtle grass, Thalassia ). These plants have adapted to the high salinity of the ocean environment. The intertidal zone is also a good place to find plant life in the sea, where mangroves or cordgrass or beach grass might grow.
As on land, invertebrates , or animals that lack a backbone, make up a huge portion of all life in the sea. Invertebrate sea life includes Cnidaria such as jellyfish and sea anemones ; Ctenophora ; sea worms including the phyla Platyhelminthes , Nemertea , Annelida , Sipuncula , Echiura , Chaetognatha , and Phoronida ; Mollusca including shellfish , squid , octopus ; Arthropoda including Chelicerata and Crustacea ; Porifera ; Bryozoa ; Echinodermata including starfish ; and Urochordata including sea squirts or tunicates .
Over 10,000 [ 28 ] species of fungi are known from marine environments. [ 29 ] These are parasitic on marine algae or animals, or are saprobes on algae, corals, protozoan cysts, sea grasses, wood and other substrata, and can also be found in sea foam . [ 30 ] Spores of many species have special appendages which facilitate attachment to the substratum. [ 31 ] A very diverse range of unusual secondary metabolites is produced by marine fungi. [ 32 ]
A reported 33,400 species of fish , including bony and cartilaginous fish , had been described by 2016, [ 33 ] more than all other vertebrates combined. About 60% of fish species live in saltwater. [ 34 ]
Reptiles which inhabit or frequent the sea include sea turtles , sea snakes , terrapins , the marine iguana , and the saltwater crocodile . Most extant marine reptiles, except for some sea snakes, are oviparous and need to return to land to lay their eggs. Thus most species, excluding sea turtles, spend most of their lives on or near land rather than in the ocean. Despite their marine adaptations, most sea snakes prefer shallow waters nearby land, around islands, especially waters that are somewhat sheltered, as well as near estuaries. [ 35 ] [ 36 ] Some extinct marine reptiles, such as ichthyosaurs , evolved to be viviparous and had no requirement to return to land.
Birds adapted to living in the marine environment are often called seabirds . Examples include albatross , penguins , gannets , and auks . Although they spend most of their lives in the ocean, species such as gulls can often be found thousands of miles inland.
There are five main types of marine mammals: cetaceans ( toothed whales and baleen whales ); sirenians such as manatees ; pinnipeds including seals and the walrus ; sea otters ; and the polar bear . All are air-breathing, meaning that while some such as the sperm whale can dive for prolonged periods, all must return to the surface to breathe. [ 37 ] [ 38 ]
The marine ecosystem is large, and thus there are many sub-fields of marine biology. Most involve studying specializations of particular animal groups, such as phycology , invertebrate zoology and ichthyology . Other subfields study the physical effects of continual immersion in sea water and the ocean in general, adaptation to a salty environment, and the effects of changing various oceanic properties on marine life. A subfield of marine biology studies the relationships between oceans and ocean life, and global warming and environmental issues (such as carbon dioxide displacement). Recent marine biotechnology has focused largely on marine biomolecules , especially proteins , that may have uses in medicine or engineering. Marine environments are the home to many exotic biological materials that may inspire biomimetic materials .
Through constant monitoring of the ocean, there have been discoveries of marine life which could be used to create remedies for certain diseases such as cancer and leukemia. In addition, Ziconotide, an approved drug used to treat pain, was created from a snail which resides in the ocean. [ 39 ]
Marine biology is a branch of biology . It is closely linked to oceanography , especially biological oceanography , and may be regarded as a sub-field of marine science . It also encompasses many ideas from ecology . Fisheries science and marine conservation can be considered partial offshoots of marine biology (as well as environmental studies ). Marine chemistry , physical oceanography and atmospheric sciences are also closely related to this field.
An active research topic in marine biology is to discover and map the life cycles of various species and where they spend their time. Technologies that aid in this discovery include pop-up satellite archival tags , acoustic tags , and a variety of other data loggers . Marine biologists study how the ocean currents , tides and many other oceanic factors affect ocean life forms, including their growth, distribution and well-being. This has only recently become technically feasible with advances in GPS and newer underwater visual devices. [ 40 ]
Most ocean life breeds in specific places, nests in others, spends time as juveniles in still others, and in maturity in yet others. Scientists know little about where many species spend different parts of their life cycles especially in the infant and juvenile years. For example, it is still largely unknown where juvenile sea turtles and some sharks in the first year of their life travel. Recent advances in underwater tracking devices are illuminating what we know about marine organisms that live at great ocean depths. [ 41 ] The information that pop-up satellite archival tags gives aids in fishing closures for certain times of the year and the development of marine protected areas . This data is important to both scientists and fishermen because they are discovering that, by restricting commercial fishing in one small area, they can have a large impact in maintaining a healthy fish population in a much larger area.
The study of marine biology dates to Aristotle (384–322 BC), who made many observations of life in the sea around Lesbos , laying the foundation for many future discoveries. [ 43 ] In 1768, Samuel Gottlieb Gmelin (1744–1774) published the Historia Fucorum , the first work dedicated to marine algae and the first book on marine biology to use the new binomial nomenclature of Linnaeus . It included elaborate illustrations of seaweed and marine algae on folded leaves. [ 44 ] [ 45 ] The British naturalist Edward Forbes (1815–1854) is generally regarded as the founder of the science of marine biology. [ 46 ] The pace of oceanographic and marine biology studies quickly accelerated during the course of the 19th century.
The observations made in the first studies of marine biology fueled the Age of Discovery and exploration that followed. During this time, a vast amount of knowledge was gained about the life that exists in the oceans of the world. Many voyages contributed significantly to this pool of knowledge. Among the most significant were the voyages of HMS Beagle where Charles Darwin came up with his theories of evolution and on the formation of coral reefs . [ 47 ] Another important expedition was undertaken by HMS Challenger , where findings were made of unexpectedly high species diversity among fauna stimulating much theorizing by population ecologists on how such varieties of life could be maintained in what was thought to be such a hostile environment. [ 48 ] This era was important for the history of marine biology but naturalists were still limited in their studies because they lacked technology that would allow them to adequately examine species that lived in deep parts of the oceans.
The creation of marine laboratories was important because it allowed marine biologists to conduct research and process their specimens from expeditions. The oldest marine laboratory in the world, Station biologique de Roscoff , was established in Concarneau, France founded by the College of France in 1859. [ 49 ] In the United States, the Scripps Institution of Oceanography dates back to 1903, while the prominent Woods Hole Oceanographic Institute was founded in 1930. [ 50 ] The development of technology such as sound navigation and ranging , scuba diving gear, submersibles and remotely operated vehicles allowed marine biologists to discover and explore life in deep oceans that was once thought to not exist. [ 51 ] Public interest in the subject continued to develop in the post-war years with the publication of Rachel Carson 's sea trilogy (1941–1955).
In 1960, the bathyscaphe Trieste descended the furthest point man had yet traveled, bottoming Challenger's Deep at 35,797 feet. [ 21 ] The vessel was captained by Jacques Piccard and Don Walsh , whose discoveries while at the bottom of the ocean bolstered scientific discussion and interest about life in the hadal zone. [ 21 ] [ 22 ] [ 23 ] | https://en.wikipedia.org/wiki/Marine_biology |
The marine biology dredge is used to sample organisms living on a rocky bottom or burrowing within the smooth muddy floor of the ocean ( benthic ) species. The dredge is pulled by a boat and operates at any depth on a cable or line, generally with a hydraulic winch. The dredge digs into the ocean floor and bring the animals to the surface where they are caught in a net that either follows behind or is a part of the digging apparatus.
Early dredging samplers did not have a closing device, and many organisms were washed out. This led to a mistaken impression that the deep-sea bed lacked species diversity, as theorised by Forbes in his Azoic hypothesis . Later samplers devised by Howard L. Sanders and the Epibenthic sled designed by Robert Hessler showed that deep-sea bottoms are sometimes rich in soft-bottom benthic species.
The first marine biology dredge was designed by Otto Friedrich Müller and in 1830 the results of two dredging expeditions undertaken by Henri Milne-Edwards and his friend Jean Victoire Audouin during 1826 and 1828 in the neighbourhood of Granville were published. This was remarkable for clearly distinguishing the marine fauna of that portion of the French coast into four zones.
Müller's design was modified by the Dublin naturalist Robert Ball in 1838 and at the Birmingham meeting of the British Association for the Advancement of Science in 1839 a committee was appointed for dredging research with a view to the investigation of the marine zoology of Great Britain, the illustration of the geographical distribution of marine animals, and the more accurate determination of the fossils of the Pliocene period. The committee was led by Edward Forbes . Later annual reports of the British Association contained communications from the English, Scottish and Irish branches of the committee, and in 1850 Forbes submitted its first general report on British marine zoology. Ball's dredge was still in use in 1910.
In the 20th century the 'anchor-dredge' was developed to sample deep burrowing animals. It is not towed but digs in, and is released, in the manner of an anchor.
The wide variety of dredges and other benthic sampling equipment makes site comparison difficult. | https://en.wikipedia.org/wiki/Marine_biology_dredge |
Marine botany is the study of flowering vascular plant species and marine algae that live in shallow seawater of the open ocean and the littoral zone , along shorelines of the intertidal zone , coastal wetlands, and low-salinity brackish water of estuaries .
It is a branch of marine biology and botany .
There are five kingdoms that present-day classifications group organisms into: the Monera , Protist , Plantae , Fungi , and Animalia .
Less than 2,000 species of bacteria occur in the marine environment out of the 100,000 species. Although this group of species is small, they play a tremendous role in energy transfer, mineral cycles, and organic turnover. [ 1 ] The monera differs from the four other kingdoms as "members of the Monera have a prokaryotic cytology in which the cells lack membrane-bound organelles such as chloroplasts , mitochondria , nuclei, and complex flagella ." [ 1 ]
The bacteria can be divided into two major subkingdoms: Eubacteria and Archaebacteria.
Eubacteria include the only bacteria that contain chlorophyll a. Not only that, but Eubacteria are placed in the divisions of Cyanobacteria and Prochlorophyta. [ 1 ]
Characteristics of Eubacteria:
Archaebacteria are a type of single-cell organism and have a number of characteristics not seen in more "modern" cell types. [ 3 ] These characteristics include:
Types of Archaebacteria:
While both are prokaryotic, these organisms exist in different biological domains because of how genetically different they are. Some believe archaebacteria are some of the oldest forms of life on Earth while eubacteria arose later in evolutionary history. As eubacteria are found in almost all environments, archaebacteria have been pushed to only the most extreme environments. These extreme environments include: high salinity lakes, thermal hot springs, and deep within the Earth's crust. [ 2 ] Other differences include:
The Protist kingdom contains species that have been categorized due to the simplicity of their structure and being unicellular. These include protozoa , algae and slime molds . In marine ecosystems, macroalgae and microalgae make up a large portion of the photosynthetic organisms found. The algae can be then further categorized based on these characteristics:
The algae in the Protist kingdom can be placed into three different categories of macroalgae/seaweeds—phaeophyta, rhodophyta or chlorophyta. The microalgae in these marine environments can be categorized into four varieties—pyrrhophyta, chrysophyta, euglenophyta or cryptophyta. [ 1 ]
Examples of the types of organisms found in the Protist Kingdom are red, green and brown algae.
The Plantae Kingdoms consists of angiosperms-plants that produce seeds or flower as a part of their reproductive system. [ 4 ] About 0.085% of the 300,000 Angiosperms believed to exist can be found in marine like environments. [ 1 ]
Some examples of what plants in this kingdom exist are mosses , ferns , seagrasses , mangroves , and salt marsh plants—the last three being the three major communities of angiosperms in marine waters.
Seagrasses are recognized as some of the most important member to marine communities. It is the only true submerged angiosperm and can help determine the state of an ecosystem. [ 1 ] Seagrass helps identify the conditions of an ecosystem, as the presence of this plant aids the environment by: Stabilizing the water's bottom, providing shelter and food for animals, and maintaining water quality. [ 5 ]
Marine ecology and marine botany include: | https://en.wikipedia.org/wiki/Marine_botany |
Marine chemistry , also known as ocean chemistry or chemical oceanography , is the study of the chemical composition and processes of the world’s oceans, including the interactions between seawater, the atmosphere, the seafloor, and marine organisms. [ 2 ] This field encompasses a wide range of topics, such as the cycling of elements like carbon, nitrogen, and phosphorus, the behavior of trace metals, and the study of gases and nutrients in marine environments. Marine chemistry plays a crucial role in understanding global biogeochemical cycles , ocean circulation , and the effects of human activities, such as pollution and climate change, on oceanic systems. [ 2 ] It is influenced by plate tectonics and seafloor spreading , turbidity , currents , sediments , pH levels, atmospheric constituents, metamorphic activity, and ecology.
The impact of human activity on the chemistry of the Earth's oceans has increased over time, with pollution from industry and various land-use practices significantly affecting the oceans. Moreover, increasing levels of carbon dioxide in the Earth's atmosphere have led to ocean acidification , which has negative effects on marine ecosystems. The international community has agreed that restoring the chemistry of the oceans is a priority, and efforts toward this goal are tracked as part of Sustainable Development Goal 14 .
Due to the interrelatedness of the ocean, chemical oceanographers frequently work on problems relevant to physical oceanography , geology and geochemistry , biology and biochemistry , and atmospheric science . Many of them are investigating biogeochemical cycles , and the marine carbon cycle in particular attracts significant interest due to its role in carbon sequestration and ocean acidification . [ 3 ] Other major topics of interest include analytical chemistry of the oceans, marine pollution , and anthropogenic climate change .
DOM is a critical component of the ocean's carbon pool and includes many molecules such as amino acids, sugars, and lipids. It represents about 90% of the total organic carbon in marine environments. [ 4 ] Colored dissolved organic matter (CDOM) is estimated to range from 20-70% of the carbon content of the oceans, being higher near river outlets and lower in the open ocean. [ 5 ] DOM can be recycled and put back into the food web through a process called microbial loop which is essential for nutrient cycling and supporting primary productivity. [ 6 ] It also plays a vital role in the global regulation of oceanic carbon storage, as some forms resist microbial degradation and may exist within the ocean for centuries. [ 7 ] Marine life is similar mainly in biochemistry to terrestrial organisms, and is the most prolific source of halogenated organic compounds . [ 8 ]
POM includes of large organic particles, such as organisms, fecal pellets, and detritus, which settle through the water column. It is a major component of the biological pump, a process by which carbon is transferred from the surface ocean to the deep sea. As POM sinks, it decomposes by bacterial activity, releasing nutrients and carbon dioxide. The refractory POM fraction can settle on the ocean floor and make relevant contributions to carbon sequestration over a very long period of time [ 9 ]
The ocean is home to a variety of marine organisms known as extremophiles – organisms that thrive in extreme conditions of temperature, pressure, and light availability. Extremophiles inhabit many unique habitats in the ocean, such as hydrothermal vents , black smokers, cold seeps , hypersaline regions, and sea ice brine pockets . Some scientists have speculated that life may have evolved from hydrothermal vents in the ocean.
In hydrothermal vents and similar environments, many extremophiles acquire energy through chemoautotrophy , using chemical compounds as energy sources, rather than light as in photoautotrophy . Hydrothermal vents enrich the nearby environment in chemicals such as elemental sulfur , H 2 , H 2 S , Fe 2+ , and methane . Chemoautotrophic organisms, primarily prokaryotes, derive energy from these chemicals through redox reactions . These organisms then serve as food sources for higher trophic levels , forming the basis of unique ecosystems.
Several different metabolisms are present in hydrothermal vent ecosystems. Many marine microorganisms, including Thiomicrospira , Halothiobacillus , and Beggiatoa , are capable of oxidizing sulfur compounds, including elemental sulfur and the often toxic compound H 2 S. H 2 S is abundant in hydrothermal vents, formed through interactions between seawater and rock at the high temperatures found within vents. This compound is a major energy source, forming the basis of the sulfur cycle in hydrothermal vent ecosystems. In the colder waters surrounding vents, sulfur-oxidation can occur using oxygen as an electron acceptor ; closer to the vents, organisms must use alternate metabolic pathways or utilize another electron acceptor, such as nitrate. Some species of Thiomicrospira can utilize thiosulfate as an electron donor, producing elemental sulfur. Additionally, many marine microorganisms are capable of iron-oxidation, such as Mariprofundus ferrooxydans . Iron-oxidation can be oxic, occurring in oxygen-rich parts of the ocean, or anoxic, requiring either an electron acceptor such as nitrate or light energy. In iron-oxidation, Fe(II) is used as an electron donor ; conversely, iron-reducers utilize Fe(III) as an electron acceptor. These two metabolisms form the basis of the iron-redox cycle and may have contributed to banded iron formations .
At another extreme, some marine extremophiles inhabit sea ice brine pockets where temperature is very low and salinity is very high. Organisms trapped within freezing sea ice must adapt to a rapid change in salinity up to 3 times higher than that of regular seawater, as well as the rapid change to regular seawater salinity when ice melts. Most brine-pocket dwelling organisms are photosynthetic, therefore, these microenvironments can become hyperoxic, which can be toxic to its inhabitants. Thus, these extremophiles often produce high levels of antioxidants. [ 10 ]
Seafloor spreading on mid-ocean ridges is a global scale ion-exchange system. [ 11 ] Hydrothermal vents at spreading centers introduce various amounts of iron , sulfur , manganese , silicon and other elements into the ocean, some of which are recycled into the ocean crust . Helium-3 , an isotope that accompanies volcanism from the mantle, is emitted by hydrothermal vents and can be detected in plumes within the ocean. [ 12 ]
Spreading rates on mid-ocean ridges vary between 10 and 200 mm/yr. Rapid spreading rates cause increased basalt reactions with seawater. The magnesium / calcium ratio will be lower because more magnesium ions are being removed from seawater and consumed by the rock, and more calcium ions are being removed from the rock and released to seawater. Hydrothermal activity at ridge crest is efficient in removing magnesium. [ 13 ] A lower Mg/Ca ratio favors the precipitation of low-Mg calcite polymorphs of calcium carbonate ( calcite seas ). [ 11 ]
Slow spreading at mid-ocean ridges has the opposite effect and will result in a higher Mg/Ca ratio favoring the precipitation of aragonite and high-Mg calcite polymorphs of calcium carbonate ( aragonite seas ). [ 11 ]
Experiments show that most modern high-Mg calcite organisms would have been low-Mg calcite in past calcite seas, [ 14 ] meaning that the Mg/Ca ratio in an organism's skeleton varies with the Mg/Ca ratio of the seawater in which it was grown.
The mineralogy of reef-building and sediment-producing organisms is thus regulated by chemical reactions occurring along the mid-ocean ridge, the rate of which is controlled by the rate of sea-floor spreading. [ 13 ] [ 14 ]
Marine pollution occurs when substances used or spread by humans, such as industrial , agricultural , and residential waste ; particles ; noise ; excess carbon dioxide ; or invasive organisms enter the ocean and cause harmful effects there. The majority of this waste (80%) comes from land-based activity, although marine transportation significantly contributes as well. [ 15 ] It is a combination of chemicals and trash, most of which comes from land sources and is washed or blown into the ocean. This pollution results in damage to the environment , to the health of all organisms, and to economic structures worldwide. [ 16 ] Since most inputs come from land, via rivers , sewage , or the atmosphere , it means that continental shelves are more vulnerable to pollution. Air pollution is also a contributing factor, as it carries iron, carbonic acid, nitrogen , silicon, sulfur, pesticides , and dust particles into the ocean. [ 17 ] The pollution often comes from nonpoint sources such as agricultural runoff , wind-blown debris , and dust. These nonpoint sources are largely due to runoff that enters the ocean through rivers, but wind-blown debris and dust can also play a role, as these pollutants can settle into waterways and oceans. [ 18 ] Pathways of pollution include direct discharge, land runoff, ship pollution , bilge pollution , dredging (which can create dredge plumes ), atmospheric pollution and, potentially, deep sea mining .
Increased carbon dioxide levels, mostly from burning fossil fuels , are changing ocean chemistry. Global warming and changes in salinity [ 19 ] have significant implications for the ecology of marine environments . [ 20 ]
Ocean acidification is the ongoing decrease in the pH of the Earth's ocean . Between 1950 and 2020, the average pH of the ocean surface fell from approximately 8.15 to 8.05. [ 21 ] Carbon dioxide emissions from human activities are the primary cause of ocean acidification, with atmospheric carbon dioxide (CO 2 ) levels exceeding 422 ppm (as of 2024 [update] ). [ 22 ] CO 2 from the atmosphere is absorbed by the oceans. This chemical reaction produces carbonic acid ( H 2 CO 3 ) which dissociates into a bicarbonate ion ( HCO − 3 ) and a hydrogen ion ( H + ). The presence of free hydrogen ions ( H + ) lowers the pH of the ocean, increasing acidity (this does not mean that seawater is acidic yet; it is still alkaline , with a pH higher than 8). Marine calcifying organisms , such as mollusks and corals , are especially vulnerable because they rely on calcium carbonate to build shells and skeletons. [ 23 ]
Ocean deoxygenation is the reduction of the oxygen content in different parts of the ocean due to human activities. [ 28 ] [ 29 ] There are two areas where this occurs. Firstly, it occurs in coastal zones where eutrophication has driven some quite rapid (in a few decades) declines in oxygen to very low levels. [ 28 ] This type of ocean deoxygenation is also called dead zones . Secondly, ocean deoxygenation occurs also in the open ocean. In that part of the ocean, there is nowadays an ongoing reduction in oxygen levels. As a result, the naturally occurring low oxygen areas (so called oxygen minimum zones (OMZs)) are now expanding slowly. [ 30 ] This expansion is happening as a consequence of human caused climate change . [ 31 ] [ 32 ] The resulting decrease in oxygen content of the oceans poses a threat to marine life , as well as to people who depend on marine life for nutrition or livelihood. [ 33 ] [ 34 ] [ 35 ] A decrease in ocean oxygen levels affects how productive the ocean is, how nutrients and carbon move around , and how marine habitats function. [ 36 ] [ 37 ]
As the oceans become warmer this increases the loss of oxygen in the oceans. This is because the warmer temperatures increase ocean stratification . The reason for this lies in the multiple connections between density and solubility effects that result from warming. [ 38 ] [ 39 ] As a side effect, the availability of nutrients for marine life is reduced, therefore adding further stress to marine organisms .
The rising temperatures in the oceans also cause a reduced solubility of oxygen in the water, which can explain about 50% of oxygen loss in the upper level of the ocean (>1000 m). Warmer ocean water holds less oxygen and is more buoyant than cooler water. This leads to reduced mixing of oxygenated water near the surface with deeper water, which naturally contains less oxygen. Warmer water also raises oxygen demand from living organisms; as a result, less oxygen is available for marine life. [ 40 ]
Early inquiries about marine chemistry usually concerned the origin of salinity in the ocean, including work by Robert Boyle . Modern chemical oceanography began as a field with the 1872–1876 Challenger expedition , led by the British Royal Navy which made the first systematic measurements of ocean chemistry. The chemical analysis of these samples providing the first systematic study of the composition of seawater was conducted by John Murray and George Forchhammer, leading to a better understanding of elements like chloride, sodium, and sulfate in ocean waters [ 44 ]
The early 20th century saw significant advancements in marine chemistry, particularly with more accurate analytical techniques. Scientists like Martin Knudsen created the Knudsen Bottle, an instrument used to collect water samples from different ocean depths. [ 45 ] Over the past three decades (1970s, 19802, and 1990s), a comprehensive evaluation of advancements in chemical oceanography was compiled through a National Science Foundation initiative known as Futures of Ocean Chemistry in the United States (FOCUS). This project brought together numerous prominent chemical oceanographers, marine chemists, and geochemists to contribute to the FOCUS report.
After World War II, advancements in geochemical techniques propelled marine chemistry into a new era. Researchers began using isotopic analysis to study ocean circulation and the carbon cycle. Roger Revelle and Hans Suess pioneered using radiocarbon dating to investigate oceanic carbon reservoirs and their exchange with the atmosphere. [ 46 ]
Since the 1970s, the development of highly sophisticated instruments and computational models has revolutionized marine chemistry. Scientists can now measure trace metals , organic compounds , and isotopic ratios with unprecedented precision. Studies of marine biogeochemical cycles, including the carbon , nitrogen , and sulfur cycles , have become an area of interest to understand global climate change . The use of remote sensing technology and global ocean observation programs, such as the International Geosphere-Biosphere Programme (IGBP), has provided large-scale data on ocean chemistry, allowing scientists to monitor ocean acidification , deoxygenation , and other critical issues affecting the marine environment. [ 47 ]
Chemical oceanographers collect and measure chemicals in seawater, using the standard toolset of analytical chemistry as well as instruments like pH meters , electrical conductivity meters , fluorometers , and dissolved CO₂ meters. Most data are collected through shipboard measurements and from autonomous floats or buoys , but remote sensing is used as well. On an oceanographic research vessel , a CTD is used to measure electrical conductivity , temperature , and pressure , [ 48 ] and is often mounted on a rosette of Nansen bottles to collect seawater for analysis. [ 49 ] Sediments are commonly studied with a box corer or a sediment trap , and older sediments may be recovered by scientific drilling .
Advanced analytical equipment such as mass spectrometers and chromatographs are applied to detect trace elements, isotopes, and organic compounds. This allows for precisely measuring nutrients, gases, and pollutants in marine environments. [ 50 ] In recent years, autonomous underwater vehicles (AUVs) and remote sensing technology have enabled continuous, large-scale ocean chemistry monitoring, particularly for tracking changes in ocean acidification and nutrient cycles. [ 51 ]
The chemistry of the subsurface ocean of Europa may be Earthlike. [ 52 ] The subsurface ocean of Enceladus vents hydrogen and carbon dioxide to space. [ 53 ] | https://en.wikipedia.org/wiki/Marine_chemistry |
Marine cloud brightening (MCB), also known as marine cloud seeding or marine cloud engineering , may be a way to make stratocumulus clouds over the sea brighter, thus reflecting more sunlight back into space in order to limit global warming . It is one of two such methods that might feasibly have a substantial climate impact, but is lower in the atmosphere than stratospheric aerosol injection . [ 1 ] It may be able to keep local areas from overheating. If used on a large scale it might reduce the Earth's albedo ; and so, in combination with greenhouse gas emissions reduction , limit climate change and its risks to people and the environment . If implemented, the cooling effect would be expected to be felt rapidly and to be reversible on fairly short time scales. However, technical barriers remain to large-scale marine cloud brightening, and it could not offset all the current warming. [ 2 ] [ 3 ] As clouds are complicated and poorly understood, the risks of marine cloud brightening are unclear as of 2025.
Very small droplets of sea water are sprayed into the air to increase cloud reflectivity. The fine particles of sea salt enhance cloud condensation nuclei , making more cloud droplets so making the clouds more reflective. [ 4 ] [ 5 ] : 628 MCB could be implemented using fleets of unmanned rotor ships to disperse seawater mist into the air. [ 6 ] : 43 Small-scale field tests were conducted on the Great Barrier Reef in 2024. [ 7 ]
Marine cloud brightening is based on phenomena that are currently observed in the climate system. Today, emissions particles, such as soot , mix with clouds in the atmosphere and increase the amount of sunlight they reflect, reducing warming. This cooling effect is estimated at between 0.5 and 1.5 °C (0.9 and 2.7 °F), and is one of the most important unknowns in climate. [ 8 ] Marine cloud brightening proposes to generate a similar effect using benign material, such as sea salt. Marine stratocumulus clouds are thought to be the most suitable because of their prevalence, coverage, accessibility, and generally low cloud drop number concentration. [ 9 ] MCB also makes the clouds last longer. [ 10 ] Although stratospheric aerosol injection would be much higher up, it could diffuse sunlight and so also brighten low-level marine clouds. [ 11 ]
Most clouds are quite reflective , redirecting incoming solar radiation back into space. Increasing clouds' albedo would increase the portion of incoming solar radiation that is reflected, in turn cooling the planet. Clouds consist of water droplets, and clouds with smaller droplets are more reflective (because of the Twomey effect ). Cloud condensation nuclei are necessary for water droplet formation. The central idea underlying marine cloud brightening is to add aerosols to atmospheric locations where clouds form. These would then act as cloud condensation nuclei, increasing the cloud albedo .
Marine cloud brightening on a small scale already occurs unintentionally due to the aerosols in ships' exhaust , leaving ship tracks . [ 12 ] Changes to shipping regulations enacted by the United Nations’ International Maritime Organization to reduce certain aerosols are hypothesized to be leading to reduced cloud cover and increased oceanic warming, providing additional support to the potential effectiveness of marine cloud brightening at modifying ocean temperature. [ 13 ] Different cloud regimes are likely to have differing susceptibility to brightening strategies, with marine stratocumulus clouds (low, layered clouds over ocean regions) most sensitive to aerosol changes. [ 14 ] [ 15 ] These marine stratocumulus clouds are thus typically proposed as the target. They are common over the cooler regions of subtropical and midlatitude oceans, where their coverage can average over 50% over a year. [ 16 ] The leading possible source of additional cloud condensation nuclei is salt from seawater , although there are others. [ 17 ]
Even though the importance of aerosols for the formation of clouds is, in general, well understood, many uncertainties remain. The IPCC Fifth Assessment Report considers aerosol-cloud interactions as one of the current major challenges in climate modeling in general. [ 18 ] In particular, the number of droplets does not increase proportionally when more aerosols are present, and can even decrease. [ 19 ] [ 20 ] Extrapolating the effects of particles on clouds observed on the microphysical scale to the regional, climatically relevant, scale is not straightforward. [ 21 ] For example deployment in the South Pacific or South Atlantic could increase rainfall in western and central Africa but reduce it in southern Africa. [ 22 ]
It has been suggested that MCB should be used to preserve Arctic sea ice. [ 23 ]
The modeling evidence of the global climatic effects of marine cloud brightening remains limited. [ 1 ] Current modeling research indicates that marine cloud brightening could substantially cool the planet. A 2020 study found a substantial increase in cloud reflectivity from shipping in the southeast Atlantic basin, suggesting that a regional-scale test of MCB in stratocumulus‐dominated regions could be successful. [ 24 ]
Studies in the late 2010s estimated that this technique could produce up to 2 W/m 2 of negative radiative forcing , [ a ] [ 2 ] [ 3 ] which is less than human-caused radiative forcing of almost 3 W/m 2 .
The climatic impacts of marine cloud brightening would be rapidly responsive and reversible. If the brightening activity were to change in intensity, or stop altogether, then the clouds' brightness would respond within a few days to weeks, as the cloud condensation nuclei particles precipitate naturally. [ 1 ]
Again unlike stratospheric aerosol injection, marine cloud brightening might be able to be used regionally, albeit in a limited manner. [ 25 ] Marine stratocumulus clouds are common in particular regions, specifically the eastern Pacific Ocean and the eastern South Atlantic Ocean. A typical finding among simulation studies was a persistent cooling of the Pacific, similar to the La Niña phenomenon, and, despite the localized nature of the albedo change, an increase in polar sea ice. [ 26 ] [ 27 ] [ 28 ] [ 29 ] [ 30 ] Studies aim at making simulation findings derived from different models comparable. [ needs update ] [ 31 ] [ 32 ]
There is some potential for changes to precipitation patterns and amplitude, [ 28 ] [ 33 ] [ 34 ] although modeling suggests that the changes are likely less than those for stratospheric aerosol injection and considerably smaller than for unabated anthropogenic global warming. [ 1 ] The effects may be like La Niña . [ 35 ]
Regional implementations of MCB would need care to avoid causing possibly adverse consequences in areas far away from the region they are aiming to help. For example, a potential Marine Cloud Brightening aimed at cooling the Western United States could risk causing increasing heat in Europe, due to climate teleconnections such as unintended perturbation of the Atlantic meridional overturning circulation . [ 36 ]
Marine cloud brightening was originally suggested by John Latham in 1990. [ 37 ] Because clouds remain a major source of uncertainty in climate change, some research projects into cloud reflectivity in the general climate change context have provided insight into marine cloud brightening specifically. For example, one project released smoke behind ships in the Pacific Ocean and monitored the particulates' impact on clouds. [ 38 ] Although this was done in order to better understand clouds and climate change, the research has implications for marine cloud brightening.
A research coalition called the Marine Cloud Brightening Project was formed in order to coordinate research activities. Its proposed program includes modeling, field experiments, technology development and policy research to study cloud-aerosol effects and marine cloud brightening. The proposed program currently serves as a model for process-level (environmentally benign) experimental programs in the atmosphere. [ 39 ] [ better source needed ] Formed in 2009 by Kelly Wanser with support from Ken Caldeira , [ 40 ] the project is now housed at the University of Washington . [ 41 ]
The shipping industry may have been carrying out an unintentional experiment in marine cloud brightening due to the emissions of ships and causing a global temperature reduction of as much as 0.25 ˚C lower than they would otherwise have been. [ 42 ] A 2020 study found a substantial increase in cloud reflectivity from shipping in the southeast Atlantic, suggesting that a regional-scale test of MCB in stratocumulus‐dominated regions could be successful. [ 24 ]
Marine cloud brightening is being field tested as a way to shade and cool the Great Barrier Reef in Australia, as part of the Reef Restoration and Adaptation Program. [ 43 ] As of 2024 it is thought that the salt spray can deliver particles into low clouds. [ 44 ] Although research is not yet complete, experts on the project say that if deployed it would not effect any other countries. [ 45 ] Unlike experiments in some other places, this research is supported locally and by most Australians. [ 46 ]
The leading proposed method for marine cloud brightening is to generate a fine mist of salt from seawater, and to deliver into targeted banks of marine stratocumulus clouds from ships traversing the ocean. This requires technology that can generate optimally-sized (~200 nm) sea-salt particles and deliver them at sufficient force and scale to penetrate low-lying marine clouds. The resulting spray mist must then be delivered continuously into target clouds over the ocean. [ 6 ] : 39–43
In the earliest published studies, John Latham and Stephen Salter proposed a fleet of around 1500 unmanned Rotor ships , or Flettner ships, that would spray mist created from seawater into the air. [ 14 ] [ 47 ]
Subsequent researchers determined that transport efficiency was only relevant for use at scale, and that for research requirements, standard ships could be used for transport. (Some researchers considered aircraft as an option, but concluded that it would be too costly.) Droplet generation and delivery technology is critical to progress, and technology research has been focused on solving this challenging problem. [ citation needed ]
As of 2025 how far the plume would travel and how much would reach the cloud layer is not known. [ 48 ]
Other methods were proposed and discounted, including:
The costs of marine cloud brightening remain largely unknown. A report of the US National Academies suggested roughly five billion US dollars annually for a large deployment program. [ 1 ]
Marine cloud brightening would be governed primarily by international law because it would likely take place outside of countries' territorial waters , and because it would affect the environment of other countries and of the oceans. For the most part, the international law governing solar radiation management in general would apply. For example, according to customary international law , if a country were to conduct or approve a marine cloud brightening activity that would pose significant risk of harm to the environments of other countries or of the oceans, then that country would be obligated to minimize this risk pursuant to a due diligence standard. In this, the country would need to require authorization for the activity (if it were to be conducted by a private actor), perform a prior environmental impact assessment , notify and cooperate with potentially affected countries, and inform the public. [ 51 ]
Marine cloud brightening activities would be further governed by the international law of the sea, and particularly by the United Nations Convention on the Law of the Sea (UNCLOS). Parties to the UNCLOS are obligated to "protect and preserve the marine environment," including by preventing, reducing, and controlling pollution of the marine environment from any source. [ 52 ] [ 53 ] The "marine environment" is not defined but is widely interpreted as including the ocean's water, lifeforms, and the air above. [ 54 ] "Pollution of the marine environment" is defined in a way that includes global warming and greenhouse gases. [ 55 ] [ 56 ] The UNCLOS could thus be interpreted as obligating the involved parties to use methods such as marine cloud brightening if these were found to be effective and environmentally benign. Whether marine cloud brightening itself could be such pollution of the marine environment is unclear. At the same time, in combating pollution, Parties are "not to transfer, directly or indirectly, damage or hazards from one area to another or transform one type of pollution into another." [ 57 ] If marine cloud brightening were found to cause damage or hazards, the UNCLOS could prohibit it. If marine cloud brightening activities were to be "marine scientific research"—also an undefined term—then UNCLOS Parties have a right to conduct the research, subject to some qualifications. [ 58 ] [ 59 ] Like all other ships, those that would conduct marine cloud brightening must bear the flag of the country that has given them permission to do so and to which the ship has a genuine link, even if the ship is unmanned or automated. [ 60 ] The flagged state must exercise its jurisdiction over those ships. [ 61 ] The legal implications would depend on, among other things, whether the activity were to occur in territorial waters , an exclusive economic zone (EEZ), or the high seas ; and whether the activity was scientific research or not. Coastal states would need to approve any marine cloud brightening activities in their territorial waters. In the EEZ, the ship must comply with the coastal state's laws and regulations. [ 62 ] It appears that the state conducting marine cloud brightening activities in another state's EEZ would not need the latter's permission, unless the activity were marine scientific research. In that case, the coastal state should grant permission in normal circumstances. [ 63 ] States would be generally free to conduct marine cloud brightening activities on the high seas, provided that this is done with "due regard" for other states' interests. There is some legal unclarity regarding unmanned or automated ships. [ 64 ]
As of 2025 MCB is being considered for addition to the London Convention on the Prevention of Marine Pollution by Dumping of Wastes and Other Matter , which might mean that parties to the convention would have to assess projects under Annex V of the convention’s London Protocol. [ 65 ]
Marine cloud brightening appears to have most of the advantages and disadvantages of solar radiation management in general. For example, it presently appears to be inexpensive relative to suffering climate change damages and greenhouse gas emissions abatement, fast acting, and reversible in its direct climatic effects. Some advantages and disadvantages are specific to it, relative to other proposed solar radiation management techniques.
Compared with other proposed solar radiation management methods, such as stratospheric aerosols injection , marine cloud brightening may be able to be partially localized in its effects. [ 25 ] This could, for example, be used to stabilize the West Antarctic Ice Sheet . Furthermore, marine cloud brightening, as it is currently envisioned, would use only natural substances sea water and wind, instead of introducing human-made substances into the environment.
Potential disadvantages include that specific MCB implementations could have a varying effect across time; the same intervention might even become a net contributor to global warming some years after being first launched, though this could be avoided with careful planning. [ 36 ] | https://en.wikipedia.org/wiki/Marine_cloud_brightening |
A marine coastal ecosystem is a marine ecosystem which occurs where the land meets the ocean. Worldwide there is about 620,000 kilometres (390,000 mi) of coastline. Coastal habitats extend to the margins of the continental shelves , occupying about 7 percent of the ocean surface area. Marine coastal ecosystems include many very different types of marine habitats , each with their own characteristics and species composition. They are characterized by high levels of biodiversity and productivity.
For example, estuaries are areas where freshwater rivers meet the saltwater of the ocean, creating an environment that is home to a wide variety of species, including fish, shellfish, and birds. Salt marshes are coastal wetlands which thrive on low-energy shorelines in temperate and high-latitude areas, populated with salt-tolerant plants such as cordgrass and marsh elder that provide important nursery areas for many species of fish and shellfish. Mangrove forests survive in the intertidal zones of tropical or subtropical coasts, populated by salt-tolerant trees that protect habitat for many marine species, including crabs, shrimp, and fish.
Further examples are coral reefs and seagrass meadows , which are both found in warm, shallow coastal waters. Coral reefs thrive in nutrient-poor waters on high-energy shorelines that are agitated by waves. They are underwater ecosystem made up of colonies of tiny animals called coral polyps . These polyps secrete hard calcium carbonate skeletons that builds up over time, creating complex and diverse underwater structures. These structures function as some of the most biodiverse ecosystems on the planet, providing habitat and food for a huge range of marine organisms. Seagrass meadows can be adjacent to coral reefs. These meadows are underwater grasslands populated by marine flowering plants that provide nursery habitats and food sources for many fish species, crabs and sea turtles , as well as dugongs . In slightly deeper waters are kelp forests , underwater ecosystems found in cold, nutrient-rich waters, primarily in temperate regions. These are dominated by a large brown algae called kelp , a type of seaweed that grows several meters tall, creating dense and complex underwater forests. Kelp forests provide important habitats for many fish species, sea otters and sea urchins .
Directly and indirectly, marine coastal ecosystems provide vast arrays of ecosystem services for humans, such as cycling nutrients and elements , and purifying water by filtering pollutants. They sequester carbon as a cushion against climate change . They protect coasts by reducing the impacts of storms, reducing coastal erosion and moderating extreme events. They provide essential nurseries and fishing grounds for commercial fisheries . They provide recreational services and support tourism. These ecosystems are vulnerable to various anthropogenic and natural disturbances, such as pollution , overfishing , and coastal development, which have significant impacts on their ecological functioning and the services they provide. Climate change is impacting coastal ecosystems with sea level rises , ocean acidification , and increased storm frequency and intensity. When marine coastal ecosystems are damaged or destroyed, there can be serious consequences for the marine species that depend on them, as well as for the overall health of the ocean ecosystem. Some conservation efforts are underway to protect and restore marine coastal ecosystems, such as establishing marine protected areas and developing sustainable fishing practices.
The Earth has approximately 620,000 kilometres (390,000 mi) of coastline. Coastal habitats extend to the margins of the continental shelves , occupying about 7 percent by area of the Earth's oceans. [ 1 ] These coastal seas are highly productive systems, providing an array of ecosystem services to humankind, such as processing of nutrient effluents from land and climate regulation. [ 2 ] However, coastal ecosystems are threatened by human-induced pressures such as climate change and eutrophication . In the coastal zone, the fluxes and transformations of nutrients and carbon sustaining coastal ecosystem functions and services are strongly regulated by benthic (that is, occurring at the seafloor ) biological and chemical processes. [ 2 ]
Coastal systems also contribute to the regulation of climate and nutrient cycles , by efficiently processing anthropogenic emissions from land before they reach the ocean. [ 3 ] [ 4 ] [ 5 ] [ 6 ] The high value of these ecosystem services is obvious considering that a large proportion of the world population lives close to the coast. [ 7 ] [ 8 ] [ 2 ]
Currently, coastal seas around the world are undergoing major ecological changes driven by human-induced pressures, such as climate change, anthropogenic nutrient inputs, overfishing and the spread of invasive species . [ 9 ] [ 10 ] In many cases, the changes alter underlying ecological functions to such an extent that new states are achieved and baselines are shifted . [ 11 ] [ 12 ] [ 2 ]
In 2015, the United Nations established 17 Sustainable Development Goals with the aim of achieving certain targets by 2030. Their mission statement for their 14th goal, Life below water , is to "conserve and sustainably use the oceans, seas and marine resources for sustainable development". [ 13 ] The United Nations has also declared 2021–2030 the UN Decade on Ecosystem Restoration , but restoration of coastal ecosystems is not receiving appropriate attention. [ 14 ]
Intertidal zones are the areas that are visible and exposed to air during low tide and covered up by saltwater during high tide. [ 15 ] There are four physical divisions of the intertidal zone with each one having its distinct characteristics and wildlife. These divisions are the Spray zone, High intertidal zone, Middle Intertidal zone, and Low intertidal zone. The Spray zone is a damp area that is usually only reached by the ocean and submerged only under high tides or storms. The high intertidal zone is submerged at high tide but remains dry for long periods between high tides. [ 15 ] Due to the large variance of conditions possible in this region, it is inhabited by resilient wildlife that can withstand these changes such as barnacles, marine snails, mussels and hermit crabs. [ 15 ] Tides flow over the middle intertidal zone two times a day and this zone has a larger variety of wildlife. [ 15 ] The low intertidal zone is submerged nearly all the time except during the lowest tides and life is more abundant here due to the protection that the water gives. [ 15 ]
Estuaries occur where there is a noticeable change in salinity between saltwater and freshwater sources. This is typically found where rivers meet the ocean or sea. The wildlife found within estuaries is unique as the water in these areas is brackish - a mix of freshwater flowing to the ocean and salty seawater. [ 16 ] Other types of estuaries also exist and have similar characteristics as traditional brackish estuaries. The Great Lakes are a prime example. There, river water mixes with lake water and creates freshwater estuaries. [ 16 ] Estuaries are extremely productive ecosystems that many humans and animal species rely on for various activities. [ 17 ] This can be seen as, of the 32 largest cities in the world, 22 are located on estuaries as they provide many environmental and economic benefits such as crucial habitat for many species, and being economic hubs for many coastal communities. [ 17 ] Estuaries also provide essential ecosystem services such as water filtration, habitat protection, erosion control, gas regulation nutrient cycling, and it even gives education, recreation and tourism opportunities to people. [ 18 ]
Lagoons are areas that are separated from larger water by natural barriers such as coral reefs or sandbars. There are two types of lagoons, coastal and oceanic/atoll lagoons. [ 19 ] A coastal lagoon is, as the definition above, simply a body of water that is separated from the ocean by a barrier. An atoll lagoon is a circular coral reef or several coral islands that surround a lagoon. Atoll lagoons are often much deeper than coastal lagoons. [ 20 ] Most lagoons are very shallow meaning that they are greatly affected by changed in precipitation, evaporation and wind. This means that salinity and temperature are widely varied in lagoons and that they can have water that ranges from fresh to hypersaline. [ 20 ] Lagoons can be found in on coasts all over the world, on every continent except Antarctica and is an extremely diverse habitat being home to a wide array of species including birds, fish, crabs, plankton and more. [ 20 ] Lagoons are also important to the economy as they provide a wide array of ecosystem services in addition to being the home of so many different species. Some of these services include fisheries, nutrient cycling, flood protection, water filtration, and even human tradition. [ 20 ]
Coral reefs are one of the most well-known marine ecosystems in the world, with the largest being the Great Barrier Reef . These reefs are composed of large coral colonies of a variety of species living together. The corals from multiple symbiotic relationships with the organisms around them. [ 21 ] Coral reefs are being heavily affected by global warming. They are one of the most vulnerable marine ecosystems. Due to marine heatwaves that have high warming levels coral reefs are at risk of a great decline, loss of its important structures, and exposure to higher frequency of marine heatwaves. [ 22 ]
Bivalve reefs provide coastal protection through erosion control and shoreline stabilization, and modify the physical landscape by ecosystem engineering , thereby providing habitat for species by facilitative interactions with other habitats such as tidal flat benthic communities, seagrasses and marshes . [ 24 ]
Vegetated coastal ecosystems occur throughout the world, as illustrated in the diagram on the right. Seagrass beds are found from cold polar waters to the tropics. Mangrove forests are confined to tropical and sub-tropical areas, while tidal marshes are found in all regions, but most commonly in temperate areas. Combined, these ecosystems cover about 50 million hectares and provide a diverse array of ecosystem services such as fishery production, coastline protection, pollution buffering, as well as high rates of carbon sequestration . [ 26 ] [ 25 ]
Rapid loss of vegetated coastal ecosystems through land-use change has occurred for centuries, and has accelerated in recent decades. Causes of habitat conversion vary globally and include conversion to aquaculture, agriculture, forest over-exploitation, industrial use, upstream dams, dredging, eutrophication of overlying waters, urban development, and conversion to open water due to accelerated sea-level rise and subsidence. [ 26 ] [ 25 ]
Vegetated coastal ecosystems typically reside over organic-rich sediments that may be several meters deep and effectively lock up carbon due to low-oxygen conditions and other factors that inhibit decomposition at depth. [ 27 ] These carbon stocks can exceed those of terrestrial ecosystems, including forests, by several times. [ 28 ] [ 29 ] When coastal habitats are degraded or converted to other land uses, the sediment carbon is destabilised or exposed to oxygen, and subsequent increased microbial activity releases large amounts of greenhouse gasses to the atmosphere or water column . [ 30 ] [ 27 ] [ 31 ] [ 32 ] [ 33 ] [ 34 ] The potential economic impacts that come from releasing stored coastal blue carbon to the atmosphere are felt worldwide. Economic impacts of greenhouse gas emissions in general stem from associated increases in droughts, sea level, and frequency of extreme weather events. [ 35 ] [ 25 ]
Coastal wetlands are among the most productive ecosystems on Earth and generate vital services that benefit human societies around the world. Sediment-stabilization by wetlands such as salt marshes and mangroves serves to protect coastal communities from storm-waves, flooding, and land erosion. [ 40 ] Coastal wetlands also reduce pollution from human waste, [ 41 ] [ 42 ] remove excess nutrients from the water column, [ 43 ] trap pollutants, [ 44 ] and sequester carbon. [ 45 ] Further, near-shore wetlands act as both essential nursery habitats and feeding grounds for game fish , supporting a diverse group of economically important species. [ 46 ] [ 47 ] [ 48 ] [ 49 ] [ 50 ]
Mangroves are trees or shrubs that grow in low-oxygen soil near coastlines in tropical or subtropical latitudes. [ 51 ] They are an extremely productive and complex ecosystem that connects the land and sea. Mangroves consist of species that are not necessarily related to each other and are often grouped for the characteristics they share rather than genetic similarity. [ 52 ] Because of their proximity to the coast, they have all developed adaptions such as salt excretion and root aeration to live in salty, oxygen-depleted water. [ 52 ] Mangroves can often be recognized by their dense tangle of roots that act to protect the coast by reducing erosion from storm surges, currents, wave, and tides. [ 51 ] The mangrove ecosystem is also an important source of food for many species as well as excellent at sequestering carbon dioxide from the atmosphere with global mangrove carbon storage is estimated at 34 million metric tons per year. [ 52 ]
Salt marshes are a transition from the ocean to the land, where fresh and saltwater mix. [ 53 ] The soil in these marshes is often made up of mud and a layer of organic material called peat. Peat is characterized as waterlogged and root-filled decomposing plant matter that often causes low oxygen levels (hypoxia). These hypoxic conditions causes growth of the bacteria that also gives salt marshes the sulfurous smell they are often known for. [ 54 ] Salt marshes exist around the world and are needed for healthy ecosystems and a healthy economy. They are extremely productive ecosystems and they provide essential services for more than 75 percent of fishery species and protect shorelines from erosion and flooding. [ 54 ] Salt marshes can be generally divided into the high marsh, low marsh, and the upland border. The low marsh is closer to the ocean, with it being flooded at nearly every tide except low tide. [ 53 ] The high marsh is located between the low marsh and the upland border and it usually only flooded when higher than usual tides are present. [ 53 ] The upland border is the freshwater edge of the marsh and is usually located at elevations slightly higher than the high marsh. This region is usually only flooded under extreme weather conditions and experiences much less waterlogged conditions and salt stress than other areas of the marsh. [ 53 ]
Seagrasses form dense underwater meadows which are among the most productive ecosystems in the world. They provide habitats and food for a diversity of marine life comparable to coral reefs. This includes invertebrates like shrimp and crabs, cod and flatfish, marine mammals and birds. They provide refuges for endangered species such as seahorses, turtles, and dugongs. They function as nursery habitats for shrimps, scallops and many commercial fish species. Seagrass meadows provide coastal storm protection by the way their leaves absorb energy from waves as they hit the coast. They keep coastal waters healthy by absorbing bacteria and nutrients, and slow the speed of climate change by sequestering carbon dioxide into the sediment of the ocean floor.
Seagrasses evolved from marine algae which colonized land and became land plants, and then returned to the ocean about 100 million years ago. However, today seagrass meadows are being damaged by human activities such as pollution from land runoff, fishing boats that drag dredges or trawls across the meadows uprooting the grass, and overfishing which unbalances the ecosystem. Seagrass meadows are currently being destroyed at a rate of about two football fields every hour.
Kelp forests occur worldwide throughout temperate and polar coastal oceans. [ 55 ] In 2007, kelp forests were also discovered in tropical waters near Ecuador . [ 56 ]
Physically formed by brown macroalgae , kelp forests provide a unique habitat for marine organisms [ 57 ] and are a source for understanding many ecological processes. Over the last century, they have been the focus of extensive research, particularly in trophic ecology, and continue to provoke important ideas that are relevant beyond this unique ecosystem. For example, kelp forests can influence coastal oceanographic patterns [ 58 ] and provide many ecosystem services . [ 59 ]
However, the influence of humans has often contributed to kelp forest degradation . Of particular concern are the effects of overfishing nearshore ecosystems, which can release herbivores from their normal population regulation and result in the overgrazing of kelp and other algae. [ 60 ] This can rapidly result in transitions to barren landscapes where relatively few species persist. [ 61 ] [ 62 ] Already due to the combined effects of overfishing and climate change , kelp forests have all but disappeared in many especially vulnerable places, such as Tasmania 's east coast and the coast of Northern California . [ 63 ] [ 64 ] The implementation of marine protected areas is one management strategy useful for addressing such issues, since it may limit the impacts of fishing and buffer the ecosystem from additive effects of other environmental stressors.
Coastal waters include the waters in estuaries and over continental shelves . They occupy about 8 percent of the total ocean area [ 65 ] and account for about half of all the ocean productivity. The key nutrients determining eutrophication are nitrogen in coastal waters and phosphorus in lakes. Both are found in high concentrations in guano (seabird feces), which acts as a fertilizer for the surrounding ocean or an adjacent lake. Uric acid is the dominant nitrogen compound, and during its mineralization different nitrogen forms are produced. [ 66 ]
Ecosystems, even those with seemingly distinct borders, rarely function independently of other adjacent systems. [ 67 ] Ecologists are increasingly recognizing the important effects that cross-ecosystem transport of energy and nutrients have on plant and animal populations and communities. [ 68 ] [ 69 ] A well known example of this is how seabirds concentrate marine-derived nutrients on breeding islands in the form of feces (guano) which contains ~15–20% nitrogen (N), as well as 10% phosphorus. [ 70 ] [ 71 ] [ 72 ] These nutrients dramatically alter terrestrial ecosystem functioning and dynamics and can support increased primary and secondary productivity. [ 73 ] [ 74 ] However, although many studies have demonstrated nitrogen enrichment of terrestrial components due to guano deposition across various taxonomic groups, [ 73 ] [ 75 ] [ 76 ] [ 77 ] only a few have studied its retroaction on marine ecosystems and most of these studies were restricted to temperate regions and high nutrient waters. [ 70 ] [ 78 ] [ 79 ] [ 80 ] In the tropics, coral reefs can be found adjacent to islands with large populations of breeding seabirds, and could be potentially affected by local nutrient enrichment due to the transport of seabird-derived nutrients in surrounding waters. Studies on the influence of guano on tropical marine ecosystems suggest nitrogen from guano enriches seawater and reef primary producers. [ 78 ] [ 81 ] [ 82 ]
Reef building corals have essential nitrogen needs and, thriving in nutrient-poor tropical waters [ 83 ] where nitrogen is a major limiting nutrient for primary productivity, [ 84 ] they have developed specific adaptations for conserving this element. Their establishment and maintenance are partly due to their symbiosis with unicellular dinoflagellates, Symbiodinium spp. (zooxanthellae), that can take up and retain dissolved inorganic nitrogen (ammonium and nitrate) from the surrounding waters. [ 85 ] [ 86 ] [ 87 ] These zooxanthellae can also recycle the animal wastes and subsequently transfer them back to the coral host as amino acids, [ 88 ] ammonium or urea. [ 89 ] Corals are also able to ingest nitrogen-rich sediment particles [ 90 ] [ 91 ] and plankton. [ 92 ] [ 93 ] Coastal eutrophication and excess nutrient supply can have strong impacts on corals, leading to a decrease in skeletal growth, [ 86 ] [ 94 ] [ 95 ] [ 96 ] [ 82 ]
Food web theory predicts that current global declines in marine predators could generate unwanted consequences for many marine ecosystems. In coastal plant communities, such as kelp, seagrass meadows, mangrove forests and salt marshes, several studies have documented the far-reaching effects of changing predator populations. Across coastal ecosystems, the loss of marine predators appears to negatively affect coastal plant communities and the ecosystem services they provide. [ 97 ]
The green world hypothesis predicts loss of predator control on herbivores could result in runaway consumption that would eventually denude a landscape or seascape of vegetation. [ 98 ] Since the inception of the green world hypothesis, ecologists have tried to understand the prevalence of indirect and alternating effects of predators on lower trophic levels ( trophic cascades ), and their overall impact on ecosystems. [ 99 ] Multiple lines of evidence now suggest that top predators are key to the persistence of some ecosystems. [ 99 ] [ 97 ]
With an estimated habitat loss greater than 50 percent, coastal plant communities are among the world's most endangered ecosystems. [ 100 ] [ 101 ] [ 102 ] As bleak as this number is, the predators that patrol coastal systems have fared far worse. Several predatory taxa including species of marine mammals , elasmobranchs , and seabirds have declined by 90 to 100 percent compared to historical populations. [ 11 ] [ 103 ] Predator declines pre-date habitat declines, [ 11 ] suggesting alterations to predator populations may be a major driver of change for coastal systems. [ 104 ] [ 105 ] [ 97 ]
There is little doubt that collapsing marine predator populations results from overharvesting by humans. Localized declines and extinctions of coastal predators by humans began over 40,000 years ago with subsistence harvesting. [ 106 ] However, for most large bodied, marine predators ( toothed whales , large pelagic fish , sea birds, pinnipeds , and otters ) the beginning of their sharp global declines occurred over the last century, coinciding with the expansion of coastal human populations and advances in industrial fishing . [ 11 ] [ 107 ] Following global declines in marine predators, evidence of trophic cascades in coastal ecosystems started to emerge, [ 108 ] [ 109 ] [ 110 ] [ 111 ] with the disturbing realisation that they affected more than just populations of lower trophic levels. [ 99 ] [ 97 ]
Understanding the importance of predators in coastal plant communities has been bolstered by their documented ability to influence ecosystem services. Multiple examples have shown that changes to the strength or direction of predator effects on lower trophic levels can influence coastal erosion , [ 112 ] carbon sequestration , [ 113 ] [ 114 ] and ecosystem resilience . [ 115 ] The idea that the extirpation of predators can have far-reaching effects on the persistence of coastal plants and their ecosystem services has become a major motivation for their conservation in coastal systems. [ 99 ] [ 114 ] [ 97 ]
Seascape ecology is the marine and coastal version of landscape ecology . [ 118 ] It is currently emerging as an interdisciplinary and spatially explicit ecological science with relevance to marine management, biodiversity conservation, and restoration. [ 117 ] Seascapes are complex ocean spaces, shaped by dynamic and interconnected patterns and processes operating across a range of spatial and temporal scales. [ 119 ] [ 120 ] [ 121 ] Rapid advances in geospatial technologies and the proliferation of sensors, both above and below the ocean surface, have revealed intricate and scientifically intriguing ecological patterns and processes, [ 122 ] [ 123 ] [ 124 ] some of which are the result of human activities. [ 125 ] [ 126 ] Despite progress in the collecting, mapping, and sharing of ocean data, the gap between technological advances and the ability to generate ecological insights for marine management and conservation practice remains substantial. [ 127 ] [ 128 ] For instance, fundamental gaps exist in the understanding of multidimensional spatial structure in the sea, [ 124 ] [ 121 ] [ 129 ] and the implications for planetary health and human wellbeing. [ 128 ] Deeper understanding of the multi-scale linkages between ecological structure, function, and change will better support the design of whole-system strategies for biodiversity preservation and reduce uncertainty around the consequences of human activity. For example, in the design and evaluation of marine protected areas (MPAs) and habitat restoration, it is important to understand the influence of spatial context, configuration, and connectivity, and to consider effects of scale. [ 130 ] [ 131 ] [ 132 ] [ 133 ] [ 117 ]
The diagram on the right shows the principal interactions between mangroves, seagrass, and coral reefs. [ 136 ] Coral reefs, seagrasses, and mangroves buffer habitats further inland from storms and wave damage as well as participate in a tri-system exchange of mobile fish and invertebrates. Mangroves and seagrasses are critical in regulating sediment, freshwater, and nutrient flows to coral reefs. [ 136 ]
The diagram immediately below shows locations where mangroves, coral reefs, and seagrass beds exist within one km of each other. Buffered intersection between the three systems provides relative co-occurrence rates on a global scale. Regions where systems strongly intersect include Central America (Belize), the Caribbean, the Red Sea, the Coral Triangle (particularly Malaysia), Madagascar, and the Great Barrier Reef. [ 136 ]
The diagram at the right graphically illustrates the ecosystem service synergies between mangroves, seagrasses, and coral reefs. The ecosystem services provided by intact reefs, seagrasses, and mangroves are both highly valuable and mutually enhance each other. Coastal protection (storm/wave attenuation) maintains the structure of adjacent ecosystems, and associated ecosystem services, in an offshore-to-onshore direction. Fisheries are characterized by migratory species, and therefore, protecting fisheries in one ecosystem increases fish biomass in others. Tourism benefits from coastal protection and healthy fisheries from multiple ecosystems. Here, we do not draw within-ecosystem connections in order to better emphasise synergies between systems. [ 136 ]
To compound things, removal of biomass from the ocean occurs simultaneously with multiple other stressors associated to climate change that compromise the capacity of these socio-ecological systems to respond to perturbations. [ 138 ] [ 139 ] [ 140 ] Besides sea surface temperature, climate change also affects many other physical–chemical characteristics of marine coastal waters (stratification, acidification, ventilation) [ 141 ] [ 142 ] as well as the wind regimes that control surface water productivity along the productive coastal upwelling ecosystems. [ 143 ] [ 144 ] [ 145 ] [ 146 ] [ 147 ] Changes in the productivity of the oceans are reflected in changes of plankton biomass. Plankton contributes approximately half of the global primary production, supports marine food webs, influences the biogeochemical process in the ocean, and strongly affects commercial fisheries. [ 148 ] [ 149 ] [ 150 ] Indeed, an overall decrease in marine plankton productivity is expected over global scales. [ 142 ] [ 148 ] [ 151 ] Long-term increases and decreases in plankton productivity have already occurred over the past two decades [ 152 ] [ 153 ] along extensive regions of the Humboldt upwelling ecosystem off Chile, and are expected to propagate up the pelagic and benthic food webs. [ 137 ]
Network ecology has advanced understanding of ecosystems by providing a powerful framework to analyse biological communities. [ 154 ] Previous studies used this framework to assess food web robustness against species extinctions, defined as the fraction of initial species that remain present in the ecosystem after a primary extinction. [ 155 ] [ 156 ] [ 157 ] [ 158 ] [ 159 ] [ 160 ] [ 161 ] [ 162 ] These studies showed the importance for food web persistence of highly connected species (independent of trophic position), [ 155 ] [ 158 ] [ 163 ] basal species, [ 156 ] and highly connected species that, at the same time, trophically support other highly connected species. [ 159 ] Most of these studies used a static approach, which stems from network theory and analyzes the impacts of structural changes on food webs represented by nodes (species) and links (interactions) that connect nodes, but ignores interaction strengths and population dynamics of interacting species. [ 155 ] Other studies used a dynamic approach, which considers not only the structure and intensity of interactions in a food web, but also the changes in species biomasses through time and the indirect effects that these changes have on other species. [ 156 ] [ 157 ] [ 164 ] [ 165 ] [ 166 ] [ 137 ]
Globally, eutrophication is one of the major environmental problems in coastal ecosystems. Over the last century the annual riverine inputs of nitrogen and phosphorus to the oceans have increased from 19 to 37 megatonnes of nitrogen and from 2 to 4 megatonnes of phosphorus. [ 167 ] Regionally, these increases were even more substantial as observed in the United States, Europe and China. In the Baltic Sea nitrogen and phosphorus loads increased by roughly a factor of three and six, respectively. [ 168 ] The riverine nitrogen flux has increased by an order of magnitude to coastal waters of China within thirty years, while phosphorus export has tripled between 1970 and 2000. [ 169 ] [ 170 ] [ 2 ]
Efforts to mitigate eutrophication through nutrient load reductions are hampered by the effects of climate change . [ 10 ] Changes in precipitation increase the runoff of N, P and carbon (C) from land, which together with warming and increased CO 2 dissolution alter the coupled marine nutrient and carbon cycles. [ 171 ] [ 172 ] [ 2 ]
In contrast to the open ocean where biogeochemical cycling is largely dominated by pelagic processes driven primarily by ocean circulation , in the coastal zone , pelagic and benthic processes interact strongly and are driven by a complex and dynamic physical environment. [ 173 ] Eutrophication in coastal areas leads to shifts toward rapidly growing opportunistic algae, and generally to a decline in benthic macrovegetation because of decreased light penetration, substrate change and more reducing sediments. [ 174 ] [ 175 ] Increased production and warming waters have caused expanding hypoxia at the seafloor with a consequent loss of benthic fauna . [ 176 ] [ 177 ] Hypoxic systems tend to lose many long-lived higher organisms and biogeochemical cycles typically become dominated by benthic bacterial processes and rapid pelagic turnover. [ 178 ] However, if hypoxia does not occur, benthic fauna tends to increase in biomass with eutrophication. [ 179 ] [ 180 ] [ 181 ] [ 2 ]
Changes in benthic biota have far-reaching impacts on biogeochemical cycles in the coastal zone and beyond. In the illuminated zone , benthic microphytes and macrophytes mediate biogeochemical fluxes through primary production , nutrient storage and sediment stabilization and act as a habitat and food source for a variety of animals, as shown in the diagram on the left above. Benthic animals contribute to biogeochemical transformations and fluxes between water and sediments both directly through their metabolism and indirectly by physically reworking the sediments and their porewaters and stimulating bacterial processes. Grazing on pelagic organic matter and biodeposition of feces and pseudofeces by suspension-feeding fauna increases organic matter sedimentation rates. [ 182 ] [ 183 ] In addition, nutrients and carbon are retained in biomass and transformed from organic to inorganic forms through metabolic processes. [ 184 ] [ 181 ] [ 185 ] Bioturbation , including sediment reworking and burrow ventilation activities ( bioirrigation ), redistributes particles and solutes within the sediment and enhances sediment-water fluxes of solutes. [ 186 ] [ 187 ] Bioturbation can also enhance resuspension of particles, a phenomenon termed "bioresuspension". [ 188 ] Together, all these processes affect physical and chemical conditions at the sediment-water interface, [ 189 ] and strongly influence organic matter degradation. [ 190 ] When up-scaled to the ecosystem level, such modified conditions can significantly alter the functioning of coastal ecosystems and ultimately, the role of the coastal zone in filtering and transforming nutrients and carbon. [ 2 ]
Artisanal fisheries use simple fishing gears and small vessels. [ 137 ] Their activities tend to be confined to coastal areas. In general, top-down and bottom-up forces determine ecosystem functioning and dynamics. Fisheries as a top-down force can shorten and destabilise food webs , while effects driven by climate change can alter the bottom-up forces of primary productivity . [ 137 ]
Direct human impacts and the full suite of drivers of global change are the main cause of species extinctions in Anthropocene ecosystems, [ 191 ] [ 106 ] with detrimental consequences on ecosystem functioning and their services to human societies. [ 192 ] [ 193 ] The world fisheries crisis is among those consequences, which cuts across fishing strategies, oceanic regions, species, and includes countries that have little regulation and those that have implemented rights-based co-management strategies to reduce overharvesting . [ 194 ] [ 195 ] [ 196 ] [ 197 ] [ 137 ]
Chile has been one of the countries implementing Territorial Use Rights (TURFs) [ 198 ] [ 199 ] over an unprecedented geographic scale to manage the diverse coastal benthic resources using a co-management strategy. [ 200 ] [ 201 ] These TURFS are used for artisanal fisheries. Over 60 coastal benthic species are actively harvested by these artisanal fisheries, [ 202 ] with species that are extracted from intertidal and shallow subtidal habitats. [ 203 ] [ 204 ] The Chilean TURFs system brought significant improvements in sustainability of this complex socio-ecological system, helping to rebuild benthic fish stocks , [ 202 ] [ 200 ] improving fishers’ perception towards sustainability and increasing compliance9, as well as showing positive ancillary effects on conservation of biodiversity. [ 205 ] [ 206 ] However, the situation of most artisanal fisheries is still far from sustainable, and many fish stocks and coastal ecosystems show signs of overexploitation and ecosystem degradation, a consequence of the low levels of cooperation and low enforcement of TURF regulations, which leads to high levels of free-riding and illegal fishing . [ 207 ] [ 208 ] [ 209 ] It is imperative to improve understanding of the effects of these multi-species artisanal fisheries which simultaneously harvest species at all trophic levels from kelp primary producers to top carnivores. [ 204 ] [ 210 ] [ 137 ]
Coastal zones are among the most populated areas on the planet. [ 213 ] [ 214 ] As the population continues to increase, economic development must expand to support human welfare. However, this development may damage the ability of the coastal environment to continue supporting human welfare for current and future generations. [ 215 ] The management of complex coastal and marine social-ecological systems requires tools that provide frameworks with the capability of responding to current and emergent issues. [ 216 ] [ 211 ] Remote data collection technologies include satellite-based remote sensing , aerial remote sensing , unmanned aerial vehicles , unmanned surface vehicles , unmanned underwater vehicles , and static sensors. [ 211 ]
Frameworks have been developed that attempt to address and integrate these complex issues, such as the Millennium Ecosystem Assessment framework which links drivers, ecosystem services, and human welfare [ 217 ] [ 211 ] However, obtaining the environmental data that is necessary to use such frameworks is difficult, especially in countries where access to reliable data and their dissemination are limited or non-existent [ 218 ] and even thwarted. [ 211 ] Traditional techniques of point sampling and observation in the environment do deliver high information content, [ 219 ] but they are expensive and often do not provide adequate spatial and temporal coverage, while remote sensing can provide cost-effective solutions, as well as data for locations where there is no or only limited information. [ 220 ] [ 211 ]
Coastal observing systems are typically nationally funded and built around national priorities. As a result, there are presently significant differences between countries in terms of sustainability, observing capacity and technologies, as well as methods and research priorities. [ 212 ] Ocean observing systems in coastal areas need to move toward integrated, multidisciplinary and multiscale systems , where heterogeneity can be exploited to deliver fit-for-purpose answers. [ 212 ] Essential elements of such distributed observation systems are the use of machine-to-machine communication , data fusion and processing applying recent technological developments for the Internet of Things (IoT) toward a common cyberinfrastructure . [ 212 ] It has been argued that the standardisation that IoT brings to wireless sensing will revolutionise areas like this. [ 221 ]
Coastal areas are the most dynamic and productive parts of the oceans, which makes them a significant source of human resources and services. Coastal waters are located immediately in contact with human populations and exposed to anthropogenic disturbances, placing these resources and services under threat. [ 222 ] These concerns explain why, in several coastal regions, a rapidly increasing number of observing systems have been implemented in the last decade. [ 223 ] Expansion of coherent and sustained coastal observations has been fragmented and driven by national and regional policies and is often undertaken through short-term research projects. [ 224 ] This results in significant differences between countries both in terms of sustainability and observing technologies, methods and research priorities. [ 212 ]
Unlike the open ocean, where challenges are rather well-defined and stakeholders are fewer and well-identified, coastal processes are complex, acting on several spatial and temporal scales, with numerous and diversified users and stakeholders, often with conflicting interests. To adapt to such complexity coastal ocean observing system must be an integrated, multidisciplinary and multiscale system of systems. [ 225 ] [ 212 ]
Marine ecosystems are affected by diverse pressures and consequently may undergo significant changes that can be interpreted as regime shifts . [ 226 ] Marine ecosystems worldwide are affected by increasing natural and anthropogenic pressures and consequently undergo significant changes at unprecedented rates. Affected by these changes, ecosystems can reorganise and still maintain the same function, structure, and identity. [ 227 ] However, under some circumstances, the ecosystem may undergo changes that modify the system's structure and function and this process can be described as a shift to a new regime. [ 227 ] [ 228 ] [ 229 ] [ 226 ]
Usually, a regime shift is triggered by large-scale climate-induced variations, [ 230 ] intense fishing exploitation [ 231 ] or both. [ 232 ] Criteria used to define regime shifts vary and the changes that have to occur in order to consider that a system has undergone a regime shift are not well-defined. [ 233 ] Normally, regime shifts are defined as high amplitude, low-frequency and often abrupt changes in species abundance and community composition that are observed at multiple trophic levels (TLs). [ 234 ] These changes are expected to occur on a large spatial scale and take place concurrently with physical changes in the climate system. [ 234 ] [ 229 ] [ 235 ] [ 236 ] [ 237 ] [ 238 ] [ 233 ] [ 226 ]
Regime shifts have been described in several marine ecosystems including Northern Benguela , [ 239 ] the North Sea, [ 240 ] and the Baltic Sea. [ 241 ] In large upwelling ecosystems, it is common to observe decadal fluctuations in species abundance and their replacements. [ 242 ] These fluctuations might be irreversible and might be an indicator of the new regime, as was the case in the Northern Benguela ecosystem. [ 239 ] However, changes in the upwelling systems might be interpreted as fluctuations within the limits of natural variability for an ecosystem, and not as an indicator of the regime shift. [ 235 ] The Portuguese continental shelf ecosystem (PCSE) constitutes the northernmost part of the Canary Current Upwelling System and is characterised by seasonal upwelling that occurs during the spring and summer as a result of steady northerly winds. [ 243 ] [ 244 ] It has recently changed in the abundance of coastal pelagic species such as sardine , chub mackerel , horse mackerel , blue jack mackerel and anchovy . [ 245 ] [ 246 ] [ 247 ] [ 248 ] Moreover, in the last decades, an increase in higher trophic level species has been documented. [ 249 ] The causes underlying changes in the pelagic community are not clear but it has been suggested that they result from a complex interplay between environmental variability, species interactions and fishing pressure . [ 250 ] [ 251 ] [ 252 ] [ 226 ]
There is evidence, that changes in the intensity of the Iberian coastal upwelling (resulting from the strengthening or weakening northern winds) had occurred in the last decades. However, the character of these changes is contradictory where some authors observed intensification of upwelling-favourable winds [ 253 ] [ 254 ] while others documented their weakening. [ 255 ] [ 256 ] A 2019 review of upwelling rate and intensity along the Portuguese coast documented a successive weakening of the upwelling since 1950 that lasted till mid/late 1970s in the north-west and south-west and till 1994 in the south coast. [ 257 ] An increase in upwelling index over the period 1985–2009 was documented in all studied regions while additionally upwelling intensification were observed in the south. [ 257 ] A continuous increase in water temperature, ranging from 0.1 to 0.2 °C per decade has also been documented. [ 258 ] [ 226 ]
Many marine fauna utilise coastal habitats as critical nursery areas, for shelter and feeding, yet these habitats are increasingly at risk from agriculture, aquaculture, industry and urban expansion. [ 259 ] Indeed, these systems are subject to what may be called "a triple whammy" of increasing industrialisation and urbanisation, an increased loss of biological and physical resources (fish, water, energy, space), and a decreased resilience to the consequences of a warming climate and sea level rise . [ 260 ] This has given rise to the complete loss, modification or disconnection of natural coastal ecosystems globally. For example, almost 10% of the entire Great Barrier Reef coastline in Australia (2,300 km) has been replaced with urban infrastructure (e.g., rock seawalls, jetties, marinas), causing massive loss and fragmentation of sensitive coastal ecosystems. [ 261 ] Global loss of seagrass reached around 7% of seagrasses area per year by the end of the twentieth century. [ 262 ] A global analysis of tidal wetlands ( mangroves , tidal flats , and tidal marshes ) published in 2022 estimated global losses of 13,700 km 2 (5,300 sq mi) from 1999-2019, however, this study also estimated that these losses were largely offset by the establishment of 9,700 km 2 (3,700 sq mi) of new tidal wetlands that were not present in 1999. [ 263 ] Approximately three-quarters of the 4,000 km 2 (1,500 sq mi) net decrease between 1999 and 2019 occurred in Asia (74.1%), with 68.6% concentrated in three countries: Indonesia (36%), China (20.6%), and Myanmar (12%). [ 263 ] Of these global tidal wetland losses and gains, 39% of losses and 14% of gains were attributed to direct human activities. [ 263 ]
Approximately 40% of the global mangrove has been lost since the 1950s [ 264 ] with more than 9,736 km 2 of the world's mangroves continuing to be degraded in the 20 years period between 1996 and 2016. [ 265 ] Saltmarshes are drained when coastal land is claimed for agriculture, and deforestation is an increasing threat to shoreline vegetation (such as mangroves) when coastal land is appropriated for urban and industrial development, [ 264 ] both of which may result in the degradation of blue carbon storages and increasing greenhouse gas emissions. [ 266 ]
These accumulating pressures and impacts on coastal ecosystems are neither isolated nor independent, rather they are synergistic, with feedbacks and interactions that cause individual effects to be greater than their sums. [ 267 ] In the year before the ecosystem restoration Decade commences, there is a critical knowledge deficit inhibiting an appreciation of the complexity of coastal ecosystems that hampers the development of responses to mitigate continuing impacts—not to mention uncertainty on projected losses of coastal systems for some of the worst-case future climate change scenarios. [ 268 ]
The United Nations has declared 2021–2030 the UN Decade on Ecosystem Restoration . This call to action has the purpose of recognising the need to massively accelerate global restoration of degraded ecosystems, to fight the climate heating crisis, enhance food security, provide clean water and protect biodiversity on the planet. The scale of restoration will be key. For example, the Bonn Challenge has the goal to restore 350 million km 2 , about the size of India, of degraded terrestrial ecosystems by 2030. However, international support for restoration of blue coastal ecosystems , which provide an impressive array of benefits to people, has lagged.
The diagram on the right shows the current state of modified and impacted coastal ecosystems and the expected state following the decade of restoration. [ 268 ] Also, shown is the uncertainty in the success of past restoration efforts, current state of altered systems, climate variability, and restoration actions that are available now or on the horizon. This could mean that delivering the Decade on Ecosystem Restoration for coastal systems needs to be viewed as a means of getting things going where the benefits might take longer than a decade. [ 268 ]
Only the Global Mangrove Alliance [ 269 ] comes close to the Bonn Challenge, with the aim of increasing the global area of mangroves by 20% by 2030. [ 268 ] However, mangrove scientists have reservations about this target, voicing concerns that it is unrealistic and may prompt inappropriate practices in attempting to reach this target. [ 270 ] [ 268 ]
There has recently been a perceptual shift away from habitat representation as the sole or primary focus of conservation prioritisation, towards consideration of ecological processes that shape the distribution and abundance of biodiversity features. [ 271 ] [ 272 ] [ 273 ] [ 274 ] In marine ecosystems, connectivity processes are paramount, [ 275 ] and designing systems of marine protected areas that maintain connectivity between habitat patches has long been considered an objective of conservation planning. [ 271 ] [ 276 ] Two forms of connectivity are critical to structuring coral reef fish populations: [ 277 ] dispersal of larvae in the pelagic environment, [ 278 ] and post-settlement migration by individuals across the seascape. [ 279 ] Whilst a growing literature has described approaches for considering larval connectivity in conservation prioritisation, [ 280 ] [ 281 ] [ 282 ] relatively less attention has been directed towards developing and applying methods for considering post-settlement connectivity [ 275 ] [ 283 ] [ 284 ]
Seascape connectivity (connectedness among different habitats in a seascape, cf. among patches of the same habitat type) [ 132 ] is essential for species that utilise more than one habitat, either during diurnal movements or at different stages in their life history. Mangroves, seagrass beds, and lagoon reefs provide nursery areas for many commercially and ecologically important fish species that subsequently make ontogenetic shifts to adult populations on coral reefs. [ 285 ] [ 286 ] [ 287 ] These back-reef habitats are often overlooked for conservation or management in favour of coral reefs that support greater adult biomass, yet they can be equally if not more at risk from habitat degradation and loss. [ 288 ] [ 47 ] [ 289 ] Even where juveniles are not targeted by fishers, they can be vulnerable to habitat degradation, for example from sedimentation caused by poor land-use practices. [ 290 ] [ 284 ]
There is clear empirical evidence that proximity to nursery habitats can enhance the effectiveness (i.e. increasing the abundance, density, or biomass of fish species) of marine protected areas on coral reefs. [ 132 ] [ 291 ] [ 292 ] [ 293 ] [ 294 ] For example, at study sites across the western Pacific, the abundance of harvested fish species was significantly greater on protected reefs close to mangroves, but not on protected reefs isolated from mangroves. [ 293 ] The functional role of herbivorous fish species that perform ontogenetic migrations may also enhance the resilience of coral reefs close to mangroves. [ 295 ] [ 296 ] Despite this evidence, and widespread calls to account for connectivity among habitats in the design of spatial management, [ 286 ] [ 293 ] [ 294 ] there remain few examples where seascape connectivity is explicitly considered in spatial conservation prioritisation (the analytical process of identifying priority areas for conservation or management actions). [ 284 ] | https://en.wikipedia.org/wiki/Marine_coastal_ecosystem |
Marine debris , also known as marine litter , is human-created solid material that has deliberately or accidentally been released in seas or the ocean . Floating oceanic debris tends to accumulate at the center of gyres and on coastlines , frequently washing aground, when it is known as beach litter or tidewrack. Deliberate disposal of wastes at sea is called ocean dumping . Naturally occurring debris, such as driftwood and drift seeds , are also present. With the increasing use of plastic , human influence has become an issue as many types of (petrochemical) plastics do not biodegrade quickly, as would natural or organic materials. [ 1 ] The largest single type of plastic pollution (~10%) and majority of large plastic in the oceans is discarded and lost nets from the fishing industry. [ 2 ] Waterborne plastic poses a serious threat to fish , seabirds , marine reptiles , and marine mammals , as well as to boats and coasts. [ 3 ]
Dumping, container spillages, litter washed into storm drains and waterways and wind-blown landfill waste all contribute to this problem. This increased water pollution has caused serious negative effects such as discarded fishing nets capturing animals, concentration of plastic debris in massive marine garbage patches , and increasing concentrations of contaminants in the food chain .
In efforts to prevent and mediate marine debris and pollutants, laws and policies have been adopted internationally, with the UN including reduced marine pollution in Sustainable Development Goal 14 "Life Below Water". Depending on relevance to the issues and various levels of contribution, some countries have introduced more specified protection policies. Moreover, some non-profits, NGOs, and government organizations are developing programs to collect and remove plastics from the ocean. However, in 2017 the UN estimated that by 2050 there will be more plastic than fish in the oceans if substantial measures are not taken. [ 4 ]
Researchers classify debris as either land- or ocean-based; in 1991, the United Nations Joint Group of Experts on the Scientific Aspects of Marine Pollution estimated that up to 80% of the pollution was land-based, [ 5 ] with the remaining 20% originating from catastrophic events or maritime sources. [ 6 ] More recent studies have found that more than half of plastic debris found on Korean shores is ocean-based. [ 7 ]
A wide variety of man-made objects can become marine debris; plastic bags , balloons , buoys , rope , medical waste , glass and plastic bottles , cigarette stubs , cigarette lighters , beverage cans , polystyrene , lost fishing line and nets , and various wastes from cruise ships and oil rigs are among the items commonly found to have washed ashore. Six-pack rings , in particular, are considered emblematic of the problem. [ 8 ]
The U.S. military used ocean dumping for unused weapons and bombs , including ordinary bombs , Unexploded ordnance (UXO) , landmines and chemical weapons from at least 1919 until 1970. [ 9 ] Millions of pounds of ordnance were disposed of in the Gulf of Mexico and off the coasts of at least 16 states, from New Jersey to Hawaii (although these, of course, do not wash up onshore, and the U.S. is not the only country who has practiced this). [ 10 ]
Eighty percent of marine debris is plastic. [ 11 ] Plastics accumulate because they typically do not biodegrade as many other substances do. They photodegrade on exposure to sunlight, although they do so only under dry conditions, as water inhibits photolysis . [ 12 ] In a 2014 study using computer models, scientists from the group 5 Gyres, estimated 5.25 trillion pieces of plastic weighing 269,000 tons were dispersed in oceans in similar amount in the Northern and Southern Hemispheres. [ 13 ]
Some materials and activities used in industrial activities that do not readily degrade, that persist in the environment, and tend to accumulate over time. The activities can include fishing, boating, and aquaculture industries that harvest or use resources in the marine environment and may lose or discard gear, materials, machinery or solid wastes from industrial processes into the water or onto shorelines. This can include anything as large as a fishing boat or as small as particle from a Styrofoam lobster float. In 2003, a study was conducted to identify types, amounts, sources, and effects of persistent industrial marine debris in the coastal waters and along the shores of Charlotte County, New Brunswick , and examine any relationship between the amount and types of persistent industrial marine debris, and the types and numbers of industrial operations nearby. [ 14 ] Materials like plastic or foam can break down into smaller particles and may look like small sea creatures to wildlife such as birds, cetaceans, and fish, and they may eat these particles. Indigestible material may accumulate in the gut creating blockages or a false sense of fullness and eventually death from lack of appropriate nutrient intake. [ citation needed ]
Ghost nets are fishing nets that have been abandoned, lost, or otherwise discarded in the ocean, lakes, and rivers. [ 15 ] These nets, often nearly invisible in the dim light, can be left tangled on a rocky reef or drifting in the open sea. They can entangle fish , dolphins , sea turtles , sharks , dugongs , crocodiles , seabirds , crabs , and other creatures, including the occasional human diver. [ 16 ] Acting as designed, the nets restrict movement, causing starvation, laceration and infection, and suffocation in those that need to return to the surface to breathe. [ 17 ]
A growing concern regarding plastic pollution in the marine ecosystem is the use of microplastics. Microplastics are beads of plastic less than 5 millimeters wide, [ 19 ] and they are commonly found in hand soaps, face cleansers, and other exfoliators. When these products are used, the microplastics go through the water filtration system and into the ocean, but because of their small size they are likely to escape capture by the preliminary treatment screens on wastewater plants. [ 20 ] These beads are harmful to the organisms in the ocean, especially filter feeders, because they can easily ingest the plastic and become sick. The microplastics are such a concern because it is difficult to clean them up due to their size, so humans can try to avoid using these harmful plastics by purchasing products that use environmentally safe exfoliates.
Marine debris is found on the floor of the Arctic ocean. [ 23 ] Although an increasing number of studies have been focused on plastic debris accumulation on the coasts, in off-shore surface waters, and that ingested by marine organisms that live in the upper levels of the water column, there is limited information on debris in the mesopelagic and deeper layers. [ 24 ] Studies that have been done have conducted research through bottom sampling, video observation via remotely operated vehicles (ROVs), and submersibles. They are also mostly limited to one-off projects that do not extend long enough to show significant effects of deep-sea debris over time. Research thus far has shown that debris in the deep-ocean is in fact impacted by anthropogenic activities, and plastic has been frequently observed in the deep-sea, especially in areas off-shore of heavily populated regions, such as the Mediterranean. [ 24 ]
Litter, made from diverse materials that are lighter than surface water (such as glasses , metals and some plastics), have been found to spread over the floor of seas and open oceans, where it can become entangled in corals and interfere with other sea-floor life , or even become buried under sediment, making clean-up extremely difficult, especially due to the wide area of its dispersal compared to shipwrecks . [ 25 ] Plastics that are usually negatively buoyant can sink with the adherence of phytoplankton and the aggregation of other organic particles. Other oceanic processes that affect circulation, such as coastal storms and offshore convection, play a part in transferring large volumes of particles and debris. Submarine topographic features can also augment downwelling currents, leading to the retention of microplastics at certain locations. [ 26 ]
A Deep-sea Debris database by the Global Oceanographic Data Center of the Japan Agency for Marine-Earth Science and Technology (JAMSTEC), showing thirty years of photos and samples of marine debris since 1983, was made public in 2017. From the 5,010 dives in the database, using both ROVs and deep-sea submersibles, 3,425 man-made debris items were counted. [ 24 ] The two most significant types of debris were macro-plastic, making up 33% of the debris found – 89% of which was single-use – and metal, making up 26%. Plastic debris was found at the bottom of the Mariana Trench, at a depth of 10,898m, and plastic bags were found entangled in hydrothermal vent and cold seep communities. [ 24 ]
The 10 largest emitters of oceanic plastic pollution worldwide are, from the most to the least, China, Indonesia, Philippines, Vietnam, Sri Lanka, Thailand, Egypt, Malaysia, Nigeria, and Bangladesh, [ 27 ] largely through the rivers Yangtze, Indus, Yellow, Hai, Nile, Ganges, Pearl, Amur, Niger, and the Mekong, and accounting for "90 percent of all the plastic that reaches the world's oceans." [ 28 ] [ 29 ]
An estimated 10,000 containers at sea each year are lost by container ships , usually during storms. [ 30 ] One spillage occurred in the Pacific Ocean in 1992, when thousands of rubber ducks and other toys (now known as the "Friendly Floatees") went overboard during a storm. The toys have since been found all over the world, providing a better understanding of ocean currents . Similar incidents have happened before, such as when Hansa Carrier dropped 21 containers (with one notably containing buoyant Nike shoes). [ 31 ]
In 2007, MSC Napoli beached in the English Channel , dropping hundreds of containers, most of which washed up on the Jurassic Coast , a World Heritage Site . [ 32 ] A 2021 study following a 2014 loss of a container carrying printer cartridges calculated that some cartridges had dispersed at an average speed of between 6 cm and 13 cm per second. [ 33 ] A 1997 accident of Tokio Express ship off the British coast resulted in loss of cargo container holding 5 million Lego pieces. Some of the pieces became valued among collectors who searched the beaches for Lego dragons. It also provided valuable insight in studying marine plastic degradation. [ 34 ]
In Halifax Harbour, Nova Scotia, 52% of items were generated by recreational use of an urban park, 14% from sewage disposal and only 7% from shipping and fishing activities. [ 35 ] Around four-fifths [ 36 ] of oceanic debris is from rubbish blown onto the water from landfills , and urban runoff . [ 3 ]
Some studies show that marine debris may be dominant in particular locations. For example, a 2016 study of Aruba found that debris found the windward side of the island was predominantly marine debris from distant sources. [ 37 ] In 2013, debris from six beaches in Korea was collected and analyzed: 56% was found to be "ocean-based" and 44% "land-based". [ 38 ]
In the 1987 Syringe Tide , medical waste washed ashore in New Jersey after having been blown from Fresh Kills Landfill . [ 39 ] [ 40 ] On the remote sub-Antarctic island of South Georgia , fishing-related debris, approximately 80% plastics, are responsible for the entanglement of large numbers of Antarctic fur seals . [ 41 ]
Thirteen companies have an individual contribution of 1% or more of the total branded plastic observed in the audit events: The Coca-Cola Company, PepsiCo, Nestlé, Danone, Altria, Bakhresa Group, Wings, Unilever, Mayora Indah, Mondelez International, Mars, Incorporated, Salim Group, and British American Tobacco. All 13 companies produce food, beverage, or tobacco products. The top company, The Coca-Cola Company, was responsible for 11% (CI95% = 10 to 12%), significantly greater than any other company. The top 5 companies were responsible for 24% of the branded plastic; 56 companies were responsible for greater than 50% of the branded plastic; and 19,586 companies were responsible for all of the branded plastic. The contributions of the top companies may be an underestimation because there were brands that were not attributed to a company, and there were many unbranded objects. [ 42 ]
Not all anthropogenic artifacts placed in the oceans are harmful. Iron and concrete structures typically do little damage to the environment because they generally sink to the bottom and become immobile, and at shallow depths they can even provide scaffolding for artificial reefs . Ships and subway cars have been deliberately sunk for that purpose. [ 43 ]
Additionally, hermit crabs have been known to use pieces of beach litter as a shell when they cannot find an actual seashell of the size they need. [ 44 ]
Many animals that live on or in the sea consume flotsam by mistake, as it often looks similar to their natural prey. [ 45 ] Overall, 1288 marine species are known to ingest plastic debris, with fish making up the largest fraction. [ 46 ] Bulky plastic debris may become permanently lodged in the digestive tracts of these animals, blocking the passage of food and causing death through starvation or infection. [ 47 ] Tiny floating plastic particles also resemble zooplankton , which can lead filter feeders to consume them and cause them to enter the ocean food chain . In addition, plastic in the marine environment that contaminates the food chain can have repercussions on the viability of fish and shellfish species. [ 48 ]
In Kenya, the COVID-19 pandemic has impacted the amount of marine debris found on beaches with around 55% being a pandemic-related trash items. Although the pandemic-related trash has shown up along the beaches of Kenya, it has not made its way into the water. The reduction of litter in the ocean could be a result of the closing of beaches and lack of movement during the pandemic, so less trash was likely to end up in the ocean. [ 49 ] Additional impacts of the COVID-19 pandemic have been seen in Hong Kong, where disposable masks have ended up along the beaches of Soko’s islands. [ 50 ] This may be attributed to the increased production of medical products (masks and gloves) during the pandemic, leading to a rise in unconventional disposal of these products. [ 51 ]
Techniques for collecting and removing marine (or riverine) debris include the use of debris skimmer boats (pictured) . Devices such as these can be used where floating debris presents a danger to navigation. For example, the US Army Corps of Engineers removes 90 tons of "drifting material" from San Francisco Bay every month. The Corps has been doing this work since 1942, when a seaplane carrying Admiral Chester W. Nimitz collided with a piece of floating debris and sank, costing the life of its pilot. [ 52 ] The Ocean cleanup has also created a vessel for cleaning up riverine debris, called Interceptor . Once debris becomes "beach litter", collection by hand and specialized beach-cleaning machines are used to gather the debris. [ citation needed ]
There are also projects that stimulate fishing boats to remove any litter they accidentally fish up while fishing for fish. [ 53 ]
Elsewhere, "trash traps" are installed on small rivers to capture waterborne debris before it reaches the sea. For example, South Australia 's Adelaide operates a number of such traps, known as "trash racks" or "gross pollutant traps" on the Torrens River , which flows (during the wet season) into Gulf St Vincent . [ 54 ]
In lakes or near the coast, manual removal can also be used. Project AWARE for example promotes the idea of letting dive clubs clean up litter, for example as a diving exercise. [ 55 ]
Once a year there is a diving marine debris removal operation in Scapa Flow in Orkney , run by Ghost Fishing UK, funded by World Animal Protection and Fat Face Foundation. [ 56 ] [ 57 ] [ 58 ]
Cleanup of marine debris can be stymied by inadequate collaboration across levels of government, and a patchwork of regulatory authorities (responsibility often differs for the ocean surface, the seabed, and the shore). [ 59 ] For example, there are an estimated 1600 abandoned and derelict boats in the waters of British Columbia. [ 60 ] In 2019 Canada's federal government passed legislation to make it illegal to abandon a vessel [ 61 ] but enforcement is hampered because it is often difficult to determine who owns an abandoned boat since owners are not required to have a license – licensing is a provincial government responsibility. [ 59 ] The Victoria-based non-profit Dead Boats Disposal Society notes that lack of enforcement means abandoned boats are often left to sink, which increases the cleanup cost and compounds the environmental hazard (due to seepage of fuel, oil, plastics, and other pollutants). [ 62 ]
On the sea, the removal of artificial debris (i.e. plastics) is still in its infancy. However, some projects have been started which used ships with nets (Ocean Voyages Institute/Kaisei 2009 & 2010 and New Horizon 2009) to catch some plastics, primarily for research purposes. There is also Bluebird Marine System's SeaVax which was solar- and wind-powered and had an onboard shredder and cargo hold. [ 63 ] [ 64 ] The Sea Cleaners' Manta ship is similar in concept. [ 65 ]
Another method to gather artificial litter has been proposed by The Ocean Cleanup 's Boyan Slat . He suggested using platforms with arms to gather the debris, situated inside the current of gyres. [ 66 ] The SAS Ocean Phoenix ship is somewhat similar in design. [ 67 ] [ 68 ]
In June 2019, Ocean Voyages Institute , conducted a cleanup utilizing GPS trackers and existing maritime equipment in the North Pacific Subtropical Convergence Zone setting the record for the largest mid-ocean cleanup accomplished in the North Pacific Gyre and removed over 84,000 pounds of polymer nets and consumer plastic trash from the ocean. [ 69 ] [ 70 ]
In May/June 2020, Ocean Voyages Institute conducted a cleanup expedition in the Gyre and set a new record for the largest mid-ocean cleanup accomplished in the North Pacific Gyre which removed over 170 tons (340,000 pounds) of consumer plastics and ghostnets from the ocean. [ 71 ] [ 72 ] Utilizing custom designed GPS satellite trackers which are deployed by vessels of opportunity , Ocean Voyages Institute is able to accurately track and send cleanup vessels to remove ghostnets. The GPS Tracker technology is being combined with satellite imagery increasing the ability to locate plastic trash and ghostnets in real time via satellite imagery which will greatly increase cleanup capacity and efficiency. [ 73 ] [ 74 ]
Another issue is that removing marine debris from the ocean can potentially cause more harm than good. Cleaning up microplastics could also accidentally take out plankton, which are the main lower level food group for the marine food chain and over half of the photosynthesis on earth. [ 75 ] One of the most efficient and cost effective ways to help reduce the amount of plastic entering our oceans is to not participate in using single-use plastics, avoid plastic bottled drinks such as water bottles, use reusable shopping bags, and to buy products with reusable packaging . [ 76 ]
The ocean is a global common , so negative externalities of marine debris are not usually experienced by the producer. In the 1950s, the importance of government intervention with marine pollution protocol was recognized at the First Conference on the Law of the Sea. [ 77 ]
Ocean dumping is controlled by international law , including:
One of the earliest anti-dumping laws was Australia's Beaches, Fishing Grounds and Sea Routes Protection Act 1932 , which prohibited the discharge of "garbage, rubbish, ashes or organic refuse" from "any vessel in Australian waters" without prior written permission from the federal government. It also required permission for scuttling . [ 82 ] The act was passed in response to large amounts of garbage washing up on the beaches of Sydney and Newcastle from vessels outside the reach of local governments and the New South Wales government. [ 83 ] It was repealed and replaced by the Environment Protection (Sea Dumping) Act 1981 , which gave effect to the London Convention. [ 84 ]
In 1972 and 1974, conventions were held in Oslo and Paris respectively, and resulted in the passing of the OSPAR Convention , an international treaty controlling marine pollution in the north-east Atlantic Ocean . [ 85 ] The Barcelona Convention protects the Mediterranean Sea . The Water Framework Directive of 2000 is a European Union directive committing EU member states to free inland and coastal waters from human influence. [ 86 ] In the United Kingdom, the Marine and Coastal Access Act 2009 is designed to "ensure clean healthy, safe, productive and biologically diverse oceans and seas, by putting in place better systems for delivering sustainable development of marine and coastal environment". [ 87 ] In 2019, the EU parliament voted for an EU-wide ban on single-use plastic products such as plastic straws, cutlery, plates, and drink containers, polystyrene food and drink containers, plastic drink stirrers and plastic carrier bags and cotton buds. The law will take effect in 2021. [ 88 ]
In the waters of the United States, there have been many observed consequences of pollution including: hypoxic zones , harmful agal blooms, and threatened species. [ 89 ] In 1972, the United States Congress passed the Ocean Dumping Act , giving the Environmental Protection Agency power to monitor and regulate the dumping of sewage sludge, industrial waste, radioactive waste and biohazardous materials into the nation's territorial waters. [ 90 ] The Act was amended sixteen years later to include medical wastes . [ 91 ] It is illegal to dispose of any plastic in US waters. [ 3 ]
Property law , admiralty law and the law of the sea may be of relevance when lost, mislaid, and abandoned property is found at sea. Salvage law rewards salvors for risking life and property to rescue the property of another from peril. On land the distinction between deliberate and accidental loss led to the concept of a " treasure trove ". In the United Kingdom , shipwrecked goods should be reported to a Receiver of Wreck , and if identifiable, they should be returned to their rightful owner. [ 92 ]
A large number of groups and individuals are active in preventing or educating about marine debris. For example, 5 Gyres is an organization aimed at reducing plastics pollution in the oceans, and was one of two organizations that recently researched the Great Pacific Garbage Patch . Heal the Bay is another organization, focusing on protecting California 's Santa Monica Bay , by sponsoring beach cleanup programs along with other activities. Marina DeBris is an artist focusing most of her recent work on educating people about beach trash.
Interactive sites like Adrift [ 93 ] demonstrate where marine plastic is carried, over time, on the worlds ocean currents.
On 11 April 2013 in order to create awareness, artist Maria Cristina Finucci founded the Garbage Patch State at UNESCO –Paris in front of Director General Irina Bokova . [ 94 ] First of a series of events under the patronage of UNESCO and of Italian Ministry of the Environment. [ 95 ]
Forty-eight plastics manufacturers from 25 countries, are members of the Global Plastic Associations for solutions on Marine Litter, have made the pledge to help prevent marine debris and to encourage recycling. [ 75 ]
Marine debris is a widespread problem, not only the result of activities in coastal regions. [ 96 ]
Plastic debris from inland states come from two main sources: ordinary litter and materials from open dumps and landfills that blow or wash away to inland waterways and wastewater outflows. The refuse finds its way from inland waterways, rivers, streams and lakes to the ocean. Though ocean and coastal area cleanups are important, it is crucial to address plastic waste that originates from inland and landlocked states. [ 97 ] [ 98 ]
At the systems level, there are various ways to reduce the amount of debris entering our waterways:
Consumers can help to reduce the amount of plastic entering waterways by reducing usage of single-use plastics, avoiding microbeads, participate in a river or lake beach cleanup. [ 98 ]
Media related to Marine debris at Wikimedia Commons | https://en.wikipedia.org/wiki/Marine_debris |
A marine ecoregion is an ecoregion , or ecological region, of the oceans and seas identified and defined based on biogeographic characteristics.
A more complete definition describes them as “Areas of relatively homogeneous species composition , clearly distinct from adjacent systems” dominated by “a small number of ecosystems and/or a distinct suite of oceanographic or topographic features”. Ecologically they “are strongly cohesive units, sufficiently large to encompass ecological or life history processes for most sedentary species.” [ 1 ]
The global classification system Marine Ecoregions of the World—MEOW was devised by an international team, including major conservation organizations, academic institutions and intergovernmental organizations. [ 1 ] The system covers coastal and continental shelf waters of the world, and does not include deep ocean waters. The MEOW system integrated the biogeographic regionalization systems in use at national or continental scale, like Australia's Integrated Marine and Coastal Regionalisation of Australia and the Nature Conservancy’s system in the Americas, although it often uses different names for the subdivisions. [ 1 ]
This system has a strong biogeographic basis, but was designed to aid in conservation activities for marine ecosystems . Its subdivisions include both the seafloor ( benthic ) and shelf pelagic ( neritic ) biotas of each marine region. [ 1 ]
The digital ecoregions layer is available for download as an ArcGIS Shapefile. [ 2 ]
The Marine Ecoregions of the World classification defines 232 marine ecoregions (e.g. Adriatic Sea , Cortezian , Ningaloo , Ross Sea ) for the coastal and shelf waters of the world.
These marine ecoregions form part of a nested system and are grouped into 62 provinces (e.g. the South China Sea , Mediterranean Sea , Central Indian Ocean Islands ).
The provinces in turn, are grouped into 12 major realms. The latter are considered analogous to the eight terrestrial realms , represent large regions of the ocean basins:
Other classifications of marine ecoregions or equivalent areas have been widely developed at national and regional levels, as well as a small number of global schemes.
Each of these systems, along with numerous regional biogeographic classifications, was used to inform the MEOW system. The WWF Global 200 work also identifies a number of major habitat types that correspond to the terrestrial biomes : polar, temperate shelves and seas, temperate upwelling, tropical upwelling, tropical coral, pelagic (trades and westerlies), abyssal, and hadal (ocean trench).
One of the most comprehensive early classifications was the system of 53 coastal provinces developed by Briggs in 1974. [ 3 ] The near-global system of 64 large marine ecosystems has a partial biogeographic basis.
The World Wildlife Fund —WWF identified 43 priority marine ecoregions , as part of its Global 200 initiative. [ 4 ] | https://en.wikipedia.org/wiki/Marine_ecoregion |
Marine ecosystems are the largest of Earth 's aquatic ecosystems and exist in waters that have a high salt content. These systems contrast with freshwater ecosystems , which have a lower salt content. Marine waters cover more than 70% of the surface of the Earth and account for more than 97% of Earth's water supply [ 1 ] [ 2 ] and 90% of habitable space on Earth. [ 3 ] Seawater has an average salinity of 35 parts per thousand of water. Actual salinity varies among different marine ecosystems. [ 4 ] Marine ecosystems can be divided into many zones depending upon water depth and shoreline features. The oceanic zone is the vast open part of the ocean where animals such as whales, sharks, and tuna live. The benthic zone consists of substrates below water where many invertebrates live. The intertidal zone is the area between high and low tides. Other near-shore (neritic) zones can include mudflats , seagrass meadows , mangroves , rocky intertidal systems , salt marshes , coral reefs , kelp forests and lagoons . In the deep water, hydrothermal vents may occur where chemosynthetic sulfur bacteria form the base of the food web.
Marine ecosystems are characterized by the biological community of organisms that they are associated with and their physical environment . Classes of organisms found in marine ecosystems include brown algae , dinoflagellates , corals , cephalopods , echinoderms , and sharks .
Marine ecosystems are important sources of ecosystem services and food and jobs for significant portions of the global population . Human uses of marine ecosystems and pollution in marine ecosystems are significantly threats to the stability of these ecosystems. Environmental problems concerning marine ecosystems include unsustainable exploitation of marine resources (for example overfishing of certain species), marine pollution , climate change , and building on coastal areas. Moreover, much of the carbon dioxide causing global warming and heat captured by global warming are absorbed by the ocean, ocean chemistry is changing through processes like ocean acidification which in turn threatens marine ecosystems.
Because of the opportunities in marine ecosystems for humans and the threats created by humans, the international community has prioritized "Life below water" as Sustainable Development Goal 14 . [ 5 ] The goal is to "Conserve and sustainably use the oceans , seas and marine resources for sustainable development". [ 6 ]
Coral reefs are one of the most well-known marine ecosystems in the world, with the largest being the Great Barrier Reef . These reefs are composed of large coral colonies of a variety of species living together. The corals form multiple symbiotic relationships with the organisms around them. [ 7 ]
Mangroves are trees or shrubs that grow in low-oxygen soil near coastlines in tropical or subtropical latitudes. [ 8 ] They are an extremely productive and complex ecosystem that connects the land and sea. Mangroves consist of species that are not necessarily related to each other and are often grouped for the characteristics they share rather than genetic similarity. [ 9 ] Because of their proximity to the coast, they have all developed adaptions such as salt excretion and root aeration to live in salty, oxygen-depleted water. [ 9 ] Mangroves can often be recognized by their dense tangle of roots that act to protect the coast by reducing erosion from storm surges, currents, wave, and tides. [ 8 ] The mangrove ecosystem is also an important source of food for many species as well as excellent at sequestering carbon dioxide from the atmosphere with global mangrove carbon storage is estimated at 34 million metric tons per year. [ 9 ]
Seagrasses form dense underwater meadows which are among the most productive ecosystems in the world. They provide habitats and food for a diversity of marine life comparable to coral reefs. This includes invertebrates like shrimp and crabs, cod and flatfish, marine mammals and birds. They provide refuges for endangered species such as seahorses, turtles, and dugongs . They function as nursery habitats for shrimps, scallops and many commercial fish species. Seagrass meadows provide coastal storm protection by the way their leaves absorb energy from waves as they hit the coast. They keep coastal waters healthy by absorbing bacteria and nutrients, and slow the speed of climate change by sequestering carbon dioxide into the sediment of the ocean floor.
Seagrasses evolved from marine algae which colonized land and became land plants, and then returned to the ocean about 100 million years ago. However, today seagrass meadows are being damaged by human activities such as pollution from land runoff, fishing boats that drag dredges or trawls across the meadows uprooting the grass, and overfishing which unbalances the ecosystem. Seagrass meadows are currently being destroyed at a rate of about two football fields every hour [ citation needed ] .
Kelp forests occur worldwide throughout temperate and polar coastal oceans. [ 10 ] In 2007, kelp forests were also discovered in tropical waters near Ecuador . [ 11 ]
Physically formed by brown macroalgae , kelp forests provide a unique habitat for marine organisms [ 12 ] and are a source for understanding many ecological processes. Over the last century, they have been the focus of extensive research, particularly in trophic ecology, and continue to provoke important ideas that are relevant beyond this unique ecosystem. For example, kelp forests can influence coastal oceanographic patterns [ 13 ] and provide many ecosystem services . [ 14 ]
However, the influence of humans has often contributed to kelp forest degradation . Of particular concern are the effects of overfishing nearshore ecosystems, which can release herbivores from their normal population regulation and result in the overgrazing of kelp and other algae. [ 15 ] This can rapidly result in transitions to barren landscapes where relatively few species persist. [ 16 ] [ 17 ] Already due to the combined effects of overfishing and climate change , kelp forests have all but disappeared in many especially vulnerable places, such as Tasmania 's east coast and the coast of Northern California . [ 18 ] [ 19 ] The implementation of marine protected areas is one management strategy useful for addressing such issues, since it may limit the impacts of fishing and buffer the ecosystem from additive effects of other environmental stressors.
Estuaries occur where there is a noticeable change in salinity between saltwater and freshwater sources. This is typically found where rivers meet the ocean or sea. The wildlife found within estuaries is unique as the water in these areas is brackish - a mix of freshwater flowing to the ocean and salty seawater. [ 20 ] Other types of estuaries also exist and have similar characteristics as traditional brackish estuaries. The Great Lakes are a prime example. There, river water mixes with lake water and creates freshwater estuaries. [ 20 ] Estuaries are extremely productive ecosystems that many humans and animal species rely on for various activities. [ 21 ] This can be seen as, of the 32 largest cities in the world, 22 are located on estuaries as they provide many environmental and economic benefits such as crucial habitat for many species, and being economic hubs for many coastal communities. [ 21 ] Estuaries also provide essential ecosystem services such as water filtration, habitat protection, erosion control, gas regulation nutrient cycling, and it even gives education, recreation and tourism opportunities to people. [ 22 ]
Lagoons are areas that are separated from larger water by natural barriers such as coral reefs or sandbars. There are two types of lagoons, coastal and oceanic/atoll lagoons. [ 23 ] A coastal lagoon is, as the definition above, simply a body of water that is separated from the ocean by a barrier. An atoll lagoon is a circular coral reef or several coral islands that surround a lagoon. Atoll lagoons are often much deeper than coastal lagoons. [ 24 ] Most lagoons are very shallow meaning that they are greatly affected by changed in precipitation, evaporation and wind. This means that salinity and temperature are widely varied in lagoons and that they can have water that ranges from fresh to hypersaline. [ 24 ] Lagoons can be found in on coasts all over the world, on every continent except Antarctica and is an extremely diverse habitat being home to a wide array of species including birds, fish, crabs, plankton and more. [ 24 ] Lagoons are also important to the economy as they provide a wide array of ecosystem services in addition to being the home of so many different species. Some of these services include fisheries, nutrient cycling, flood protection, water filtration, and even human tradition. [ 24 ]
Salt marshes are a transition from the ocean to the land, where fresh and saltwater mix. [ 25 ] The soil in these marshes is often made up of mud and a layer of organic material called peat. Peat is characterized as waterlogged and root-filled decomposing plant matter that often causes low oxygen levels (hypoxia). These hypoxic conditions causes growth of the bacteria that also gives salt marshes the sulfurous smell they are often known for. [ 26 ] Salt marshes exist around the world and are needed for healthy ecosystems and a healthy economy. They are extremely productive ecosystems and they provide essential services for more than 75 percent of fishery species and protect shorelines from erosion and flooding. [ 26 ] Salt marshes can be generally divided into the high marsh, low marsh, and the upland border. The low marsh is closer to the ocean, with it being flooded at nearly every tide except low tide. [ 25 ] The high marsh is located between the low marsh and the upland border and it usually only flooded when higher than usual tides are present. [ 25 ] The upland border is the freshwater edge of the marsh and is usually located at elevations slightly higher than the high marsh. This region is usually only flooded under extreme weather conditions and experiences much less waterlogged conditions and salt stress than other areas of the marsh. [ 25 ]
Intertidal zones are the areas that are visible and exposed to air during low tide and covered up by saltwater during high tide. [ 27 ] There are four physical divisions of the intertidal zone with each one having its distinct characteristics and wildlife. These divisions are the Spray zone, High intertidal zone, Middle Intertidal zone, and Low intertidal zone. The Spray zone is a damp area that is usually only reached by the ocean and submerged only under high tides or storms. The high intertidal zone is submerged at high tide but remains dry for long periods between high tides. [ 27 ] Due to the large variance of conditions possible in this region, it is inhabited by resilient wildlife that can withstand these changes such as barnacles, marine snails, mussels and hermit crabs. [ 27 ] Tides flow over the middle intertidal zone two times a day and this zone has a larger variety of wildlife. [ 27 ] The low intertidal zone is submerged nearly all the time except during the lowest tides and life is more abundant here due to the protection that the water gives. [ 27 ]
Organisms that live freely at the surface, termed neuston , include keystone organisms like the golden seaweed Sargassum that makes up the Sargasso Sea , floating barnacles , marine snails , nudibranchs , and cnidarians . Many ecologically and economically important fish species live as or rely upon neuston. Species at the surface are not distributed uniformly; the ocean's surface harbours unique neustonic communities and ecoregions found at only certain latitudes and only in specific ocean basins. But the surface is also on the front line of climate change and pollution. Life on the ocean's surface connects worlds. From shallow waters to the deep sea, the open ocean to rivers and lakes, numerous terrestrial and marine species depend on the surface ecosystem and the organisms found there. [ 28 ]
The ocean's surface acts like a skin between the atmosphere above and the water below, and harbours an ecosystem unique to this environment. This sun-drenched habitat can be defined as roughly one metre in depth, as nearly half of UV-B is attenuated within this first meter. [ 29 ] Organisms here must contend with wave action and unique chemical [ 30 ] [ 31 ] [ 32 ] and physical properties. [ 33 ] The surface is utilised by a wide range of species, from various fish and cetaceans , to species that ride on ocean debris (termed rafters ). [ 34 ] [ 35 ] [ 36 ] Most prominently, the surface is home to a unique community of free-living organisms, termed neuston (from the Greek word, υεω, which means both to swim and to float. Floating organisms are also sometimes referred to as pleuston , though neuston is more commonly used). Despite the diversity and importance of the ocean's surface in connecting disparate habitats, and the risks it faces, not a lot is known about neustonic life. [ 28 ]
A stream of airborne microorganisms circles the planet above weather systems but below commercial air lanes. [ 37 ] Some peripatetic microorganisms are swept up from terrestrial dust storms, but most originate from marine microorganisms in sea spray . In 2018, scientists reported that hundreds of millions of viruses and tens of millions of bacteria are deposited daily on every square meter around the planet. [ 38 ] [ 39 ]
The deep sea contains up to 95% of the space occupied by living organisms. [ 40 ] Combined with the sea floor (or benthic zone), these two areas have yet to be fully explored and have their organisms documented. [ 40 ] [ 41 ]
In 1984, National Oceanic and Atmospheric Administration (NOAA) of the United States developed the concept of large marine ecosystems (sometimes abbreviated to LMEs), to identify areas of the oceans for environmental conservation purposes and to enable collaborative ecosystem-based management in transnational areas, in a way consistent with the 1982 UN Convention on the Law of the Sea . This name refers to relatively large regions on the order of 200,000 km 2 (77,000 sq mi) or greater, characterized by their distinct bathymetry , hydrography , productivity , and trophically dependent populations . Such LMEs encompass coastal areas from river basins and estuaries to the seaward boundaries of continental shelves and the outer margins of the major ocean current systems. [ 42 ]
Altogether, there are 66 LMEs, which contribute an estimated $3 trillion annually. This includes being responsible for 90% of global annual marine fishery biomass . [ 43 ] LME-based conservation is based on recognition that the world's coastal ocean waters are degraded by unsustainable fishing practices, habitat degradation , eutrophication , toxic pollution, aerosol contamination, and emerging diseases, and that positive actions to mitigate these threats require coordinated actions by governments and civil society to recover depleted fish populations, restore degraded habitats and reduce coastal pollution. Five modules are considered when assessing LMEs: productivity, fish and fisheries, pollution and ecosystem health , socioeconomics, and governance. [ 44 ] Periodically assessing the state of each module within a marine LME is encouraged to ensure maintained health of the ecosystem and future benefit to managing governments. [ 45 ] The Global Environment Facility (GEF) aids in managing LMEs off the coasts of Africa and Asia by creating resource management agreements between environmental, fisheries, energy and tourism ministers of bordering countries. This means participating countries share knowledge and resources pertaining to local LMEs to promote longevity and recovery of fisheries and other industries dependent upon LMEs. [ 46 ]
Large marine ecosystems include:
In addition to providing many benefits to the natural world, marine ecosystems also provide social, economic, and biological ecosystem services to humans. Pelagic marine systems regulate the global climate, contribute to the water cycle , maintain biodiversity, provide food and energy resources, and create opportunities for recreation and tourism. [ 48 ] Economically, marine systems support billions of dollars worth of capture fisheries, aquaculture, offshore oil and gas, and trade and shipping.
Ecosystem services fall into multiple categories, including supporting services, provisioning services, regulating services, and cultural services. [ 49 ]
The productivity of a marine ecosystem can be measured in several ways. Measurements pertaining to zooplankton biodiversity and species composition , zooplankton biomass, water-column structure, photosynthetically active radiation, transparency, chlorophyll-a, nitrate, and primary production are used to assess changes in LME productivity and potential fisheries yield. [ 50 ] Sensors attached to the bottom of ships or deployed on floats can measure these metrics and be used to quantitatively describe changes in productivity alongside physical changes in the water column such as temperature and salinity. [ 51 ] [ 52 ] [ 53 ] This data can be used in conjunction with satellite measurements of chlorophyll and sea surface temperatures to validate measurements and observe trends on greater spatial and temporal scales.
Bottom-trawl surveys and pelagic-species acoustic surveys are used to assess changes in fish biodiversity and abundance in LMEs. Fish populations can be surveyed for stock identification, length, stomach content, age-growth relationships, fecundity, coastal pollution and associated pathological conditions, as well as multispecies trophic relationships. Fish trawls can also collect sediment and inform us about ocean-bottom conditions such as anoxia . [ 54 ]
Human activities affect marine life and marine habitats through overfishing , habitat loss , the introduction of invasive species , ocean pollution , ocean acidification and ocean warming . These impact marine ecosystems and food webs and may result in consequences as yet unrecognised for the biodiversity and continuation of marine life forms. [ 58 ]
The ocean can be described as the world's largest ecosystem and it is home for many species of marine life. Different activities carried out and caused by human beings such as global warming, ocean acidification, and pollution affect marine life and its habitats. For the past 50 years, more than 90 percent of global warming resulting from human activity has been absorbed into the ocean. This results in the rise of ocean temperatures and ocean acidification which is harmful to many fish species and causes damage to habitats such as coral . [ 59 ] With coral producing materials such as carbonate rock and calcareous sediment, this creates a unique and valuable ecosystem not only providing food/homes for marine creatures but also having many benefits for humans too. Ocean acidification caused by rising levels of carbon dioxide leads to coral bleaching where the rates of calcification is lowered affecting coral growth. [ 60 ] Additionally, another issue caused by humans which impacts marine life is marine plastic pollution , which poses a threat to marine life. [ 61 ] According to the IPCC (2019), since 1950 "many marine species across various groups have undergone shifts in geographical range and seasonal activities in response to ocean warming, sea ice change and biogeochemical changes, such as oxygen loss, to their habitats." [ 62 ]
Coastal marine ecosystems experience growing population pressures with nearly 40% of people in the world living within 100 km of the coast. [ 64 ] Humans often aggregate near coastal habitats to take advantage of ecosystem services. For example, coastal capture fisheries from mangroves and coral reef habitats are estimated to be worth a minimum of $34 billion per year. [ 64 ] Yet, many of these habitats are either marginally protected or not protected. Mangrove area has declined worldwide by more than one-third since 1950, [ 65 ] and 60% of the world's coral reefs are now immediately or directly threatened. [ 66 ] [ 67 ] Human development, aquaculture, and industrialization often lead to the destruction, replacement, or degradation of coastal habitats. [ 64 ]
Moving offshore, pelagic marine systems are directly threatened by overfishing . [ 68 ] [ 69 ] Global fisheries landings peaked in the late 1980s, but are now declining, despite increasing fishing effort . [ 48 ] Fish biomass and average trophic level of fisheries landing are decreasing, leading to declines in marine biodiversity. In particular, local extinctions have led to declines in large, long-lived, slow-growing species, and those that have narrow geographic ranges. [ 48 ] Biodiversity declines can lead to associated declines in ecosystem services. A long-term study reports the decline of 74–92% of catch per unit effort of sharks in Australian coastline from the 1960s to 2010s. [ 70 ] Such biodiversity losses impact not just species themselves, but humans as well, and can contribute to climate change across the globe. The National Oceanic and Atmospheric Administration (NOAA) states that managing and protecting marine ecosystems is crucial in attempting to conserve biodiversity in the face of Earth’s rapidly changing climate. [ 71 ]
Marine pollution occurs when substances used or spread by humans, such as industrial , agricultural , and residential waste ; particles ; noise ; excess carbon dioxide ; or invasive organisms enter the ocean and cause harmful effects there. The majority of this waste (80%) comes from land-based activity, although marine transportation significantly contributes as well. [ 72 ] It is a combination of chemicals and trash, most of which comes from land sources and is washed or blown into the ocean. This pollution results in damage to the environment , to the health of all organisms, and to economic structures worldwide. [ 73 ] Since most inputs come from land, via rivers , sewage , or the atmosphere , it means that continental shelves are more vulnerable to pollution. Air pollution is also a contributing factor, as it carries iron, carbonic acid, nitrogen , silicon, sulfur, pesticides , and dust particles into the ocean. [ 74 ] The pollution often comes from nonpoint sources such as agricultural runoff , wind-blown debris , and dust. These nonpoint sources are largely due to runoff that enters the ocean through rivers, but wind-blown debris and dust can also play a role, as these pollutants can settle into waterways and oceans. [ 75 ] Pathways of pollution include direct discharge, land runoff, ship pollution , bilge pollution , dredging (which can create dredge plumes ), atmospheric pollution and, potentially, deep sea mining .
By integrating socioeconomic metrics with ecosystem management solutions, scientific findings can be utilized to benefit both the environment and economy of local regions. Management efforts must be practical and cost-effective. In 2000, the Department of Natural Resource Economics at the University of Rhode Island has created a method for measuring and understanding the human dimensions of LMEs and for taking into consideration both socioeconomic and environmental costs and benefits of managing Large Marine Ecosystems. [ 76 ] [ 77 ] [ 78 ]
International attention to address the threats of coasts has been captured in Sustainable Development Goal 14 "Life Below Water" which sets goals for international policy focused on preserving coastal ecosystems and supporting more sustainable economic practices for coastal communities. [ 79 ] [ 5 ] Furthermore, the United Nations has declared 2021-2030 the UN Decade on Ecosystem Restoration , but restoration of coastal ecosystems has received insufficient attention. [ 80 ] | https://en.wikipedia.org/wiki/Marine_ecosystem |
Marine engineering is the engineering of boats, ships, submarines, and any other marine vessel . Here it is also taken to include the engineering of other ocean systems and structures – referred to in certain academic and professional circles as "ocean engineering". After completing this degree one can join a ship as an officer in engine department and eventually rise to the rank of a chief engineer . This rank is one of the top ranks onboard and is equal to the rank of a ship's captain. Marine engineering is the highly preferred course to join merchant Navy as an officer as it provides ample opportunities in terms of both onboard and onshore jobs.
Marine engineering applies a number of engineering sciences, including mechanical engineering , electrical engineering , electronic engineering , and computer Engineering , to the development, design, operation and maintenance of watercraft propulsion and ocean systems. [ 1 ] It includes but is not limited to power and propulsion plants, machinery, piping, automation and control systems for marine vehicles of any kind, as well as coastal and offshore structures.
Archimedes is traditionally regarded as the first marine engineer, having developed a number of marine engineering systems in antiquity. Modern marine engineering dates back to the beginning of the Industrial Revolution (early 1700s).
In 1807, Robert Fulton successfully used a steam engine to propel a vessel through the water. Fulton's ship used the engine to power a small wooden paddle wheel as its marine propulsion system. The integration of a steam engine into a watercraft to create a marine steam engine was the start of the marine engineering profession. Only twelve years after Fulton's Clermont had her first voyage, the Savannah marked the first sea voyage from America to Europe. Around 50 years later the steam powered paddle wheels had a peak with the creation of the Great Eastern , which was as big as one of the cargo ships of today, 700 feet in length, weighing 22,000 tons. Paddle steamers would become the front runners of the steamship industry for the next thirty years till the next type of propulsion came around. [ 2 ]
There are several educational paths to becoming a marine engineer, all of which includes earning a university or college degree, such as a Bachelor of Engineering (B.Eng. or B.E.), Bachelor of Science (B.Sc. or B.S.), Bachelor of Technology (B.Tech.), Bachelor of Technology Management and Marine Engineering (B.TecMan & MarEng), or a Bachelor of Applied Science (B.A.Sc.) in Marine Engineering.
Depending on the country and jurisdiction, to be licensed as a Marine engineer, a Master's degree, such as a Master of Engineering (M.Eng.), Master of Science (M.Sc or M.S.), or Master of Applied Science (M.A.Sc.) may be required.
Some marine engineers join the profession laterally, entering from other disciplines, like Mechanical Engineering , Civil Engineering , Electrical Engineering , Geomatics Engineering and Environmental Engineering , or from science-based fields, such as Geology , Geophysics , Physics , Geomatics , Earth Science , and Mathematics . To qualify as a marine engineer, those changing professions are required to earn a graduate Marine Engineering degree, such as an M.Eng, M.S., M.Sc., or M.A.Sc., after graduating from a different quantitative undergraduate program.
The fundamental subjects of marine engineering study usually include:
In the engineering of seagoing vessels, naval architecture is concerned with the overall design of the ship and its propulsion through the water, while marine engineering ensures that the ship systems function as per the design. [ 3 ] Although they have distinctive disciplines, naval architects and marine engineers often work side-by-side.
Ocean engineering is concerned with other structures and systems in or adjacent to the ocean, including offshore platforms , coastal structures such as piers and harbors , and other ocean systems such as ocean wave energy conversion and underwater life-support systems . [ 4 ] This in fact makes ocean engineering a distinctive field from marine engineering, which is concerned with the design and application of shipboard systems specifically. [ 5 ] However, on account of its similar nomenclature and multiple overlapping core disciplines (e.g. hydrodynamics , hydromechanics , and materials science ), "ocean engineering" sometimes operates under the umbrella term of "marine engineering", especially in industry and academia outside of the U.S. The same combination has been applied to the rest of this article.
Oceanography is a scientific field concerned with the acquisition and analysis of data to characterize the ocean. Although separate disciplines, marine engineering and oceanography are closely intertwined: marine engineers often use data gathered by oceanographers to inform their design and research, and oceanographers use tools designed by marine engineers (more specifically, oceanographic engineers) to advance their understanding and exploration of the ocean. [ 6 ]
Marine engineering incorporates many aspects of mechanical engineering. One manifestation of this relationship lies in the design of shipboard propulsion systems. Mechanical engineers design the main propulsion plant, the powering and mechanization aspects of the ship functions such as steering, anchoring , cargo handling, heating, ventilation, air conditioning interior and exterior communication, and other related requirements. Electrical power generation and electrical power distribution systems are typically designed by their suppliers; the only design responsibility of the marine engineering is installation.
Furthermore, an understanding of mechanical engineering topics such as fluid dynamics , fluid mechanics , linear wave theory , strength of materials , structural mechanics , and structural dynamics is essential to a marine engineer's repertoire of skills. These and other mechanical engineering subjects serve as an integral component of the marine engineering curriculum. [ 7 ]
Civil engineering concepts play in an important role in many marine engineering projects such as the design and construction of ocean structures, ocean bridges and tunnels , and port/harbor design.
Marine engineering often deals in the fields of electrical engineering and robotics , especially in applications related to employing deep-sea cables and UUVs.
A series of transoceanic fiber optic cables are responsible for connecting much of the world's communication via the internet , carrying as much as 99 percent of total global internet and signal traffic. These cables must be engineered to withstand deep-sea environments that are remote and often unforgiving, with extreme pressures and temperatures as well as potential interference by fishing , trawling , and sea life .
The use of unmanned underwater vehicles (UUVs) stands to benefit from the use of autonomous algorithms and networking. Marine engineers aim to learn how advancements in autonomy and networking can be used to enhance existing UUV technologies and facilitate the development of more capable underwater vehicles.
A knowledge of marine engineering proves useful in the field of petroleum engineering, as hydrodynamics and seabed integration serve as key elements in the design and maintenance of offshore oil platforms .
Marine construction is the process of building structures in or adjacent to large bodies of water, usually the sea. These structures can be built for a variety of purposes, including transportation, energy production, and recreation. Marine construction can involve the use of a variety of building materials, predominantly steel and concrete . Some examples of marine structures include ships, offshore platforms, moorings, pipelines, cables, wharves, bridges, tunnels, breakwaters and docks.
In the same way that civil engineers design to accommodate wind loads on building and bridges, marine engineers design to accommodate a ship or submarine struck by waves millions of times over the course of the vessel's life. These load conditions are also found in marine construction and coastal engineering
Any seagoing vessel has the constant need for hydrostatic stability. A naval architect , like an airplane designer, is concerned with stability . What makes the naval architect's job unique is that a ship operates in two fluids simultaneously: water and air. Even after a ship has been designed and put to sea, marine engineers face the challenge of balancing cargo, as stacking containers vertically increases the mass of the ship and shifts the center of gravity higher. The weight of fuel also presents a problem, as the pitch of the ship may cause the liquid to shift, resulting in an imbalance. In some vessels, this offset will be counteracted by storing water inside larger ballast tanks. Marine engineers are responsible for the task of balancing and tracking the fuel and ballast water of a ship. Floating offshore structures have similar constraints.
The saltwater environment faced by seagoing vessels makes them highly susceptible to corrosion. In every project, marine engineers are concerned with surface protection and preventing galvanic corrosion . Corrosion can be inhibited through cathodic protection by introducing pieces of metal (e.g. zinc ) to serve as a "sacrificial anode" in the corrosion reaction. This causes the metal to corrode instead of the ship's hull. Another way to prevent corrosion is by sending a controlled amount of low DC current through the ship's hull, thereby changing the hull's electrical charge and delaying the onset of electro-chemical corrosion. Similar problems are encountered in coastal and offshore structures.
Anti-fouling is the process of eliminating obstructive organisms from essential components of seawater systems. Depending on the nature and location of marine growth, this process is performed in a number of different ways:
The burning of marine fuels releases harmful pollutants into the atmosphere. Ships burn marine diesel in addition to heavy fuel oil . Heavy fuel oil, being the heaviest of refined oils , releases sulfur dioxide when burned. Sulfur dioxide emissions have the potential to raise atmospheric and ocean acidity causing harm to marine life. However, heavy fuel oil may only be burned in international waters due to the pollution created. It is commercially advantageous due to the cost effectiveness compared to other marine fuels. It is prospected that heavy fuel oil will be phased out of commercial use by the year 2020 (Smith, 2018). [ 10 ]
Water, oil, and other substances collect at the bottom of the ship in what is known as the bilge. Bilge water is pumped overboard, but must pass a pollution threshold test of 15 ppm (parts per million) of oil to be discharged. Water is tested and either discharged if clean or recirculated to a holding tank to be separated before being tested again. The tank it is sent back to, the oily water separator, utilizes gravity to separate the fluids due to their viscosity. Ships over 400 gross tons are required to carry the equipment to separate oil from bilge water. Further, as enforced by MARPOL, all ships over 400 gross tons and all oil tankers over 150 gross tons are required to log all oil transfers in an oil record book (EPA, 2011). [ 11 ]
Cavitation is the process of forming an air bubble in a liquid due to the vaporization of that liquid cause by an area of low pressure. This area of low pressure lowers the boiling point of a liquid allowing it to vaporize into a gas. Cavitation can take place in pumps, which can cause damage to the impeller that moves the fluids through the system. Cavitation is also seen in propulsion. Low pressure pockets form on the surface of the propeller blades as its revolutions per minute increase (IIMS, 2015). [ 12 ] Cavitation on the propeller causes a small but violent implosion which could warp the propeller blade. To remedy the issue, more blades allow the same amount of propulsion force but at a lower rate of revolutions. This is crucial for submarines as the propeller needs to keep the vessel relatively quiet to stay hidden. With more propeller blades, the vessel is able to achieve the same amount of propulsion force at lower shaft revolutions.
The following categories provide a number of focus areas in which marine engineers direct their efforts.
In designing systems that operate in the arctic (especially scientific equipment such as meteorological instrumentation and oceanographic buoys ), marine engineers must overcome an array of design challenges. Equipment must be able to operate at extreme temperatures for prolonged periods of time, often with little to no maintenance. This creates the need for exceptionally temperature-resistant materials and durable precision electronic components. [ citation needed ]
Coastal engineering applies a mixture of civil engineering and other disciplines to create coastal solutions for areas along or near the ocean. In protecting coastlines from wave forces, erosion , and sea level rise , marine engineers must consider whether they will use a "gray" infrastructure solution - such as a breakwater, culvert, or sea wall made from rocks and concrete - or a "green" infrastructure solution that incorporates aquatic plants, mangroves, and/or marsh ecosystems. [ 13 ] It has been found that gray infrastructure costs more to build and maintain, but it may provide better protection against ocean forces in high-energy wave environments. [ 14 ] A green solution is generally less expensive and more well-integrated with local vegetation, but may be susceptible to erosion or damage if executed improperly. [ 15 ] In many cases engineers will select a hybrid approach that combines elements of both gray and green solutions. [ 16 ]
The design of underwater life-support systems such as underwater habitats presents a unique set of challenges requiring a detailed knowledge of pressure vessels, diving physiology , and thermodynamics.
Marine engineers may design or make frequent use of unmanned underwater vehicles , which operate underwater without a human aboard. UUVs often perform work in locations which would be otherwise impossible or difficult to access by humans due to a number of environmental factors (e.g. depth, remoteness, and/or temperature). UUVs can be remotely operated by humans, like in the case of remotely operated vehicles , semi-autonomous , or autonomous .
The development of oceanographic sciences , subsea engineering and the ability to detect, track and destroy submarines ( anti-submarine warfare ) required the parallel development of a host of marine scientific instrumentation and sensors . Visible light is not transferred far underwater, so the medium for transmission of data is primarily acoustic . High-frequency sound is used to measure the depth of the ocean, determine the nature of the seafloor, and detect submerged objects. The higher the frequency, the higher the definition of the data that is returned. Sound Navigation and Ranging or SONAR was developed during the First World War to detect submarines , and has been greatly refined through to the present day. Submarines similarly use sonar equipment to detect and target other submarines and surface ships, and to detect submerged obstacles such as seamounts that pose a navigational obstacle. Simple echo-sounders point straight down and can give an accurate reading of ocean depth (or look up at the underside of sea-ice).
More advanced echo sounders use a fan-shaped beam or sound, or multiple beams to derive highly detailed images of the ocean floor. High power systems can penetrate the soil and seabed rocks to give information about the geology of the seafloor, and are widely used in geophysics for the discovery of hydrocarbons , or for engineering survey.
For close-range underwater communications, optical transmission is possible, mainly using blue lasers . These have a high bandwidth compared with acoustic systems, but the range is usually only a few tens of metres, and ideally at night.
As well as acoustic communications and navigation, sensors have been developed to measure ocean parameters such as temperature, salinity , oxygen levels and other properties including nitrate levels, levels of trace chemicals and environmental DNA . The industry trend has been towards smaller, more accurate and more affordable systems so that they can be purchased and used by university departments and small companies as well as large corporations, research organisations and governments. The sensors and instruments are fitted to autonomous and remotely-operated systems as well as ships, and are enabling these systems to take on tasks that hitherto required an expensive human-crewed platform.
Manufacture of marine sensors and instruments mainly takes place in Asia, Europe and North America. Products are advertised in specialist journals, and through Trade Shows such as Oceanology International and Ocean Business which help raise awareness of the products.
In every coastal and offshore project, environmental sustainability is an important consideration for the preservation of ocean ecosystems and natural resources . Instances in which marine engineers benefit from knowledge of environmental engineering include creation of fisheries , clean-up of oil spills , and creation of coastal solutions . [ 17 ]
A number of systems designed fully or in part by marine engineers are used offshore - far away from coastlines.
The design of offshore oil platforms involves a number of marine engineering challenges. Platforms must be able to withstand ocean currents , wave forces, and saltwater corrosion while remaining structurally integral and fully anchored into the seabed . Additionally, drilling components must be engineered to handle these same challenges with a high factor of safety to prevent oil leaks and spills from contaminating the ocean.
Offshore wind farms encounter many similar marine engineering challenges to oil platforms. They provide a source of renewable energy with a higher yield than wind farms on land, while encountering less resistance from the general public ( see NIMBY ). [ 18 ]
Marine engineers continue to investigate the possibility of ocean wave energy as a viable source of power for distributed or grid applications. Many designs have been proposed and numerous prototypes have been built, but the problem of harnessing wave energy in a cost-effective manner remains largely unresolved. [ 19 ]
A marine engineer may also deal with the planning, creation, expansion, and modification of port and harbor designs. Harbors can be natural or artificial and protect anchored ships from wind, waves, and currents. [ 20 ] Ports can be defined as a city, town, or place where ships are moored, loaded, or unloaded. Ports typically reside within a harbor and are made up of one or more individual terminals that handle a particular cargo including passengers, bulk cargo , or containerized cargo . [ 21 ] Marine engineers plan and design various types of marine terminals and structures found in ports, and they must understand the loads imposed on these structures over the course of their lifetime.
Marine salvage techniques are continuously modified and improved to recover shipwrecks. Marine engineers use their skills to assist at some stages of this process.
With a diverse engineering background, marine engineers work in a variety of industry jobs across every field of math, science, technology, and engineering. A few companies such as Oceaneering International and Van Oord specialize in marine engineering, while other companies consult marine engineers for specific projects. Such consulting commonly occurs in the oil industry, with companies such as ExxonMobil and BP hiring marine engineers to manage aspects of their offshore drilling projects.
Marine engineering lends itself to a number of military applications – mostly related to the Navy . The United States Navy 's Seabees , Civil Engineer Corps , and Engineering Duty Officers often perform work related to marine engineering. Military contractors (especially those in naval shipyards) and the Army Corps of Engineers play a role in certain marine engineering projects as well.
In 2012, the average annual earnings for marine engineers in the U.S. were $96,140 with average hourly earnings of $46.22. [ 22 ] As a field, marine engineering is predicted to grow approximately 12% from 2016 to 2026. Currently, there are about 8,200 naval architects and marine engineers employed, however, this number is expected to increase to 9,200 by 2026 (BLS, 2017). [ 23 ] This is due at least in part to the critical role of the shipping industry on the global market supply chain; 80% of the world's trade by volume is done overseas by close to 50,000 ships, all of which require marine engineers aboard and shoreside (ICS, 2017). [ 24 ] Additionally, offshore energy continues to grow, and a greater need exists for coastal solutions due to sea level rise .
Maritime universities are dedicated to teaching and training students in maritime professions. Marine engineers generally have a bachelor's degree in marine engineering, marine engineering technology, or marine systems engineering. Practical training is valued by employers alongside the bachelor's degree.
A number of institutions - including MIT , [ 26 ] UC Berkeley , [ 27 ] the U.S. Naval Academy , [ 28 ] and Texas A&M University [ 29 ] - offer a four-year Bachelor of Science degree specifically in ocean engineering. Accredited programs consist of basic undergraduate math and science subjects such as calculus , statistics , chemistry , and physics ; fundamental engineering subjects such as statics , dynamics , electrical engineering , and thermodynamics ; and more specialized subjects such as ocean structural analysis , hydromechanics , and coastal management .
Graduate students in ocean engineering take classes on more advanced, in-depth subjects while conducting research to complete a graduate-level thesis. The Massachusetts Institute of Technology offers master's and PhD degrees specifically in ocean engineering. [ 30 ] Additionally, MIT co-hosts a joint program with the Woods Hole Oceanographic Institution for students studying ocean engineering and other ocean-related topics at the graduate level. [ 31 ] [ 32 ]
Journals about ocean engineering include Ocean Engineering , [ 33 ] the IEEE Journal of Oceanic Engineering [ 34 ] and the Journal of Waterway, Port, Coastal, and Ocean Engineering . [ 35 ]
Conferences in the field of marine engineering include the IEEE Oceanic Engineering Society's OCEANS Conference and Exposition [ 36 ] and the European Wave and Tidal Energy Conference (EWTEC). [ 37 ] | https://en.wikipedia.org/wiki/Marine_engineering |
A marine habitat is a habitat that supports marine life . Marine life depends in some way on the saltwater that is in the sea (the term marine comes from the Latin mare , meaning sea or ocean). A habitat is an ecological or environmental area inhabited by one or more living species . [ 1 ] The marine environment supports many kinds of these habitats.
Marine habitats can be divided into coastal and open ocean habitats. Coastal habitats are found in the area that extends from as far as the tide comes in on the shoreline out to the edge of the continental shelf . Most marine life is found in coastal habitats, even though the shelf area occupies only seven percent of the total ocean area. Open ocean habitats are found in the deep ocean beyond the edge of the continental shelf.
Alternatively, marine habitats can be divided into pelagic and demersal zones . Pelagic habitats are found near the surface or in the open water column , away from the bottom of the ocean. Demersal habitats are near or on the bottom of the ocean. An organism living in a pelagic habitat is said to be a pelagic organism, as in pelagic fish . Similarly, an organism living in a demersal habitat is said to be a demersal organism, as in demersal fish . Pelagic habitats are intrinsically shifting and ephemeral, depending on what ocean currents are doing.
Marine habitats can be modified by their inhabitants. Some marine organisms, like corals , kelp , mangroves and seagrasses , are ecosystem engineers which reshape the marine environment to the point where they create further habitat for other organisms. By volume the ocean provides most of the habitable space on the planet. [ 2 ]
In contrast to terrestrial habitats, marine habitats are shifting and ephemeral . Swimming organisms find areas by the edge of a continental shelf a good habitat, but only while upwellings bring nutrient rich water to the surface. Shellfish find habitat on sandy beaches, but storms, tides and currents mean their habitat continually reinvents itself.
The presence of seawater is common to all marine habitats. Beyond that many other things determine whether a marine area makes a good habitat and the type of habitat it makes. For example:
There are five major oceans, of which the Pacific Ocean is nearly as large as the rest put together. Coastlines fringe the land for nearly 380,000 kilometres.
Altogether, the ocean occupies 71 percent of the world surface, averaging nearly four kilometres in depth. By volume, the ocean contains more than 99 percent of the Earth's liquid water. [ 10 ] [ 11 ] [ 12 ] The science fiction writer Arthur C. Clarke has pointed out it would be more appropriate to refer to the planet Earth as the planet Sea or the planet
Ocean. [ 13 ] [ 14 ]
Marine habitats can be broadly divided into pelagic and demersal habitats. Pelagic habitats are the habitats of the open water column , away from the bottom of the ocean. Demersal habitats are the habitats that are near or on the bottom of the ocean. An organism living in a pelagic habitat is said to be a pelagic organism, as in pelagic fish . Similarly, an organism living in a demersal habitat is said to be a demersal organism, as in demersal fish . Pelagic habitats are intrinsically ephemeral, depending on what ocean currents are doing.
The land-based ecosystem depends on topsoil and fresh water, while the marine ecosystem depends on dissolved nutrients washed down from the land. [ 15 ]
Ocean deoxygenation poses a threat to marine habitats, due to the growth of low oxygen zones. [ 16 ]
In marine systems, ocean currents have a key role determining which areas are effective as habitats, since ocean currents transport the basic nutrients needed to support marine life. [ 17 ] Plankton are the life forms that inhabit the ocean that are so small (less than 2 mm) that they cannot effectively propel themselves through the water, but must drift instead with the currents. If the current carries the right nutrients, and if it also flows at a suitably shallow depth where there is plenty of sunlight, then such a current itself can become a suitable habitat for photosynthesizing tiny algae called phytoplankton . These tiny plants are the primary producers in the ocean, at the start of the food chain . In turn, as the population of drifting phytoplankton grows, the water becomes a suitable habitat for zooplankton , which feed on the phytoplankton. While phytoplankton are tiny drifting plants, zooplankton are tiny drifting animals, such as the larvae of fish and marine invertebrates . If sufficient zooplankton establish themselves, the current becomes a candidate habitat for the forage fish that feed on them. And then if sufficient forage fish move to the area, it becomes a candidate habitat for larger predatory fish and other marine animals that feed on the forage fish. In this dynamic way, the current itself can, over time, become a moving habitat for multiple types of marine life.
Ocean currents can be generated by differences in the density of the water. How dense water is depends on how saline or warm it is. If water contains differences in salt content or temperature, then the different densities will initiate a current. Water that is saltier or cooler will be denser, and will sink in relation to the surrounding water. Conversely, warmer and less salty water will float to the surface. Atmospheric winds and pressure differences also produces surface currents, waves and seiches . Ocean currents are also generated by the gravitational pull of the sun and moon ( tides ), and seismic activity ( tsunami ). [ 17 ]
The rotation of the Earth affects the direction ocean currents take, and explains which way the large circular ocean gyres rotate in the image above left. Suppose a current at the equator is heading north. The Earth rotates eastward, so the water possesses that rotational momentum. But the further the water moves north, the slower the earth moves eastward. If the current could get to the North Pole, the earth would not be moving eastward at all. To conserve its rotational momentum, the further the current travels north the faster it must move eastward. So the effect is that the current curves to the right. This is the Coriolis effect . It is weakest at the equator and strongest at the poles. The effect is opposite south of the equator, where currents curve left. [ 17 ]
Seabed topography (ocean topography or marine topography) refers to the shape of the land ( topography ) when it interfaces with the ocean. These shapes are obvious along coastlines, but they occur also in significant ways underwater. The effectiveness of marine habitats is partially defined by these shapes, including the way they interact with and shape ocean currents , and the way sunlight diminishes when these landforms occupy increasing depths. Tidal networks depend on the balance between sedimentary processes and hydrodynamics however, anthropogenic influences can impact the natural system more than any physical driver. [ 18 ]
Marine topographies include coastal and oceanic landforms ranging from coastal estuaries and shorelines to continental shelves and coral reefs . Further out in the open ocean, they include underwater and deep sea features such as ocean rises and seamounts . The submerged surface has mountainous features, including a globe-spanning mid-ocean ridge system, as well as undersea volcanoes , [ 19 ] oceanic trenches , submarine canyons , oceanic plateaus and abyssal plains .
One measure of the relative importance of different marine habitats is the rate at which they produce biomass .
Marine coasts are dynamic environments which constantly change, like the ocean which partially shape them. The Earth's natural processes, including weather and sea level change , result in the erosion , accretion and resculpturing of coasts as well as the flooding and creation of continental shelves and drowned river valleys .
The main agents responsible for deposition and erosion along coastlines are waves , tides and currents . The formation of coasts also depends on the nature of the rocks they are made of – the harder the rocks the less likely they are to erode, so variations in rock hardness result in coastlines with different shapes.
Tides often determine the range over which sediment is deposited or eroded. Areas with high tidal ranges allow waves to reach farther up the shore, and areas with lower tidal ranges produce deposition at a smaller elevation interval. The tidal range is influenced by the size and shape of the coastline. Tides do not typically cause erosion by themselves; however, tidal bores can erode as the waves surge up river estuaries from the ocean. [ 24 ]
Waves erode coastline as they break on shore releasing their energy; the larger the wave the more energy it releases and the more sediment it moves. Sediment deposited by waves comes from eroded cliff faces and is moved along the coastline by the waves. Sediment deposited by rivers is the dominant influence on the amount of sediment located on a coastline. [ 26 ]
The sedimentologist Francis Shepard classified coasts as primary or secondary . [ 27 ]
Continental coastlines usually have a continental shelf , a shelf of relatively shallow water, less than 200 metres deep, which extends 68 km on average beyond the coast. Worldwide, continental shelves occupy a total area of about 24 million km 2 (9 million sq mi), 8% of the ocean's total area and nearly 5% of the world's total area. [ 29 ] [ 30 ] Since the continental shelf is usually less than 200 metres deep, it follows that coastal habitats are generally photic , situated in the sunlit epipelagic zone . This means the conditions for photosynthetic processes so important for primary production , are available to coastal marine habitats. Because land is nearby, there are large discharges of nutrient rich land runoff into coastal waters. Further, periodic upwellings from the deep ocean can provide cool and nutrient rich currents along the edge of the continental shelf.
As a result, coastal marine life is the most abundant in the world. It is found in tidal pools , fjords and estuaries , near sandy shores and rocky coastlines, around coral reefs and on or above the continental shelf. Coastal fish include small forage fish as well as the larger predator fish that feed on them. Forage fish thrive in inshore waters where high productivity results from upwelling and shoreline run off of nutrients. Some are partial residents that spawn in streams, estuaries and bays, but most complete their life cycle in the zone. [ 31 ] There can also be a mutualism between species that occupy adjacent marine habitats. For example, fringing reefs just below low tide level have a mutually beneficial relationship with mangrove forests at high tide level and sea grass meadows in between: the reefs protect the mangroves and seagrass from strong currents and waves that would damage them or erode the sediments in which they are rooted, while the mangroves and seagrass protect the coral from large influxes of silt , fresh water and pollutants . This additional level of variety in the environment is beneficial to many types of coral reef animals, which for example may feed in the sea grass and use the reefs for protection or breeding. [ 32 ]
Coastal habitats are the most visible marine habitats, but they are not the only important marine habitats. Coastlines run for 380,000 kilometres, and the total volume of the ocean is 1,370 million cu km. This means that for each metre of coast, there is 3.6 cu km of ocean space available somewhere for marine habitats.
Intertidal zones , those areas close to shore, are constantly being exposed and covered by the ocean's tides . A huge array of life lives within this zone.
Shore habitats range from the upper intertidal zones to the area where land vegetation takes prominence. It can be underwater anywhere from daily to very infrequently. Many species here are scavengers, living off of sea life that is washed up on the shore. Many land animals also make much use of the shore and intertidal habitats. A subgroup of organisms in this habitat bores and grinds exposed rock through the process of bioerosion .
Sandy shores, also called beaches , are coastal shorelines where sand accumulates. Waves and currents shift the sand, continually building and eroding the shoreline. Longshore currents flow parallel to the beaches, making waves break obliquely on the sand. These currents transport large amounts of sand along coasts, forming spits , barrier islands and tombolos . Longshore currents also commonly create offshore bars , which give beaches some stability by reducing erosion. [ 33 ]
Sandy shores are full of life. The grains of sand host diatoms , bacteria and other microscopic creatures. Some fish and turtles return to certain beaches and spawn eggs in the sand. Birds habitat beaches, like gulls , loons , sandpipers , terns and pelicans . Aquatic mammals , such sea lions, recuperate on them. Clams , periwinkles , crabs , shrimp , starfish and sea urchins are found on most beaches. [ 34 ]
Sand is a sediment made from small grains or particles with diameters between about 60 μm and 2 mm. [ 35 ] Mud (see mudflats below) is a sediment made from particles finer than sand. This small particle size means that mud particles tend to stick together, whereas sand particles do not. Mud is not easily shifted by waves and currents, and when it dries out, cakes into a solid. By contrast, sand is easily shifted by waves and currents, and when sand dries out it can be blown in the wind, accumulating into shifting sand dunes . Beyond the high tide mark, if the beach is low-lying, the wind can form rolling hills of sand dunes. Small dunes shift and reshape under the influence of the wind while larger dunes stabilise the sand with vegetation. [ 33 ]
Ocean processes grade loose sediments to particle sizes other than sand, such as gravel or cobbles . Waves breaking on a beach can leave a berm , which is a raised ridge of coarser pebbles or sand, at the high tide mark. Shingle beaches are made of particles larger than sand, such as cobbles, or small stones. These beaches make poor habitats. Little life survives because the stones are churned and pounded together by waves and currents. [ 33 ]
The relative solidity of rocky shores seems to give them a permanence compared to the shifting nature of sandy shores. This apparent stability is not real over even quite short geological time scales, but it is real enough over the short life of an organism. In contrast to sandy shores, plants and animals can anchor themselves to the rocks. [ 36 ]
Competition can develop for the rocky spaces. For example, barnacles can compete successfully on open intertidal rock faces to the point where the rock surface is covered with them. Barnacles resist desiccation and grip well to exposed rock faces. However, in the crevices of the same rocks, the inhabitants are different. Here mussels can be the successful species, secured to the rock with their byssal threads . [ 36 ]
Rocky and sandy coasts are vulnerable because humans find them attractive and want to live near them. An increasing proportion of the humans live by the coast, putting pressure on coastal habitats. [ 36 ]
Mudflats are coastal wetlands that form when mud is deposited by tides or rivers. They are found in sheltered areas such as bays , bayous , lagoons , and estuaries . Mudflats may be viewed geologically as exposed layers of bay mud , resulting from deposition of estuarine silts , clays and marine animal detritus . Most of the sediment within a mudflat is within the intertidal zone , and thus the flat is submerged and exposed approximately twice daily.
Mangrove swamps and salt marshes form important coastal habitats in tropical and temperate areas respectively.
Mangroves are species of shrubs and medium size trees that grow in saline coastal sediment habitats in the tropics and subtropics – mainly between latitudes 25° N and 25° S. The saline conditions tolerated by various species range from brackish water , through pure seawater (30 to 40 ppt ), to water concentrated by evaporation to over twice the salinity of ocean seawater (up to 90 ppt). [ 37 ] [ 38 ] There are many mangrove species, not all closely related. The term "mangrove" is used generally to cover all of these species, and it can be used narrowly to cover just mangrove trees of the genus Rhizophora .
Mangroves form a distinct characteristic saline woodland or shrubland habitat, called a mangrove swamp or mangrove forest . [ 39 ] Mangrove swamps are found in depositional coastal environments, where fine sediments (often with high organic content) collect in areas protected from high-energy wave action. Mangroves dominate three quarters of tropical coastlines. [ 38 ]
An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea . [ 40 ] Estuaries form a transition zone between river environments and ocean environments and are subject to both marine influences, such as tides, waves, and the influx of saline water; and riverine influences, such as flows of fresh water and sediment. The inflow of both seawater and freshwater provide high levels of nutrients in both the water column and sediment, making estuaries among the most productive natural habitats in the world. [ 41 ]
Most estuaries were formed by the flooding of river-eroded or glacially scoured valleys when sea level began to rise about 10,000-12,000 years ago. [ 42 ] They are amongst the most heavily populated areas throughout the world, with about 60% of the world's population living along estuaries and the coast. As a result, estuaries are suffering degradation by many factors, including sedimentation from soil erosion from deforestation; overgrazing and other poor farming practices; overfishing; drainage and filling of wetlands; eutrophication due to excessive nutrients from sewage and animal wastes; pollutants including heavy metals, PCBs, radionuclides and hydrocarbons from sewage inputs; and diking or damming for flood control or water diversion. [ 42 ]
Estuaries provide habitats for a large number of organisms and support very high productivity. Estuaries provide habitats for salmon and sea trout nurseries, [ 43 ] as well as migratory bird populations. [ 44 ] Two of the main characteristics of estuarine life are the variability in salinity and sedimentation . Many species of fish and invertebrates have various methods to control or conform to the shifts in salt concentrations and are termed osmoconformers and osmoregulators . Many animals also burrow to avoid predation and to live in the more stable sedimental environment. However, large numbers of bacteria are found within the sediment which have a very high oxygen demand. This reduces the levels of oxygen within the sediment often resulting in partially anoxic conditions, which can be further exacerbated by limited water flux. Phytoplankton are key primary producers in estuaries. They move with the water bodies and can be flushed in and out with the tides . Their productivity is largely dependent on the turbidity of the water. The main phytoplankton present are diatoms and dinoflagellates which are abundant in the sediment.
Kelp forests are underwater areas with a high density of kelp . They form some of the most productive and dynamic ecosystems on Earth. [ 45 ] Smaller areas of anchored kelp are called kelp beds . Kelp forests occur worldwide throughout temperate and polar coastal oceans. [ 45 ]
Kelp forests provide a unique three-dimensional habitat for marine organisms and are a source for understanding many ecological processes. Over the last century, they have been the focus of extensive research, particularly in trophic ecology, and continue to provoke important ideas that are relevant beyond this unique ecosystem. For example, kelp forests can influence coastal oceanographic patterns [ 46 ] and provide many ecosystem services . [ 47 ]
However, humans have contributed to kelp forest degradation . Of particular concern are the effects of overfishing nearshore ecosystems, which can release herbivores from their normal population regulation and result in the over-grazing of kelp and other algae. [ 48 ] This can rapidly result in transitions to barren landscapes where relatively few species persist. [ 49 ]
Frequently considered an ecosystem engineer , kelp provides a physical substrate and habitat for kelp forest communities. [ 50 ] In algae (Kingdom: Protista ), the body of an individual organism is known as a thallus rather than as a plant (Kingdom: Plantae ). The morphological structure of a kelp thallus is defined by three basic structural units: [ 49 ]
In addition, many kelp species have pneumatocysts , or gas-filled bladders, usually located at the base of fronds near the stipe. These structures provide the necessary buoyancy for kelp to maintain an upright position in the water column.
The environmental factors necessary for kelp to survive include hard substrate (usually rock), high nutrients (e.g., nitrogen, phosphorus), and light (minimum annual irradiance dose > 50 E m −2 [ 51 ] ). Especially productive kelp forests tend to be associated with areas of significant oceanographic upwelling , a process that delivers cool nutrient-rich water from depth to the ocean's mixed surface layer . [ 51 ] Water flow and turbulence facilitate nutrient assimilation across kelp fronds throughout the water column. [ 52 ] Water clarity affects the depth to which sufficient light can be transmitted. In ideal conditions, giant kelp ( Macrocystis spp. ) can grow as much as 30-60 centimetres vertically per day. Some species such as Nereocystis are annual while others like Eisenia are perennial , living for more than 20 years. [ 53 ] In perennial kelp forests, maximum growth rates occur during upwelling months (typically spring and summer) and die-backs correspond to reduced nutrient availability, shorter photoperiods and increased storm frequency. [ 49 ]
Seagrasses are flowering plants from one of four plant families which grow in marine environments. They are called seagrasses because the leaves are long and narrow and are very often green, and because the plants often grow in large meadows which look like grassland. Since seagrasses photosynthesize and are submerged, they must grow submerged in the photic zone , where there is enough sunlight. For this reason, most occur in shallow and sheltered coastal waters anchored in sand or mud bottoms.
Seagrasses form extensive beds or meadows , which can be either monospecific (made up of one species) or multispecific (where more than one species co-exist). Seagrass beds make highly diverse and productive ecosystems . They are home to phyla such as juvenile and adult fish, epiphytic and free-living macroalgae and microalgae , mollusks , bristle worms , and nematodes . Few species were originally considered to feed directly on seagrass leaves (partly because of their low nutritional content), but scientific reviews and improved working methods have shown that seagrass herbivory is a highly important link in the food chain, with hundreds of species feeding on seagrasses worldwide, including green turtles , dugongs , manatees , fish , geese , swans , sea urchins and crabs .
Seagrasses are ecosystem engineers in the sense that they partly create their own habitat. The leaves slow down water-currents increasing sedimentation , and the seagrass roots and rhizomes stabilize the seabed. Their importance to associated species is mainly due to provision of shelter (through their three-dimensional structure in the water column), and due to their extraordinarily high rate of primary production . As a result, seagrasses provide coastal zones with ecosystem services , such as fishing grounds , wave protection, oxygen production and protection against coastal erosion . Seagrass meadows account for 15% of the ocean's total carbon storage. [ 54 ]
A reef is a ridge or shoal of rock, coral or similar relatively stable material, lying beneath the surface of a natural body of water. [ 55 ] Many reefs result from natural, abiotic processes but there are also reefs such as the coral reefs of tropical waters formed by biotic processes dominated by corals and coralline algae . Artificial reefs such as shipwrecks and other anthropogenic underwater structures may occur intentionally or as the result of an accident, and sometimes have a designed role in enhancing the physical complexity of featureless sand bottoms, thereby attracting a more diverse assemblage of organisms. Reefs are often quite near to the surface, but not all definitions require this. [ 55 ] Fringing reefs, the most common type of reef, are found close to shorelines and surrounding islands. [ 56 ]
Rocky reefs are underwater outcrops of rock projecting above the adjacent unconsolidated surface with varying relief. They can be found in depth ranges from intertidal to deep water and provide a substrate for a large range of sessile benthic organisms, and shelter for a large range of mobile organisms. [ 57 ]
Coral reefs comprise some of the densest and most diverse habitats in the world. The best-known types of reefs are tropical coral reefs which exist in most tropical waters; however, coral reefs can also exist in cold water. Reefs are built up by corals and other calcium -depositing animals, usually on top of a rocky outcrop on the ocean floor. Reefs can also grow on other surfaces, which has made it possible to create artificial reefs . Coral reefs also support a huge community of life, including the corals themselves, their symbiotic zooxanthellae , tropical fish and many other organisms.
Much attention in marine biology is focused on coral reefs and the El Niño weather phenomenon. In 1998, coral reefs experienced the most severe mass bleaching events on record, when vast expanses of reefs across the world died because sea surface temperatures rose well above normal. [ 58 ] [ 59 ] Some reefs are recovering, but scientists say that between 50% and 70% of the world's coral reefs are now endangered and predict that global warming could exacerbate this trend. [ 60 ] [ 61 ] [ 62 ] [ 63 ]
The surface microlayer of the ocean serves as the transitional area between the atmosphere and the ocean. It covers around 70% of the Earth's surface as it covers most of the ocean waters on the planet. [ 65 ] The microlayer is known for its unique biological and chemical properties which give it a small ecosystem of its own and serves as a distinct habitat from the deeper ocean waters.
The surface microlayer is not in fact entirely aqueous like the rest of the ocean, but is closer to a kind of hydrated gel composed of concentrated nutrients forming a biological film over the water it covers. This film is rich in microbes which mediate the interactions between the sun, the atmosphere, and the waters below.
Although thin, the surface microlayer is critical for life beneath it. Because of the environment rich in microbes and nutrients, larvae of fish and other aquatic animals are often laid in the microlayer to incubate. The plankton in the microlayer are distinctly adapted to withstand high levels of radiation, and serve as buffers to prevent this potentially harmful radiation from reaching the deeper water. Environmental changes such as aerosols or dust storms can cause these surface plankton to become overproductive, leading to blooms . [ 65 ]
Because of the unique properties of the microlayer, pollutants often accumulate within and use it to reach other parts of the ocean. Hydrophobic compounds, such as petroleum , flame retardants, and heavy metals, have a particular affinity for the surface microlayer. Recently, the abundance of aerosols and microplastics has also had an impact on the SML and their accumulation has led to many problems, such as animal ingestion of these compounds leading to widespread disruption of balance and spread of these compounds among marine communities.
The surface microlayer is also critical to gas exchange between the atmosphere and the ocean. Because the microlayer is filled with microbes, it is widely theorized that it plays a critical role in gas exchange and uptake of nutrients, but relatively little data on this has been collected. The central feature of the microlayer is the temperature, as it is an indicator of how pollutants and human activity affects the ocean. [ 65 ]
The surface waters are sunlit. The waters down to about 200 metres are said to be in the epipelagic zone . Enough sunlight enters the epipelagic zone to allow photosynthesis by phytoplankton . The epipelagic zone is usually low in nutrients. This partially because the organic debris produced in the zone, such as excrement and dead animals, sink to the depths and are lost to the upper zone. Photosynthesis can happen only if both sunlight and nutrients are present. [ 64 ]
In some places, like at the edge of continental shelves, nutrients can upwell from the ocean depth, or land runoff can be distributed by storms and ocean currents. In these areas, given that both sunlight and nutrients are now present, phytoplankton can rapidly establish itself, multiplying so fast that the water turns green from the chlorophyll, resulting in an algal bloom . These nutrient rich surface waters are among the most biologically productive in the world, supporting billions of tonnes of biomass . [ 64 ]
"Phytoplankton are eaten by zooplankton - small animals which, like phytoplankton, drift in the ocean currents. The most abundant zooplankton species are copepods and krill : tiny crustaceans that are the most numerous animals on Earth. Other types of zooplankton include jelly fish and the larvae of fish, marine worms , starfish , and other marine organisms". [ 64 ] In turn, the zooplankton are eaten by filter-feeding animals, including some seabirds , small forage fish like herrings and sardines, whale sharks , manta rays , and the largest animal in the world, the blue whale . Yet again, moving up the foodchain , the small forage fish are in turn eaten by larger predators, such as tuna, marlin, sharks, large squid, seabirds, dolphins, and toothed whales . [ 64 ]
The open ocean is relatively unproductive because of a lack of nutrients, yet because it is so vast, it has more overall primary production than any other marine habitat. Only about 10 percent of marine species live in the open ocean. But among them are the largest and fastest of all marine animals, as well as the animals that dive the deepest and migrate the longest. In the depths lurk animal that, to our eyes, appear hugely alien. [ 66 ]
The deep sea starts at the aphotic zone , the point where sunlight loses most of its energy in the water. Many life forms that live at these depths have the ability to create their own light a unique evolution known as bio-luminescence . [ citation needed ]
In the deep ocean, the waters extend far below the epipelagic zone, and support very different types of pelagic life forms adapted to living in these deeper zones. [ 68 ]
Much of the aphotic zone 's energy is supplied by the open ocean in the form of detritus . In deep water, marine snow is a continuous shower of mostly organic detritus falling from the upper layers of the water column. Its origin lies in activities within the productive photic zone . Marine snow includes dead or dying plankton , protists ( diatoms ), fecal matter, sand, soot and other inorganic dust. The "snowflakes" grow over time and may reach several centimetres in diameter, travelling for weeks before reaching the ocean floor. However, most organic components of marine snow are consumed by microbes , zooplankton and other filter-feeding animals within the first 1,000 metres of their journey, that is, within the epipelagic zone. In this way marine snow may be considered the foundation of deep-sea mesopelagic and benthic ecosystems : As sunlight cannot reach them, deep-sea organisms rely heavily on marine snow as an energy source. [ 69 ]
Some deep-sea pelagic groups, such as the lanternfish , ridgehead , marine hatchetfish , and lightfish families are sometimes termed pseudoceanic because, rather than having an even distribution in open water, they occur in significantly higher abundances around structural oases, notably seamounts and over continental slopes . The phenomenon is explained by the likewise abundance of prey species which are also attracted to the structures. [ citation needed ]
The fish in the different pelagic and deep water benthic zones are physically structured, and behave in ways, that differ markedly from each other. Groups of coexisting species within each zone all seem to operate in similar ways, such as the small mesopelagic vertically migrating plankton-feeders, the bathypelagic anglerfishes , and the deep water benthic rattails . " [ 70 ]
Ray finned species, with spiny fins, are rare among deep sea fishes, which suggests that deep sea fish are ancient and so well adapted to their environment that invasions by more modern fishes have been unsuccessful. [ 71 ] The few ray fins that do exist are mainly in the Beryciformes and Lampriformes , which are also ancient forms. Most deep sea pelagic fishes belong to their own orders, suggesting a long evolution in deep sea environments. In contrast, deep water benthic species, are in orders that include many related shallow water fishes. [ 72 ]
The umbrella mouth gulper is a deep sea eel with an enormous loosely hinged mouth. It can open its mouth wide enough to swallow a fish much larger than itself, and then expand its stomach to accommodate its catch. [ 73 ]
Hydrothermal vents along the mid-ocean ridge spreading centers act as oases , as do their opposites, cold seeps . Such places support unique marine biomes and many new marine microorganisms and other lifeforms have been discovered at these locations.
The deepest recorded oceanic trenches measure to date is the Mariana Trench , near the Philippines , in the Pacific Ocean at 10,924 m (35,838 ft). At such depths, water pressure is extreme and there is no sunlight, but some life still exists. A white flatfish , a shrimp and a jellyfish were seen by the American crew of the bathyscaphe Trieste when it dove to the bottom in 1960. [ 74 ]
Marine life also flourishes around seamounts that rise from the depths, where fish and other sea life congregate to spawn and feed.
Mudflats are typically important regions for wildlife, supporting a large population, although levels of biodiversity are not particularly high. They are of particular importance to migratory birds as well as crabs, shrimp, and shellfish. [ 75 ] These areas along the coast act as a nursery for these animals by providing an area for reproduction and feeding. However, this can pose as an issue due to the high trafficking of the birds migrating for nesting, then leaving to return to their seasonal homes. Whatever pollutants the birds take in while breeding are brought back with them to their next location, thus polluting that area as well. [ 76 ] In the United Kingdom mudflats have been classified as a Biodiversity Action Plan priority habitat. European countries such as France have also found it beneficial to use the Marine Influence Index (MII) to be able to monitor the responses to pollution the local plant and animal species may have as well as monitor any type of deviation from the natural patterns displayed previously. [ 77 ]
Although many parts of the seafloor have yet to be explored, researchers have found that parts of it have been greatly affected by human activity. Bottom trawling, microplastic pollution, and industrial metals have slowly changed and altered the composition of the sea floor. Bottom trawling refers to a commercial deep sea fishing technique in which the equipment drags across the sea floor. [ 78 ] This has had an adverse effect on the seafloor as it changes the surface structure and composition. In addition, microplastic pollution has become an increasing problem to the seafloor as plastics and other debris are found in many of the sediments. [ 79 ] Due to the build up of litter, the habitats and environments of organisms on the seafloor are being impacted and changed. This includes industrial facilities dumping new metals and minerals, such as cadmium , onto the seafloor that change the chemical composition of the water and poison the inhabitants. [ 80 ]
There are also negative anthropogenic impacts on deep sea habitats, including trash pollution and chemical pollution. Plastic pollution in particular, is one of the greatest forms of uncontrolled human activity that is visible in our oceans today. [ 81 ] Researchers in the Northwestern south China Sea recorded large plastic-dominated litter piles in submarine canyons . [ 81 ] These durable plastics can diffuse into smaller organisms and are then inadvertently consumed by humans in the food we eat and water we drink. [ 82 ] Another threat to organisms lurking in the deep ocean is ghost fishing, and bycatch . Ghost fishing is the term that refers to any abandoned fishing gear in the ocean that continues to entangle and trap marine organisms. Gill nets for example, have been recorded tangled around deep sea corals and continue ghost fishing for extended periods of time. [ 83 ] | https://en.wikipedia.org/wiki/Marine_habitat |
Marine heat exchangers are no different than non-marine heat exchangers except for the simple fact that they are found aboard ships. Heat exchangers can be used for a wide variety of uses. As the name implies, these can be used for heating as well as cooling. The two primary types of marine heat exchangers used aboard vessels in the maritime industry are plate, and shell and tube. Maintenance for heat exchangers prevents fouling and galvanic corrosion from dissimilar metals.
Though there are many more types of heat exchangers that are used shore side, plate and shell and tube heat exchangers are the most common type of heat exchangers found aboard ocean-going vessels.
Plate-type marine heat exchangers are designed with sets of multiple parallel plates that are compressed to form the main cooler unit. This type has a small footprint in comparison to other types of heat exchangers. The plates are designed in such a way that when placed next to each other they create passageways to the fluid to flow between the plates. Gaskets are placed around the edge of each plate in order to prevent the mixing of the two fluids. Due to the temperature and pressure constraints of the rubber used to make the gaskets plate type heat exchangers are used for low pressure, low temperature applications, under 290 psig (20 bar) and 300 degrees Fahrenheit (150 degrees Celsius). [ 1 ]
Shell and tube heat exchangers consist of a tube bundle which is placed inside the larger shell. [ 2 ] Due to this design these exchanger require twice the footprint of the plate heat exchanger in order to perform maintenance. Depending on the amount of cooling needed, shell and tube heat exchangers can be built in single or double pass configuration. The number of pass refers to the number of times the fluid in the shell passes by the fluid in the tubes. This is achieved by placing baffles in the shell that allow for the fluid to be directed.
Heat exchangers on board vessels are used throughout many system. Systems that use heat exchangers include lube oil, jacket water, steam systems and main seawater. The systems are often interconnected by heat exchangers in order to remove heat generated from running equipment from the engine room.
Heat generated due to friction is carried away from the engine in the motor oil . The motor oil flows through a heat exchanger, where the heat is passed to a central engine room cooling loop, before the heat is rejected to the ocean.
Heat generated an engine's cylinders is transferred to a jacket water cooling system through the cylinder wall. In addition to cooling the cylinder walls, jacket water is often found as an insulator between the exhaust header and the engine room. Jacket water cooling systems can be cooled by a central cooling water loop or can be cooled directly by seawater.
Unlike most systems with heat exchangers, steam is used to heat other systems. This is most common when a ship is left pierside for an extended period of time. The steam system will be used to prevent condensation and rusting of vital engine room components. These heat exchangers are most often shell and tube heat exchangers due to the high temperature and pressures often utilized in steam systems.
Seawater cooling is often the last stage of cooling on board a ship. These coolers are oftentimes the largest on board a vessel in order to ensure maximum heat transfer to the seawater. The seawater is then discharged overboard after passing through the coolers.
Maintenance of marine heat exchangers is important to ensure the small pathways in both types of coolers do not become fouled . Depending on the system different types fouling may occur. In oil based systems, an insufficient amount of cooling medium or inefficient flow of oil through the heater can cause the heater to become fouled. Seawater coolers can often become fouled due to marine life present in the water or due to galvanic corrosion if the correct safety measures are not taken to prevent such occurrences.
Regular maintenance of heat exchangers is important in order to maintain the heat exchanger's maximum efficiency. Sacrificial anodes are necessary in cooling systems to prevent galvanic corrosion. Anodes are often time made of Zinc and are replaced when they reach fifty percent wear. Shell and tube heat exchangers require tubes to be plugged upon the detection of a leak. This prevents the two liquids from mixing inside the heat exchangers. In order to perform regular maintenance on a plate type heat exchanger, the plate stack is separated and the plates a cleaned to improve heat transfer. [ 3 ] | https://en.wikipedia.org/wiki/Marine_heat_exchanger |
Marine larval ecology is the study of the factors influencing dispersing larvae , which many marine invertebrates and fishes have. Marine animals with a larva typically release many larvae into the water column, where the larvae develop before metamorphosing into adults.
Marine larvae can disperse over long distances, although determining the actual distance is challenging, because of their size and the lack of a good tracking method. Knowing dispersal distances is important for managing fisheries , effectively designing marine reserves, and controlling invasive species .
Larval dispersal is one of the most important topics in marine ecology , today. Many marine invertebrates and many fishes have a bi-phasic life cycle with a pelagic larva or pelagic eggs that can be transported over long distances, and a demersal or benthic adult. [ 1 ] There are several theories behind why these organisms have evolved this biphasic life history: [ 2 ]
Dispersing as pelagic larvae can be risky. For example, while larvae do avoid benthic predators, they are still exposed to pelagic predators in the water column.
Marine larvae develop via one of three strategies: Direct, lecithotrophic, or planktotrophic. Each strategy has risks of predation and the difficulty of finding a good settlement site.
Direct developing larvae look like the adult. They have typically very low dispersal potential, and are known as "crawl-away larvae", because they crawl away from their egg after hatching. Some species of frogs and snails hatch this way.
Lecithotrophic larvae have greater dispersal potential than direct developers. Many fish species and some benthic invertebrates have lecithotrophic larvae, which have yolk droplets or a yolk sac for nutrition during dispersal. Though some lecithotrophic species can feed in the water column, too. But many, such as tunicates , cannot, and so must settle before depleting their yolk. Consequently, these species have short pelagic larval durations and do not disperse long distances.
Planktotrophic larvae feed while they are in the water column and can be over a long time pelagic and so disperse over long distances. This disperse ability is a key adaptation of benthic marine invertebrates. [ 3 ] Planktotrophic larvae feed on phytoplankton and small zooplankton , including other larvae. Planktotrophic development is the most common type of larval development, especially among benthic invertebrates.
Because planktotrophic larvae are for a long time in the water column and recruit successfully with low probability, early researchers developed the "lottery hypothesis", which states that animals release huge numbers of larvae to increase the chances that at least one will survive, and that larvae cannot influence their probability of success. [ 4 ] [ 5 ] [ 6 ] This hypothesis views larval survival and successful recruitment as chance events, which numerous studies on larval behavior and ecology have since shown to be false. [ 7 ] Though it has been generally disproved, the larval lottery hypothesis represents an important understanding of the difficulties faced by larvae during their time in the water column.
Predation is a major threat to marine larvae, which are an important food source for many organisms. Invertebrate larvae in estuaries are particularly at risk because estuaries are nursery grounds for planktivorous fishes . Larvae have evolved strategies to cope with this threat, including direct defense and avoidance .
Direct defense can include protective structures and chemical defenses. [ 8 ] Most planktivorous fishes are gape-limited predators, meaning their prey is determined by the width of their open mouths, making larger larvae difficult to ingest. [ 9 ] One study proved that spines serve a protective function by removing spines from estuarine crab larvae and monitoring differences in predation rates between de-spined and intact larvae. [ 10 ] The study also showed that predator defense is also behavioral, as they can keep spines relaxed but erect them in the presence of predators. [ 10 ]
Larvae can avoid predators on small and large spatial scales. Some larvae do this by sinking when approached by a predator. A more common avoidance strategy is to become active at night and remain hidden during the day to avoid visual predators. Most larvae and plankton undertake diel vertical migrations between deeper waters with less light and fewer predators during the day and shallow waters in the photic zone at night, where microalgae is abundant. [ 11 ] Estuarine invertebrate larvae avoid predators by developing in the open ocean, where there are fewer predators. This is done using reverse tidal vertical migrations. Larvae use tidal cycles and estuarine flow regimes to aid their departure to the ocean, a process that is well-studied in many estuarine crab species. [ 12 ] [ 13 ] [ 14 ] [ 15 ]
An example of reverse tidal migration performed by crab species would begin with larvae being released on a nocturnal spring high tide to limit predation by planktivorous fishes. As the tide begins to ebbs, larvae swim to the surface to be carried away from the spawning site. When the tide begins to flood , larvae swim to the bottom, where water moves more slowly due to the boundary layer . When the tide again changes back to ebb, the larvae swim to the surface waters and resume their journey to the ocean. Depending on the length of the estuary and the speed of the currents , this process can take anywhere from one tidal cycle to several days. [ 16 ]
The most widely accepted theory explaining the evolution of a pelagic larval stage is the need for long-distance dispersal ability. [ 17 ] [ 18 ] Sessile and sedentary organisms such as barnacles , tunicates, and mussels require a mechanism to move their young into new territory, since they cannot move long distances as adults. Many species have relatively long pelagic larval durations on the order of weeks or months. [ 19 ] [ 20 ] During this time, larvae feed and grow, and many species metamorphose through several stages of development. For example, barnacles molt through six naupliar stages before becoming a cyprid and seeking appropriate settlement substrate. [ 21 ]
This strategy can be risky. Some larvae have been shown to be able to delay their final metamorphosis for a few days or weeks, and most species cannot delay it at all. [ 22 ] [ 23 ] If these larvae metamorphose far from a suitable settlement site, they perish. Many invertebrate larvae have evolved complex behaviors and endogenous rhythms to ensure successful and timely settlement.
Many estuarine species exhibit swimming rhythms of reverse tidal vertical migration to aid in their transport away from their hatching site. Individuals can also exhibit tidal vertical migrations to reenter the estuary when they are competent to settle. [ 24 ]
As larvae reach their final pelagic stage, they become much more tactile ; clinging to anything larger than themselves. One study observed crab postlarvae and found that they would swim vigorously until they encountered a floating object, which they would cling to for the remainder of the experiment. [ 25 ] It was hypothesized that by clinging to floating debris, crabs can be transported towards shore due to the oceanographic forces of internal waves , [ clarification needed ] which carry floating debris shoreward regardless of the prevailing currents.
Once returning to shore, settlers encounter difficulties concerning their actual settlement and recruitment into the population. Space is a limiting factor for sessile invertebrates on rocky shores . Settlers must be wary of adult filter feeders , which cover substrate at settlement sites and eat particles the size of larvae. Settlers must also avoid becoming stranded out of water by waves, and must select a settlement site at the proper tidal height to prevent desiccation and avoid competition and predation . To overcome many of these difficulties, some species rely on chemical cues to assist them in selecting an appropriate settlement site. These cues are usually emitted by adult conspecifics , but some species cue on specific bacterial mats or other qualities of the substrate . [ 26 ] [ 27 ] [ 28 ]
Although with a pelagic larva, many species can increase their dispersal range and decrease the risk of inbreeding , [ 29 ] a larva comes with challenges: Marine larvae risk being washed away without finding a suitable habitat for settlement. Therefore, they have evolved many sensory systems:
Far from shore, larvae are able to use magnetic fields to orient themselves towards the coast over large spatial scales. [ 30 ] [ 31 ] There is additional evidence that species can recognize anomalies in the magnetic field to return to the same location multiple times throughout their life. [ 30 ] Though the mechanisms that these species use is poorly understood, it appears that magnetic fields play an important role in larval orientation offshore, where other cues such as sound and chemicals may be difficult to detect.
Phototaxis (ability to differentiate between light and dark areas) is important to find a suitable habitat. Phototaxis evolved relatively quickly [ 32 ] and taxa that lack developed eyes, such as schyphozoans , use phototaxis to find shaded areas to settle away from predators. [ 33 ]
Phototaxis is not the only mechanism that guides larvae by light. The larvae of the annelid Platynereis dumerilii do not only show positive [ 34 ] and negative phototaxis [ 35 ] over a broad range of the light spectrum, [ 36 ] but swim down to the center of gravity when they are exposed to non-directional UV -light. This behavior is a UV-induced positive gravitaxis . This gravitaxis and negative phototaxis induced by light coming from the water surface form a ratio-metric depth-gauge . [ 37 ] Such a depth gauge is based on the different attenuation of light across the different wavelengths in water. [ 38 ] [ 39 ] In clear water blue light (470 nm) penetrates the deepest. [ 40 ] [ 36 ] And so the larvae need only to compare the two wavelength ranges UV/violet (< 420 nm) and the other wavelengths to find their preferred depth. [ 37 ]
Species that produce more complex larvae, such as fish, can use full vision [ 30 ] to find a suitable habitat on small spatial scales. Larvae of damselfish use vision to find and settle near adults of their species. [ 41 ]
Marine larvae use sound and vibrations to find a good habitat where they can settle and metamorphose into juveniles. This behavior has been seen in fish [ 41 ] as well as in the larvae of scleractinian corals. [ 42 ] Many families of coral reef fish are particularly attracted to high- frequency sounds produced by invertebrates, [ 43 ] which larvae use as an indicator of food availability and complex habitat where they may be protected from predators. It is thought that larvae avoid low frequency sounds because they may be associated with transient fish or predators [ 43 ] and is therefore not a reliable indicator of safe habitat.
The spatial range at which larvae detect and use sound waves is still uncertain, though some evidence suggests that it may only be reliable at very small scales. [ 44 ] There is concern that changes in community structure in nursery habitats , such as seagrass beds, kelp forests, and mangroves , could lead to a collapse in larval recruitment [ 45 ] due to a decrease in sound-producing invertebrates. Other researchers argue that larvae may still successfully find a place to settle even if one cue is unreliable. [ 46 ]
Many marine organisms use olfaction (chemical cues in the form of scent) to locate a safe area to metamorphose at the end of their larval stage. [ 41 ] This has been shown in both vertebrates [ 47 ] and invertebrates . [ 48 ] Research has shown that larvae are able to distinguish between water from the open ocean and water from more suitable nursery habitats such as lagoons [ 47 ] and seagrass beds. [ 49 ] Chemical cues can be extremely useful for larvae, but may not have a constant presence, as water input can depend on currents and tidal flow. [ 50 ]
Recent research in the field of larval sensory biology has begun focusing more on how human impacts and environmental disturbance affect settlement rates and larval interpretation of different habitat cues. Ocean acidification due to anthropogenic climate change and sedimentation have become areas of particular interest.
Although several behaviours of coral reef fish, including larvae, has been found to be detrimentally affected from projected end-of-21st-century ocean acidification in previous experiments, a 2020 replication study found that "end-of-century ocean acidification levels have negligible effects on [three] important behaviours of coral reef fishes" and with "data simulations, [showed] that the large effect sizes and small within-group variances that have been reported in several previous studies are highly improbable". [ 51 ] [ 52 ] In 2021, it emerged that some of the previous studies about coral reef fish behaviour changes have been accused of being fraudulent. [ 53 ] Furthermore, effect sizes of studies assessing ocean acidification effects on fish behaviour have declined dramatically over a decade of research on this topic, with effects appearing negligible since 2015. [ 54 ]
Ocean acidification has been shown to alter the way that pelagic larvae are able to process information [ 55 ] and production of the cues themselves. [ 56 ] Acidification can alter larval interpretations of sounds, particularly in fish, [ 57 ] leading to settlement in suboptimal habitat. Though the mechanism for this process is still not fully understood, some studies indicate that this breakdown may be due to a decrease in size or density of their otoliths. [ 58 ] Furthermore, sounds produced by invertebrates that larvae rely on as an indicator of habitat quality can also change due to acidification. For example, snapping shrimp produce different sounds that larvae may not recognize under acidified conditions due to differences in shell calcification . [ 56 ]
Hearing is not the only sense that may be altered under future ocean chemistry conditions. Evidence also suggests that larval ability to process olfactory cues was also affected when tested under future pH conditions. [ 59 ] Red color cues that coral larvae use to find crustose coralline algae , with which they have a commensal relationship, may also be in danger due to algal bleaching. [ 60 ]
Sediment runoff, from natural storm events or human development, can also impact larval sensory systems and survival. One study focusing on red soil found that increased turbidity due to runoff negatively influenced the ability of fish larvae to interpret visual cues. [ 61 ] More unexpectedly, they also found that red soil can also impair olfactory capabilities. [ 61 ]
Marine ecologists are often interested in the degree of self-recruitment in populations. Historically, larvae were considered passive particles that were carried by ocean currents to faraway locations. This led to the belief that all marine populations were demographically open, connected by long distance larval transport. Recent work has shown that many populations are self-recruiting, and that larvae and juveniles are capable of purposefully returning to their natal sites.
Researchers take a variety of approaches to estimating population connectivity and self-recruitment, and several studies have demonstrated their feasibility. Jones et al. [ 62 ] and Swearer et al., [ 63 ] for example, investigated the proportion of fish larvae returning to their natal reef. Both studies found higher than expected self-recruitment in these populations using mark, release, and recapture sampling. These studies were the first to provide conclusive evidence of self-recruitment in a species with the potential to disperse far from its natal site, and laid the groundwork for numerous future studies. [ 64 ]
Ichthyoplankton have a high mortality rate as they transition their food source from yolk sac to zooplankton. [ 65 ] It is proposed that this mortality rate is related to food supply as well as an inability to move through the water effectively at this stage of development, leading to starvation. Turbidity of water can also impact the organisms' ability to feed even when there is a high density of prey. Reducing hydrodynamic constraints on cultivated populations could lead to higher yields for repopulation efforts and has been proposed as a means of conserving fish populations by acting at the larval level. [ 66 ]
A network of marine reserves has been initiated for the conservation of the world's marine larval populations. These areas restrict fishing and therefore increase the number of otherwise fished species. This leads to a healthier ecosystem and affects the number of overall species within the reserve as compared to nearby fished areas; however, the full effect of an increase in larger predator fish on larval populations is not currently known. Also, the potential for utilizing the motility of fish larvae to repopulate the water surrounding the reserve is not fully understood. Marine reserves are a part of a growing conservation effort to combat overfishing ; however, reserves still only comprise about 1% of the world's oceans. These reserves are also not protected from other human-derived threats, such as chemical pollutants, so they cannot be the only method of conservation without certain levels of protection for the water around them as well. [ 67 ]
For effective conservation, it is important to understand the larval dispersal patterns of the species in danger, as well as the dispersal of invasive species and predators which could impact their populations. Understanding these patterns is an important factor when creating protocol for governing fishing and creating reserves . A single species may have multiple dispersal patterns. The spacing and size of marine reserves must reflect this variability to maximize their beneficial effect. Species with shorter dispersal patterns are more likely to be affected by local changes and require higher priority for conservation because of the separation of subpopulations. [ 68 ]
The principles of marine larval ecology can be applied in other fields, too whether marine or not. Successful fisheries management relies heavily on understanding population connectivity and dispersal distances, which are driven by larvae. Dispersal and connectivity must also be considered when designing natural reserves. If populations are not self-recruiting, reserves may lose their species assemblages. Many invasive species can disperse over long distances, including the seeds of land plants and larvae of marine invasive species. Understanding the factors influencing their dispersal is key to controlling their spread and managing established populations. | https://en.wikipedia.org/wiki/Marine_larval_ecology |
Marine life , sea life or ocean life is the collective ecological communities that encompass all aquatic animals , plants , algae , fungi , protists , single-celled microorganisms and associated viruses living in the saline water of marine habitats , either the sea water of marginal seas and oceans , or the brackish water of coastal wetlands , lagoons , estuaries and inland seas . As of 2023 [update] , more than 242,000 marine species have been documented, and perhaps two million marine species are yet to be documented. An average of 2,332 new species per year are being described. [ 2 ] [ 3 ] Marine life is studied scientifically in both marine biology and in biological oceanography .
By volume, oceans provide about 90% of the living space on Earth , [ 4 ] and served as the cradle of life and vital biotic sanctuaries throughout Earth's geological history . The earliest known life forms evolved as anaerobic prokaryotes ( archaea and bacteria ) in the Archean oceans around the deep sea hydrothermal vents , before photoautotrophs appeared and allowed the microbial mats to expand into shallow water marine environments . The Great Oxygenation Event of the early Proterozoic significantly altered the marine chemistry , which likely caused a widespread anaerobe extinction event but also led to the evolution of eukaryotes through symbiogenesis between surviving anaerobes and aerobes . Complex life eventually arose out of marine eukaryotes during the Neoproterozoic , and which culminated in a large evolutionary radiation event of mostly sessile macrofaunae known as the Avalon Explosion . This was followed in the early Phanerozoic by a more prominent radiation event known as the Cambrian Explosion , where actively moving eumetazoan became prevalent. These marine life also expanded into fresh waters , where fungi and green algae that were washed ashore onto riparian areas started to take hold later during the Ordivician before rapidly expanding inland during the Silurian and Devonian , paving the way for terrestrial ecosystems to develop.
Today, marine species range in size from the microscopic phytoplankton , which can be as small as 0.02– micrometers ; to huge cetaceans like the blue whale , which can reach 33 m (108 ft) in length. [ 5 ] [ 6 ] Marine microorganisms have been variously estimated as constituting about 70% [ 7 ] or about 90% [ 8 ] [ 1 ] of the total marine biomass . Marine primary producers , mainly cyanobacteria and chloroplastic algae , produce oxygen and sequester carbon via photosynthesis , which generate enormous biomass and significantly influence the atmospheric chemistry . Migratory species, such as oceanodromous and anadromous fish , also create biomass and biological energy transfer between different regions of Earth, with many serving as keystone species of various ecosystems. At a fundamental level, marine life affects the nature of the planet, and in part, shape and protect shorelines, and some marine organisms (e.g. corals ) even help create new land via accumulated reef -building.
Marine life can be roughly grouped into autotrophs and heterotrophs according to their roles within the food web : the former include photosynthetic and the much rarer chemosynthetic organisms ( chemoautotrophs ) that can convert inorganic molecules into organic compounds using energy from sunlight or exothermic oxidation , such as cyanobacteria, iron-oxidizing bacteria , algae ( seaweeds and various microalgae ) and seagrass ; the latter include all the rest that must feed on other organisms to acquire nutrients and energy, which include animals, fungi, protists and non-photosynthetic microorganisms. Marine animals are further informally divided into marine vertebrates and marine invertebrates , both of which are polyphyletic groupings with the former including all saltwater fish , marine mammals , marine reptiles and seabirds , and the latter include all that are not considered vertebrates . Generally, marine vertebrates are much more nektonic and metabolically demanding of oxygen and nutrients, often suffering distress or even mass deaths (a.k.a. " fish kills ") during anoxic events , while marine invertebrates are a lot more hypoxia -tolerant and exhibit a wide range of morphological and physiological modifications to survive in poorly oxygenated waters .
There is no life without water. [ 9 ] It has been described as the universal solvent for its ability to dissolve many substances, [ 10 ] [ 11 ] and as the solvent of life . [ 12 ] Water is the only common substance to exist as a solid , liquid, and gas under conditions normal to life on Earth. [ 13 ] The Nobel Prize winner Albert Szent-Györgyi referred to water as the mater und matrix : the mother and womb of life. [ 14 ]
The abundance of surface water on Earth is a unique feature in the Solar System . Earth's hydrosphere consists chiefly of the oceans but technically includes all water surfaces in the world, including inland seas, lakes, rivers, and underground waters down to a depth of 2,000 metres (6,600 ft). The deepest underwater location is Challenger Deep of the Mariana Trench in the Pacific Ocean , having a depth of 10,900 metres (6.8 mi). [ note 1 ] [ 15 ]
Conventionally, the planet is divided into five separate oceans, but these oceans all connect into a single world ocean . [ 16 ] The mass of this world ocean is 1.35 × 10 18 metric tons or about 1/4400 of Earth's total mass. The world ocean covers an area of 3.618 × 10 8 km 2 with a mean depth of 3682 m , resulting in an estimated volume of 1.332 × 10 9 km 3 . [ 17 ] If all of Earth's crustal surface was at the same elevation as a smooth sphere, the depth of the resulting world ocean would be about 2.7 kilometres (1.7 mi). [ 18 ] [ 19 ]
About 97.5% of the water on Earth is saline ; the remaining 2.5% is fresh water . Most fresh water – about 69% – is present as ice in ice caps and glaciers . [ 20 ] The average salinity of Earth's oceans is about 35 grams (1.2 oz) of salt per kilogram of seawater (3.5% salt). [ 21 ] Most of the salt in the ocean comes from the weathering and erosion of rocks on land. [ 22 ] Some salts are released from volcanic activity or extracted from cool igneous rocks . [ 23 ]
The oceans are also a reservoir of dissolved atmospheric gases, which are essential for the survival of many aquatic life forms. [ 24 ] Sea water has an important influence on the world's climate, with the oceans acting as a large heat reservoir . [ 25 ] Shifts in the oceanic temperature distribution can cause significant weather shifts, such as the El Niño-Southern Oscillation . [ 26 ]
Altogether the ocean occupies 71 percent of the world surface, [ 4 ] averaging nearly 3.7 kilometres (2.3 mi) in depth. [ 27 ] By volume, the ocean provides about 90 percent of the living space on the planet. [ 4 ] The science fiction writer Arthur C. Clarke has pointed out it would be more appropriate to refer to planet Earth as planet Ocean. [ 28 ] [ 29 ]
However, water is found elsewhere in the Solar System. Europa , one of the moons orbiting Jupiter , is slightly smaller than the Earth's Moon . There is a strong possibility a large saltwater ocean exists beneath its ice surface. [ 30 ] It has been estimated the outer crust of solid ice is about 10–30 km (6–19 mi) thick and the liquid ocean underneath is about 100 km (60 mi) deep. [ 31 ] This would make Europa's ocean over twice the volume of the Earth's ocean. There has been speculation Europa's ocean could support life , [ 32 ] [ 33 ] and could be capable of supporting multicellular microorganisms if hydrothermal vents are active on the ocean floor. [ 34 ] Enceladus , a small icy moon of Saturn, also has what appears to be an underground ocean which actively vents warm water from the moon's surface. [ 35 ]
The Earth is about 4.54 billion years old. [ 36 ] [ 37 ] [ 38 ] The earliest undisputed evidence of life on Earth dates from at least 3.5 billion years ago, [ 39 ] [ 40 ] during the Eoarchean era after a geological crust started to solidify following the earlier molten Hadean Eon. Microbial mat fossils have been found in 3.48 billion-year-old sandstone in Western Australia . [ 41 ] [ 42 ] Other early physical evidence of a biogenic substance is graphite in 3.7 billion-year-old metasedimentary rocks discovered in Western Greenland [ 43 ] as well as "remains of biotic life " found in 4.1 billion-year-old rocks in Western Australia. [ 44 ] [ 45 ] According to one of the researchers, "If life arose relatively quickly on Earth … then it could be common in the universe ." [ 44 ]
All organisms on Earth are descended from a common ancestor or ancestral gene pool . [ 46 ] [ 47 ] Highly energetic chemistry is thought to have produced a self-replicating molecule around 4 billion years ago, and half a billion years later the last common ancestor of all life existed. [ 48 ] The current scientific consensus is that the complex biochemistry that makes up life came from simpler chemical reactions. [ 49 ] The beginning of life may have included self-replicating molecules such as RNA [ 50 ] and the assembly of simple cells. [ 51 ] In 2016 scientists reported a set of 355 genes from the last universal common ancestor (LUCA) of all life , including microorganisms, living on Earth . [ 52 ]
Current species are a stage in the process of evolution, with their diversity the product of a long series of speciation and extinction events. [ 53 ] The common descent of organisms was first deduced from four simple facts about organisms: First, they have geographic distributions that cannot be explained by local adaptation. Second, the diversity of life is not a set of unique organisms, but organisms that share morphological similarities . Third, vestigial traits with no clear purpose resemble functional ancestral traits and finally, that organisms can be classified using these similarities into a hierarchy of nested groups—similar to a family tree. [ 54 ] However, modern research has suggested that, due to horizontal gene transfer , this "tree of life" may be more complicated than a simple branching tree since some genes have spread independently between distantly related species. [ 55 ] [ 56 ]
Past species have also left records of their evolutionary history. Fossils, along with the comparative anatomy of present-day organisms, constitute the morphological, or anatomical, record. [ 57 ] By comparing the anatomies of both modern and extinct species, paleontologists can infer the lineages of those species. However, this approach is most successful for organisms that had hard body parts, such as shells, bones or teeth. Further, as prokaryotes such as bacteria and archaea share a limited set of common morphologies, their fossils do not provide information on their ancestry.
More recently, evidence for common descent has come from the study of biochemical similarities between organisms. For example, all living cells use the same basic set of nucleotides and amino acids . [ 59 ] The development of molecular genetics has revealed the record of evolution left in organisms' genomes: dating when species diverged through the molecular clock produced by mutations. [ 60 ] For example, these DNA sequence comparisons have revealed that humans and chimpanzees share 98% of their genomes and analyzing the few areas where they differ helps shed light on when the common ancestor of these species existed. [ 61 ]
Prokaryotes inhabited the Earth from approximately 3–4 billion years ago. [ 62 ] [ 63 ] No obvious changes in morphology or cellular organization occurred in these organisms over the next few billion years. [ 64 ] The eukaryotic cells emerged between 1.6 and 2.7 billion years ago. The next major change in cell structure came when bacteria were engulfed by eukaryotic cells, in a cooperative association called endosymbiosis . [ 65 ] [ 66 ] The engulfed bacteria and the host cell then underwent coevolution, with the bacteria evolving into either mitochondria or hydrogenosomes . [ 67 ] Another engulfment of cyanobacterial -like organisms led to the formation of chloroplasts in algae and plants. [ 68 ]
The history of life was that of the unicellular eukaryotes, prokaryotes and archaea until about 610 million years ago when multicellular organisms began to appear in the oceans in the Ediacaran period. [ 62 ] [ 69 ] The evolution of multicellularity occurred in multiple independent events, in organisms as diverse as sponges , brown algae , cyanobacteria , slime moulds and myxobacteria . [ 70 ] In 2016 scientists reported that, about 800 million years ago, a minor genetic change in a single molecule called GK-PID may have allowed organisms to go from a single cell organism to one of many cells. [ 71 ]
Soon after the emergence of these first multicellular organisms, a remarkable amount of biological diversity appeared over a span of about 10 million years, in an event called the Cambrian explosion . Here, the majority of types of modern animals appeared in the fossil record, as well as unique lineages that subsequently became extinct. [ 72 ] Various triggers for the Cambrian explosion have been proposed, including the accumulation of oxygen in the atmosphere from photosynthesis. [ 73 ]
About 500 million years ago, plants and fungi started colonizing the land. Evidence for the appearance of the first land plants occurs in the Ordovician , around 450 million years ago , in the form of fossil spores. [ 74 ] Land plants began to diversify in the Late Silurian , from around 430 million years ago . [ 75 ] The colonization of the land by plants was soon followed by arthropods and other animals. [ 76 ] Insects were particularly successful and even today make up the majority of animal species. [ 77 ] Amphibians first appeared around 364 million years ago, followed by early amniotes and birds around 155 million years ago (both from " reptile "-like lineages), mammals around 129 million years ago, homininae around 10 million years ago and modern humans around 250,000 years ago. [ 78 ] [ 79 ] [ 80 ] However, despite the evolution of these large animals, smaller organisms similar to the types that evolved early in this process continue to be highly successful and dominate the Earth, with the majority of both biomass and species being prokaryotes. [ 81 ]
Estimates on the number of Earth's current species range from 10 million to 14 million, [ 82 ] of which about 1.2 million have been documented and over 86 percent have not yet been described. [ 83 ]
Microorganisms make up about 70% of the marine biomass . [ 7 ] A microorganism , or microbe, is a microscopic organism too small to be recognized with the naked eye. It can be single-celled [ 84 ] or multicellular . Microorganisms are diverse and include all bacteria and archaea , most protozoa such as algae , fungi , and certain microscopic animals such as rotifers .
Many macroscopic animals and plants have microscopic juvenile stages . Some microbiologists also classify viruses (and viroids ) as microorganisms, but others consider these as nonliving. [ 85 ] [ 86 ]
Microorganisms are crucial to nutrient recycling in ecosystems as they act as decomposers . Some microorganisms are pathogenic , causing disease and even death in plants and animals. [ 87 ] As inhabitants of the largest environment on Earth, microbial marine systems drive changes in every global system. Microbes are responsible for virtually all the photosynthesis that occurs in the ocean, as well as the cycling of carbon , nitrogen , phosphorus , other nutrients and trace elements. [ 88 ]
Viruses
Bacteria
Archaea
Protists
Microfungi
Microanimals
Microscopic life undersea is diverse and still poorly understood, such as for the role of viruses in marine ecosystems. [ 89 ] Most marine viruses are bacteriophages , which are harmless to plants and animals, but are essential to the regulation of saltwater and freshwater ecosystems. [ 90 ] : 5 They infect and destroy bacteria in aquatic microbial communities, and are the most important mechanism of recycling carbon in the marine environment. The organic molecules released from the dead bacterial cells stimulate fresh bacterial and algal growth. [ 90 ] : 593 Viral activity may also contribute to the biological pump , the process whereby carbon is sequestered in the deep ocean. [ 91 ]
A stream of airborne microorganisms circles the planet above weather systems but below commercial air lanes. [ 92 ] Some peripatetic microorganisms are swept up from terrestrial dust storms, but most originate from marine microorganisms in sea spray . In 2018, scientists reported that hundreds of millions of viruses and tens of millions of bacteria are deposited daily on every square meter around the planet. [ 93 ] [ 94 ]
Microscopic organisms live throughout the biosphere . The mass of prokaryote microorganisms — which includes bacteria and archaea, but not the nucleated eukaryote microorganisms — may be as much as 0.8 trillion tons of carbon (of the total biosphere mass , estimated at between 1 and 4 trillion tons). [ 95 ] Single-celled barophilic marine microbes have been found at a depth of 10,900 m (35,800 ft) in the Mariana Trench , the deepest spot in the Earth's oceans. [ 96 ] [ 97 ] Microorganisms live inside rocks 580 m (1,900 ft) below the sea floor under 2,590 m (8,500 ft) of ocean off the coast of the northwestern United States, [ 96 ] [ 98 ] as well as 2,400 m (7,900 ft; 1.5 mi) beneath the seabed off Japan. [ 99 ] The greatest known temperature at which microbial life can exist is 122 °C (252 °F) ( Methanopyrus kandleri ). [ 100 ] In 2014, scientists confirmed the existence of microorganisms living 800 m (2,600 ft) below the ice of Antarctica . [ 101 ] [ 102 ] According to one researcher, "You can find microbes everywhere — they're extremely adaptable to conditions, and survive wherever they are." [ 96 ]
Viruses are small infectious agents that do not have their own metabolism and can replicate only inside the living cells of other organisms . [ 103 ] Viruses can infect all types of life forms , from animals and plants to microorganisms , including bacteria and archaea . [ 104 ] The linear size of the average virus is about one one-hundredth that of the average bacterium . Most viruses cannot be seen with an optical microscope so electron microscopes are used instead. [ 105 ]
Viruses are found wherever there is life and have probably existed since living cells first evolved. [ 106 ] The origin of viruses is unclear because they do not form fossils, so molecular techniques have been used to compare the DNA or RNA of viruses and are a useful means of investigating how they arise. [ 107 ]
Viruses are now recognized as ancient and as having origins that pre-date the divergence of life into the three domains . [ 108 ] But the origins of viruses in the evolutionary history of life are unclear: some may have evolved from plasmids —pieces of DNA that can move between cells—while others may have evolved from bacteria. In evolution, viruses are an important means of horizontal gene transfer , which increases genetic diversity . [ 109 ]
Opinions differ on whether viruses are a form of life or organic structures that interact with living organisms. [ 110 ] They are considered by some to be a life form, because they carry genetic material, reproduce by creating multiple copies of themselves through self-assembly, and evolve through natural selection . However they lack key characteristics such as a cellular structure generally considered necessary to count as life. Because they possess some but not all such qualities, viruses have been described as replicators [ 110 ] and as "organisms at the edge of life". [ 111 ]
Bacteriophages , often just called phages , are viruses that parasite bacteria and archaea. Marine phages parasite marine bacteria and archaea, such as cyanobacteria . [ 112 ] They are a common and diverse group of viruses and are the most abundant biological entity in marine environments, because their hosts, bacteria, are typically the numerically dominant cellular life in the sea. Generally there are about 1 million to 10 million viruses in each mL of seawater, or about ten times more double-stranded DNA viruses than there are cellular organisms, [ 113 ] [ 114 ] although estimates of viral abundance in seawater can vary over a wide range. [ 115 ] [ 116 ] Tailed bacteriophages appear to dominate marine ecosystems in number and diversity of organisms. [ 112 ] Bacteriophages belonging to the families Corticoviridae , [ 117 ] Inoviridae [ 118 ] and Microviridae [ 119 ] are also known to infect diverse marine bacteria.
Microorganisms make up about 70% of the marine biomass. [ 7 ] It is estimated viruses kill 20% of this biomass each day and that there are 15 times as many viruses in the oceans as there are bacteria and archaea. Viruses are the main agents responsible for the rapid destruction of harmful algal blooms , [ 114 ] which often kill other marine life. [ 120 ] The number of viruses in the oceans decreases further offshore and deeper into the water, where there are fewer host organisms. [ 91 ]
There are also archaeal viruses which replicate within archaea : these are double-stranded DNA viruses with unusual and sometimes unique shapes. [ 121 ] [ 122 ] These viruses have been studied in most detail in the thermophilic archaea, particularly the orders Sulfolobales and Thermoproteales . [ 123 ]
Viruses are an important natural means of transferring genes between different species, which increases genetic diversity and drives evolution. [ 109 ] It is thought that viruses played a central role in the early evolution, before the diversification of bacteria, archaea and eukaryotes, at the time of the last universal common ancestor of life on Earth. [ 124 ] Viruses are still one of the largest reservoirs of unexplored genetic diversity on Earth. [ 91 ]
Bacteria constitute a large domain of prokaryotic microorganisms . Typically a few micrometers in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth , and are present in most of its habitats . Bacteria inhabit soil, water, acidic hot springs , radioactive waste , [ 125 ] and the deep portions of Earth's crust . Bacteria also live in symbiotic and parasitic relationships with plants and animals.
Once regarded as plants constituting the class Schizomycetes , bacteria are now classified as prokaryotes . Unlike cells of animals and other eukaryotes , bacterial cells do not contain a nucleus and rarely harbor membrane-bound organelles . Although the term bacteria traditionally included all prokaryotes, the scientific classification changed after the discovery in the 1990s that prokaryotes consist of two very different groups of organisms that evolved from an ancient common ancestor. These evolutionary domains are called Bacteria and Archaea . [ 126 ]
The ancestors of modern bacteria were unicellular microorganisms that were the first forms of life to appear on Earth, about 4 billion years ago. For about 3 billion years, most organisms were microscopic, and bacteria and archaea were the dominant forms of life. [ 64 ] [ 127 ] Although bacterial fossils exist, such as stromatolites , their lack of distinctive morphology prevents them from being used to examine the history of bacterial evolution, or to date the time of origin of a particular bacterial species. However, gene sequences can be used to reconstruct the bacterial phylogeny , and these studies indicate that bacteria diverged first from the archaeal/eukaryotic lineage. [ 128 ] Bacteria were also involved in the second great evolutionary divergence, that of the archaea and eukaryotes. Here, eukaryotes resulted from the entering of ancient bacteria into endosymbiotic associations with the ancestors of eukaryotic cells, which were themselves possibly related to the Archaea . [ 66 ] [ 65 ] This involved the engulfment by proto-eukaryotic cells of alphaproteobacterial symbionts to form either mitochondria or hydrogenosomes , which are still found in all known Eukarya. Later on, some eukaryotes that already contained mitochondria also engulfed cyanobacterial-like organisms. This led to the formation of chloroplasts in algae and plants. There are also some algae that originated from even later endosymbiotic events. Here, eukaryotes engulfed a eukaryotic algae that developed into a "second-generation" plastid. [ 129 ] [ 130 ] This is known as secondary endosymbiosis .
The largest known bacterium, the marine Thiomargarita namibiensis , can be visible to the naked eye and sometimes attains 0.75 mm (750 μm). [ 132 ] [ 133 ]
The archaea (Greek for ancient [ 134 ] ) constitute a domain and kingdom of single-celled microorganisms . These microbes are prokaryotes , meaning they have no cell nucleus or any other membrane-bound organelles in their cells.
Archaea were initially classified as bacteria , but this classification is outdated. [ 135 ] Archaeal cells have unique properties separating them from the other two domains of life, Bacteria and Eukaryota . The Archaea are further divided into multiple recognized phyla . Classification is difficult because the majority have not been isolated in the laboratory and have only been detected by analysis of their nucleic acids in samples from their environment.
Archaea and bacteria are generally similar in size and shape, although a few archaea have very strange shapes, such as the flat and square-shaped cells of Haloquadratum walsbyi . [ 136 ] Despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably the enzymes involved in transcription and translation . Other aspects of archaeal biochemistry are unique, such as their reliance on ether lipids in their cell membranes , such as archaeols . Archaea use more energy sources than eukaryotes: these range from organic compounds , such as sugars, to ammonia , metal ions or even hydrogen gas . Salt-tolerant archaea (the Haloarchaea ) use sunlight as an energy source, and other species of archaea fix carbon ; however, unlike plants and cyanobacteria , no known species of archaea does both. Archaea reproduce asexually by binary fission , fragmentation , or budding ; unlike bacteria and eukaryotes, no known species forms spores .
Archaea are particularly numerous in the oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet. Archaea are a major part of Earth's life and may play roles in both the carbon cycle and the nitrogen cycle .
Protists are eukaryotes that cannot be classified as plants, fungi or animals. They are usually single-celled and microscopic. Life originated as single-celled prokaryotes ( bacteria and archaea ) and later evolved into more complex eukaryotes . Eukaryotes are the more developed life forms known as plants, animals, fungi and protists. The term protist came into use historically as a term of convenience for eukaryotes that cannot be strictly classified as plants, animals or fungi. They are not a part of modern cladistics, because they are paraphyletic (lacking a common ancestor). Protists can be broadly divided into four groups depending on whether their nutrition is plant-like, animal-like, fungus-like, [ 137 ] or a mixture of these. [ 138 ]
Protists are highly diverse organisms currently organized into 18 phyla, but are not easy to classify. [ 141 ] [ 142 ] Studies have shown high protist diversity exists in oceans, deep sea-vents and river sediments, suggesting a large number of eukaryotic microbial communities have yet to be discovered. [ 143 ] [ 144 ] There has been little research on mixotrophic protists, but recent studies in marine environments found mixotrophic protests contribute a significant part of the protist biomass . [ 139 ]
In contrast to the cells of prokaryotes, the cells of eukaryotes are highly organized. Plants, animals and fungi are usually multi-celled and are typically macroscopic . Most protists are single-celled and microscopic. But there are exceptions. Some single-celled marine protists are macroscopic. Some marine slime molds have unique life cycles that involve switching between unicellular, colonial , and multicellular forms. [ 147 ] Other marine protist are neither single-celled nor microscopic, such as seaweed .
Protists have been described as a taxonomic grab bag where anything that doesn't fit into one of the main biological kingdoms can be placed. [ 149 ] Some modern authors prefer to exclude multicellular organisms from the traditional definition of a protist, restricting protists to unicellular organisms. [ 150 ] [ 151 ] This more constrained definition excludes seaweeds and slime molds . [ 152 ]
As juveniles, animals develop from microscopic stages, which can include spores , eggs and larvae . At least one microscopic animal group, the parasitic cnidarian Myxozoa , is unicellular in its adult form, and includes marine species. Other adult marine microanimals are multicellular. Microscopic adult arthropods are more commonly found inland in freshwater, but there are marine species as well. Microscopic adult marine crustaceans include some copepods , cladocera and tardigrades (water bears). Some marine nematodes and rotifers are also too small to be recognized with the naked eye, as are many loricifera , including the recently discovered anaerobic species that spend their lives in an anoxic environment. [ 153 ] [ 154 ] Copepods contribute more to the secondary productivity and carbon sink of the world oceans than any other group of organisms. [ 155 ] [ 156 ] While mites are not normally thought of as marine organisms, most species of the family Halacaridae live in the sea. [ 157 ]
Over 1500 species of fungi are known from marine environments. [ 158 ] These are parasitic on marine algae or animals, or are saprobes feeding on dead organic matter from algae, corals, protozoan cysts, sea grasses, wood and other substrata. [ 159 ] Spores of many species have special appendages which facilitate attachment to the substratum. [ 160 ] Marine fungi can also be found in sea foam and around hydrothermal areas of the ocean. [ 161 ] A diverse range of unusual secondary metabolites is produced by marine fungi. [ 162 ]
Mycoplankton are saprotropic members of the plankton communities of marine and freshwater ecosystems . [ 163 ] [ 164 ] They are composed of filamentous free-living fungi and yeasts associated with planktonic particles or phytoplankton . [ 165 ] Similar to bacterioplankton , these aquatic fungi play a significant role in heterotrophic mineralization and nutrient cycling . [ 166 ] Mycoplankton can be up to 20 mm in diameter and over 50 mm in length. [ 167 ]
A typical milliliter of seawater contains about 10 3 to 10 4 fungal cells. [ 168 ] This number is greater in coastal ecosystems and estuaries due to nutritional runoff from terrestrial communities. A higher diversity of mycoplankton is found around coasts and in surface waters down to 1000 meters, with a vertical profile that depends on how abundant phytoplankton is. [ 169 ] [ 170 ] This profile changes between seasons due to changes in nutrient availability. [ 171 ] Marine fungi survive in a constant oxygen deficient environment, and therefore depend on oxygen diffusion by turbulence and oxygen generated by photosynthetic organisms . [ 172 ]
Marine fungi can be classified as: [ 172 ]
Lichens are mutualistic associations between a fungus, usually an ascomycete , and an alga or a cyanobacterium . Several lichens are found in marine environments. [ 173 ] Many more occur in the splash zone , where they occupy different vertical zones depending on how tolerant they are to submersion. [ 174 ] Some lichens live a long time; one species has been dated at 8,600 years. [ 175 ] However their lifespan is difficult to measure because what defines the same lichen is not precise. [ 176 ] Lichens grow by vegetatively breaking off a piece, which may or may not be defined as the same lichen, and two lichens of different ages can merge, raising the issue of whether it is the same lichen. [ 176 ] The sea snail Littoraria irrorata damages plants of Spartina in the sea marshes where it lives, which enables spores of intertidal ascomycetous fungi to colonize the plant. The snail then eats the fungal growth in preference to the grass itself. [ 177 ]
According to fossil records, fungi date back to the late Proterozoic era 900–570 million years ago. Fossil marine lichens 600 million years old have been discovered in China. [ 178 ] It has been hypothesized that mycoplankton evolved from terrestrial fungi, likely in the Paleozoic era (390 million years ago). [ 179 ]
The earliest animals were marine invertebrates , that is, vertebrates came later. Animals are multicellular eukaryotes , [ note 2 ] and are distinguished from plants, algae, and fungi by lacking cell walls . [ 180 ] Marine invertebrates are animals that inhabit a marine environment apart from the vertebrate members of the chordate phylum; invertebrates lack a vertebral column . Some have evolved a shell or a hard exoskeleton .
The earliest animal fossils may belong to the genus Dickinsonia , [ 181 ] 571 million to 541 million years ago. [ 182 ] Individual Dickinsonia typically resemble a bilaterally symmetrical ribbed oval. They kept growing until they were covered with sediment or otherwise killed, [ 183 ] and spent most of their lives with their bodies firmly anchored to the sediment. [ 184 ] Their taxonomic affinities are presently unknown, but their mode of growth is consistent with a bilaterian affinity. [ 185 ]
Apart from Dickinsonia , the earliest widely accepted animal fossils are the rather modern-looking cnidarians (the group that includes coral , jellyfish , sea anemones and Hydra ), possibly from around 580 Ma [ 186 ] The Ediacara biota , which flourished for the last 40 million years before the start of the Cambrian , [ 187 ] were the first animals more than a very few centimeters long. Like Dickinsonia , many were flat with a "quilted" appearance, and seemed so strange that there was a proposal to classify them as a separate kingdom , Vendozoa . [ 188 ] Others, however, have been interpreted as early molluscs ( Kimberella [ 189 ] [ 190 ] ), echinoderms ( Arkarua [ 191 ] ), and arthropods ( Spriggina , [ 192 ] Parvancorina [ 193 ] ). There is still debate about the classification of these specimens, mainly because the diagnostic features which allow taxonomists to classify more recent organisms, such as similarities to living organisms, are generally absent in the Ediacarans. However, there seems little doubt that Kimberella was at least a triploblastic bilaterian animal, in other words, an animal significantly more complex than the cnidarians. [ 194 ]
Small shelly fauna are a very mixed collection of fossils found between the Late Ediacaran and Middle Cambrian periods. The earliest, Cloudina , shows signs of successful defense against predation and may indicate the start of an evolutionary arms race . Some tiny Early Cambrian shells almost certainly belonged to molluscs, while the owners of some "armor plates," Halkieria and Microdictyon , were eventually identified when more complete specimens were found in Cambrian lagerstätten that preserved soft-bodied animals. [ 195 ]
Invertebrates are grouped into different phyla . Informally phyla can be thought of as a way of grouping organisms according to their body plan . [ 196 ] [ 197 ] : 33 A body plan refers to a blueprint which describes the shape or morphology of an organism, such as its symmetry , segmentation and the disposition of its appendages . The idea of body plans originated with vertebrates , which were grouped into one phylum. But the vertebrate body plan is only one of many, and invertebrates consist of many phyla or body plans. The history of the discovery of body plans can be seen as a movement from a worldview centered on vertebrates, to seeing the vertebrates as one body plan among many. Among the pioneering zoologists , Linnaeus identified two body plans outside the vertebrates; Cuvier identified three; and Haeckel had four, as well as the Protista with eight more, for a total of twelve. For comparison, the number of phyla recognized by modern zoologists has risen to 35 . [ 197 ]
Historically body plans were thought of as having evolved rapidly during the Cambrian explosion , [ 200 ] but a more nuanced understanding of animal evolution suggests a gradual development of body plans throughout the early Palaeozoic and beyond. [ 201 ] More generally a phylum can be defined in two ways: as described above, as a group of organisms with a certain degree of morphological or developmental similarity (the phenetic definition), or a group of organisms with a certain degree of evolutionary relatedness (the phylogenetic definition). [ 201 ]
In the 1970s there was already a debate about whether the emergence of the modern phyla was "explosive" or gradual but hidden by the shortage of Precambrian animal fossils. [ 195 ] A re-analysis of fossils from the Burgess Shale lagerstätte increased interest in the issue when it revealed animals, such as Opabinia , which did not fit into any known phylum . At the time these were interpreted as evidence that the modern phyla had evolved very rapidly in the Cambrian explosion and that the Burgess Shale's "weird wonders" showed that the Early Cambrian was a uniquely experimental period of animal evolution. [ 202 ] Later discoveries of similar animals and the development of new theoretical approaches led to the conclusion that many of the "weird wonders" were evolutionary "aunts" or "cousins" of modern groups [ 203 ] —for example that Opabinia was a member of the lobopods , a group which includes the ancestors of the arthropods, and that it may have been closely related to the modern tardigrades . [ 204 ] Nevertheless, there is still much debate about whether the Cambrian explosion was really explosive and, if so, how and why it happened and why it appears unique in the history of animals. [ 205 ]
The deepest-branching animals — the earliest animals that appeared during evolution — are marine non-vertebrate organisms. The earliest animal phyla are the Porifera , Ctenophora , Placozoa and Cnidaria . No member of these clades exhibit body plans with bilateral symmetry .
Choanoflagellata unicellular protists thought to be the closest living relatives of animals
Porifera sponges – asymmetric
Ctenophora comb jellies – biradial symmetry
Placozoa simplest animals – asymmetric
Cnidaria have tentacles with stingers – radial symmetry
bilaterians all remaining animals – bilateral symmetry →
Sponges are animals of the phylum Porifera (from Modern Latin for bearing pores [ 209 ] ). They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through them, consisting of jelly-like mesohyl sandwiched between two thin layers of cells . They have non-specialized cells that can transform into other types and that often migrate between the main cell layers and the mesohyl in the process. Sponges do not have nervous , digestive or circulatory systems . Instead, most rely on maintaining a constant water flow through their bodies to obtain food and oxygen and to remove wastes.
Sponges are similar to other animals in that they are multicellular , heterotrophic , lack cell walls and produce sperm cells . Unlike other animals, they lack true tissues and organs , and have no body symmetry . The shapes of their bodies are adapted for maximal efficiency of water flow through the central cavity, where it deposits nutrients, and leaves through a hole called the osculum . Many sponges have internal skeletons of spongin and/or spicules of calcium carbonate or silicon dioxide . All sponges are sessile aquatic animals. Although there are freshwater species, the great majority are marine (salt water) species, ranging from tidal zones to depths exceeding 8,800 m (5.5 mi). Some sponges live to great ages; there is evidence of the deep-sea glass sponge Monorhaphis chuni living about 11,000 years. [ 210 ] [ 211 ]
While most of the approximately 5,000–10,000 known species feed on bacteria and other food particles in the water, some host photosynthesizing micro-organisms as endosymbionts and these alliances often produce more food and oxygen than they consume. A few species of sponge that live in food-poor environments have become carnivores that prey mainly on small crustaceans . [ 212 ]
Linnaeus mistakenly identified sponges as plants in the order Algae . [ 213 ] For a long time thereafter sponges were assigned to a separate subkingdom, Parazoa (meaning beside the animals ). [ 214 ] They are now classified as a paraphyletic phylum from which the higher animals have evolved. [ 215 ]
Ctenophores (from Greek for carrying a comb ), commonly known as comb jellies, are a phylum that live worldwide in marine waters. They are the largest non-colonial animals to swim with the help of cilia (hairs or combs). [ 216 ] Coastal species need to be tough enough to withstand waves and swirling sediment, but some oceanic species are so fragile and transparent that it is very difficult to capture them intact for study. [ 217 ] In the past ctenophores were thought to have only a modest presence in the ocean, but it is now known they are often significant and even dominant parts of the planktonic biomass. [ 218 ] : 269
The phylum has about 150 known species with a wide range of body forms. Sizes range from a few millimeters to 1.5 m (4 ft 11 in). Cydippids are egg-shaped with their cilia arranged in eight radial comb rows, and deploy retractable tentacles for capturing prey. The benthic platyctenids are generally combless and flat. The coastal beroids have gaping mouths and lack tentacles. Most adult ctenophores prey on microscopic larvae and rotifers and small crustaceans but beroids prey on other ctenophores.
Early writers combined ctenophores with cnidarians . Ctenophores resemble cnidarians in relying on water flow through the body cavity for both digestion and respiration, as well as in having a decentralized nerve net rather than a brain. Also like cnidarians, the bodies of ctenophores consist of a mass of jelly, with one layer of cells on the outside and another lining the internal cavity. In ctenophores, however, these layers are two cells deep, while those in cnidarians are only a single cell deep. While cnidarians exhibit radial symmetry , ctenophores have two anal canals which exhibit biradial symmetry (half-turn rotational symmetry). [ 219 ] The position of the ctenophores in the evolutionary family tree of animals has long been debated, and the majority view at present, based on molecular phylogenetics , is that cnidarians and bilaterians are more closely related to each other than either is to ctenophores. [ 218 ] : 222
Placozoa (from Greek for flat animals ) have the simplest structure of all animals. They are a basal form of free-living (non-parasitic) multicellular organism [ 220 ] that do not yet have a common name. [ 221 ] They live in marine environments and form a phylum containing so far only three described species, of which the first, the classical Trichoplax adhaerens , was discovered in 1883. [ 222 ] Two more species have been discovered since 2017, [ 223 ] [ 224 ] and genetic methods indicate this phylum has a further 100 to 200 undescribed species . [ 225 ]
Trichoplax is a small, flattened, animal about one mm across and usually about 25 μm thick. Like the amoebae they superficially resemble, they continually change their external shape. In addition, spherical phases occasionally form which may facilitate movement. Trichoplax lacks tissues and organs. There is no manifest body symmetry, so it is not possible to distinguish anterior from posterior or left from right. It is made up of a few thousand cells of six types in three distinct layers. [ 226 ] The outer layer of simple epithelial cells bear cilia which the animal uses to help it creep along the seafloor. [ 227 ] Trichoplax feed by engulfing and absorbing food particles – mainly microbes and organic detritus – with their underside.
Cnidarians (from Greek for nettle ) are distinguished by the presence of stinging cells , specialized cells that they use mainly for capturing prey. Cnidarians include corals , sea anemones , jellyfish and hydrozoans . They form a phylum containing over 10,000 [ 228 ] species of animals found exclusively in aquatic (mainly marine) environments. Their bodies consist of mesoglea , a non-living jelly-like substance, sandwiched between two layers of epithelium that are mostly one cell thick . They have two basic body forms: swimming medusae and sessile polyps , both of which are radially symmetrical with mouths surrounded by tentacles that bear cnidocytes. Both forms have a single orifice and body cavity that are used for digestion and respiration .
Fossil cnidarians have been found in rocks formed about 580 million years ago . Fossils of cnidarians that do not build mineralized structures are rare. Scientists currently think cnidarians, ctenophores and bilaterians are more closely related to calcareous sponges than these are to other sponges , and that anthozoans are the evolutionary "aunts" or "sisters" of other cnidarians, and the most closely related to bilaterians.
Cnidarians are the simplest animals in which the cells are organized into tissues. [ 229 ] The starlet sea anemone is used as a model organism in research. [ 230 ] It is easy to care for in the laboratory and a protocol has been developed which can yield large numbers of embryos on a daily basis. [ 231 ] There is a remarkable degree of similarity in the gene sequence conservation and complexity between the sea anemone and vertebrates. [ 231 ] In particular, genes concerned in the formation of the head in vertebrates are also present in the anemone. [ 232 ] [ 233 ]
Some of the earliest bilaterians were wormlike, and the original bilaterian may have been a bottom dwelling worm with a single body opening. [ 239 ] A bilaterian body can be conceptualized as a cylinder with a gut running between two openings, the mouth and the anus. Around the gut it has an internal body cavity, a coelom or pseudocoelom. [ a ] Animals with this bilaterally symmetric body plan have a head (anterior) end and a tail (posterior) end as well as a back (dorsal) and a belly (ventral); therefore they also have a left side and a right side. [ 240 ] [ 241 ]
Having a front end means that this part of the body encounters stimuli, such as food, favoring cephalisation , the development of a head with sense organs and a mouth. [ 242 ] The body stretches back from the head, and many bilaterians have a combination of circular muscles that constrict the body, making it longer, and an opposing set of longitudinal muscles, that shorten the body; [ 241 ] these enable soft-bodied animals with a hydrostatic skeleton to move by peristalsis . [ 243 ] They also have a gut that extends through the basically cylindrical body from mouth to anus. Many bilaterian phyla have primary larvae which swim with cilia and have an apical organ containing sensory cells. However, there are exceptions to each of these characteristics; for example, adult echinoderms are radially symmetric (unlike their larvae), and certain parasitic worms have extremely simplified body structures. [ 240 ] [ 241 ]
basal bilaterians (lack a true gut) [ 239 ]
develops mouth first →
develops anus first →
Protostomes (from Greek for first mouth ) are a superphylum of animals . It is a sister clade of the deuterostomes (from Greek for second mouth ), with which it forms the Nephrozoa clade. Protostomes are distinguished from deuterostomes by the way their embryos develop . In protostomes the first opening that develops becomes the mouth , while in deuterostomes it becomes the anus. [ 245 ] [ 246 ]
Scalidophora penis worms and mud dragons
arthropods mainly crustaceans
nematodes roundworms
rotifers
arrow worms
flatworms
molluscs gastropods , bivalves and cephalopods
ringed worms
Worms (Old English for serpents ) form a number of phyla. Different groups of marine worms are related only distantly, so they are found in several different phyla such as the Annelida (segmented worms), Chaetognatha (arrow worms), Phoronida (horseshoe worms), and Hemichordata . All worms, apart from the Hemichordata, are protostomes. The Hemichordata are
deuterostomes and are discussed in their own section below.
The typical body plan of a worm involves long cylindrical tube-like bodies and no limbs . Marine worms vary in size from microscopic to over 1 metre (3.3 ft) in length for some marine polychaete worms ( bristle worms ) [ 247 ] and up to 58 metres (190 ft) for the marine nemertean worm ( bootlace worm ). [ 248 ] Some marine worms occupy a small variety of parasitic niches, living inside the bodies of other animals, while others live more freely in the marine environment or by burrowing underground. Many of these worms have specialized tentacles used for exchanging oxygen and carbon dioxide and also may be used for reproduction. Some marine worms are tube worms , such as the giant tube worm which lives in waters near underwater volcanoes and can withstand temperatures up to 90 degrees Celsius . Platyhelminthes (flatworms) form another worm phylum which includes a class of parasitic tapeworms. The marine tapeworm Polygonoporus giganticus , found in the gut of sperm whales , can grow to over 30 m (100 ft). [ 249 ] [ 250 ]
Nematodes (roundworms) constitute a further worm phylum with tubular digestive systems and an opening at both ends. [ 251 ] [ 252 ] Over 25,000 nematode species have been described, [ 253 ] [ 254 ] of which more than half are parasitic. It has been estimated that another million are beyond our current knowledge. [ 255 ] They are ubiquitous in marine, freshwater and terrestrial environments, where they often outnumber other animals in both individual and species counts. They are found in every part of the Earth's lithosphere , from the top of mountains to the bottom of oceanic trenches . [ 256 ] By count they represent 90% of all animals on the ocean floor . [ 257 ] Their numerical dominance, often exceeding a million individuals per square meter and accounting for about 80% of all individual animals on Earth, their diversity of life cycles, and their presence at various trophic levels point at an important role in many ecosystems. [ 258 ]
Molluscs (Latin for soft ) form a phylum with about 85,000 extant recognized species . [ 261 ] They are the largest marine phylum in terms of species count, containing about 23% of all the named marine organisms . [ 262 ] Molluscs have more varied forms than other invertebrate phyla. They are highly diverse, not just in size and in anatomical structure, but also in behavior and in habitat.
The mollusc phylum is divided into 9 or 10 taxonomic classes . These classes include gastropods , bivalves and cephalopods , as well as other lesser-known but distinctive classes. Gastropods with protective shells are referred to as snails , whereas gastropods without protective shells are referred to as slugs . Gastropods are by far the most numerous molluscs in terms of species. [ 263 ] Bivalves include clams , oysters , cockles , mussels , scallops , and numerous other families . There are about 8,000 marine bivalves species (including brackish water and estuarine species). A deep sea ocean quahog clam has been reported as having lived 507 years [ 264 ] making it the longest recorded life of all animals apart from colonial animals, or near-colonial animals like sponges . [ 210 ]
Cephalopods include octopus , squid and cuttlefish . About 800 living species of marine cephalopods have been identified, [ 265 ] and an estimated 11,000 extinct taxa have been described. [ 266 ] They are found in all oceans, but there are no fully freshwater cephalopods. [ 267 ]
Molluscs have such diverse shapes that many textbooks base their descriptions of molluscan anatomy on a generalized or hypothetical ancestral mollusc . This generalized mollusc is unsegmented and bilaterally symmetrical with an underside consisting of a single muscular foot . Beyond that it has three further key features. Firstly, it has a muscular cloak called a mantle covering its viscera and containing a significant cavity used for breathing and excretion . A shell secreted by the mantle covers the upper surface. Secondly (apart from bivalves) it has a rasping tongue called a radula used for feeding. Thirdly, it has a nervous system including a complex digestive system using microscopic, muscle-powered hairs called cilia to exude mucus . The generalized mollusc has two paired nerve cords (three in bivalves). The brain , in species that have one, encircles the esophagus . Most molluscs have eyes and all have sensors detecting chemicals, vibrations, and touch. [ 271 ] [ 272 ]
Good evidence exists for the appearance of marine gastropods, cephalopods and bivalves in the Cambrian period 538.8 to 486.85 million years ago .
Arthropods (Greek for jointed feet ) have an exoskeleton (external skeleton ), a segmented body, and jointed appendages (paired appendages). They form a phylum which includes insects , arachnids , myriapods , and crustaceans . Arthropods are characterized by their jointed limbs and cuticle made of chitin , often mineralized with calcium carbonate . The arthropod body plan consists of segments , each with a pair of appendages . The rigid cuticle inhibits growth, so arthropods replace it periodically by moulting . Their versatility has enabled them to become the most species-rich members of all ecological guilds in most environments.
The evolutionary ancestry of arthropods dates back to the Cambrian period and is generally regarded as monophyletic . However, basal relationships of arthropods with extinct phyla such as lobopodians have recently been debated. [ 275 ] [ 276 ]
tardigrades water bears
velvet worms (terrestrial)
arthropods mainly crustaceans
Extant marine arthropods range in size from the microscopic crustacean Stygotantulus to the Japanese spider crab . Arthropods' primary internal cavity is a hemocoel , which accommodates their internal organs , and through which their haemolymph - analogue of blood - circulates; they have open circulatory systems . Like their exteriors, the internal organs of arthropods are generally built of repeated segments. Their nervous system is "ladder-like", with paired ventral nerve cords running through all segments and forming paired ganglia in each segment. Their heads are formed by fusion of varying numbers of segments, and their brains are formed by fusion of the ganglia of these segments and encircle the esophagus . The respiratory and excretory systems of arthropods vary, depending as much on their environment as on the subphylum to which they belong.
Arthropod vision relies on various combinations of compound eyes and pigment-pit ocelli : in most species the ocelli can only detect the direction from which light is coming, and the compound eyes are the main source of information. Arthropods also have a wide range of chemical and mechanical sensors, mostly based on modifications of the many setae (bristles) that project through their cuticles. Arthropod methods of reproduction are diverse: terrestrial species use some form of internal fertilization while marine species lay eggs using either internal or external fertilization . Arthropod hatchlings vary from miniature adults to grubs that lack jointed limbs and eventually undergo a total metamorphosis to produce the adult form.
In deuterostomes the first opening that develops in the growing embryo becomes the anus , while in protostomes it becomes the mouth. Deuterostomes form a superphylum of animals and are the sister clade of the protostomes . [ 245 ] [ 246 ] It is once considered that the earliest known deuterostomes are Saccorhytus fossils from about 540 million years ago. [ 283 ] However, another study considered that Saccorhytus is more likely to be an ecdysozoan . [ 284 ]
echinoderms
hemichordates
cephalochordates
tunicates
vertebrates →
Echinoderms (Greek for spiny skin ) is a phylum which contains only marine invertebrates. The phylum contains about 7000 living species , [ 285 ] making it the second-largest grouping of deuterostomes , after the chordates .
Adult echinoderms are recognizable by their radial symmetry (usually five-point) and include starfish , sea urchins , sand dollars , and sea cucumbers , as well as the sea lilies . [ 286 ] Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone . They are unique among animals in having bilateral symmetry at the larval stage, but five-fold symmetry ( pentamerism , a special type of radial symmetry) as adults. [ 287 ]
Echinoderms are important both biologically and geologically. Biologically, there are few other groupings so abundant in the biotic desert of the deep sea , as well as shallower oceans. Most echinoderms are able to regenerate tissue, organs, limbs, and reproduce asexually ; in some cases, they can undergo complete regeneration from a single limb. Geologically, the value of echinoderms is in their ossified skeletons , which are major contributors to many limestone formations, and can provide valuable clues as to the geological environment. They were the most used species in regenerative research in the 19th and 20th centuries.
It is held by some scientists that the radiation of echinoderms was responsible for the Mesozoic Marine Revolution . Aside from the hard-to-classify Arkarua (a Precambrian animal with echinoderm-like pentamerous radial symmetry), the first definitive members of the phylum appeared near the start of the Cambrian .
Hemichordates form a sister phylum to the echinoderms . They are solitary worm-shaped organisms rarely seen by humans because of their lifestyle. They include two main groups, the acorn worms and the Pterobranchia . Pterobranchia form a class containing about 30 species of small worm-shaped animals that live in secreted tubes on the ocean floor. Acorn worms form a class containing about 111 species that generally live in U-shaped burrows on the seabed, from the shoreline to a depth of 3000 meters. The worms lie there with the proboscis sticking out of one opening in the burrow, subsisting as deposit feeders or suspension feeders. It is supposed the ancestors of acorn worms used to live in tubes like their relatives, the Pterobranchia, but eventually started to live a safer and more sheltered existence in sediment burrows. [ 292 ] Some of these worms may grow to be very long; one particular species may reach a length of 2.5 meters (8 ft 2 in), although most acorn worms are much smaller.
Acorn worms are more highly specialized and advanced than other worm-like organisms. They have a circulatory system with a heart that also functions as a kidney. Acorn worms have gill-like structures they use for breathing, similar to the gills of fish. Therefore, acorn worms are sometimes said to be a link between classical invertebrates and vertebrates . Acorn worms continually form new gill slits as they grow in size, and some older individuals have more than a hundred on each side. Each slit consists of a branchial chamber opening to the pharynx through a U-shaped cleft. Cilia push water through the slits, maintaining a constant flow, just as in fish. [ 293 ] Some acorn worms also have a postanal tail which may be homologous to the post-anal tail of vertebrates.
The three-section body plan of the acorn worm is no longer present in the vertebrates, except in the anatomy of the frontal neural tube, later developed into a brain divided into three parts. This means some of the original anatomy of the early chordate ancestors is still present in vertebrates even if it is not always visible. One theory is the three-part body originated from an early common ancestor of the deuterostomes, and maybe even from a common bilateral ancestor of both deuterostomes and protostomes. Studies have shown the gene expression in the embryo share three of the same signaling centers that shape the brains of all vertebrates, but instead of taking part in the formation of their neural system, [ 294 ] they are controlling the development of the different body regions. [ 295 ]
The chordate phylum has three subphyla, one of which is the vertebrates (see below). The other two subphyla are marine invertebrates: the tunicates ( salps and sea squirts ) and the cephalochordates (such as lancelets ). Invertebrate chordates are close relatives to vertebrates. In particular, there has been discussion about how closely some extinct marine species, such as Pikaiidae , Palaeospondylus , Zhongxiniscus and Vetulicolia , might relate ancestrally to vertebrates.
Vertebrates (Latin for joints of the spine ) are a subphylum of chordates . They are chordates that have a vertebral column (backbone). The vertebral column provides the central support structure for an internal skeleton which gives shape, support, and protection to the body and can provide a means of anchoring fins or limbs to the body. The vertebral column also serves to house and protect the spinal cord that lies within the vertebral column.
Marine vertebrates can be divided into marine fish and marine tetrapods .
Fish typically breathe by extracting oxygen from water through gills and have a skin protected by scales and mucous . They use fins to propel and stabilise themselves in the water, and usually have a two-chambered heart and eyes well adapted to seeing underwater, as well as other sensory systems . Over 33,000 species of fish have been described as of 2017, [ 300 ] of which about 20,000 are marine fish. [ 301 ]
hagfish
lampreys
cartilaginous fish
bony fish →
Early fish had no jaws . Most went extinct when they were outcompeted by jawed fish (below), but two groups survived: hagfish and lampreys . Hagfish form a class of about 20 species of eel -shaped, slime -producing marine fish. They are the only known living animals that have a skull but no vertebral column . Lampreys form a superclass containing 38 known extant species of jawless fish . [ 302 ] The adult lamprey is characterized by a toothed, funnel-like sucking mouth. Although they are well known for boring into the flesh of other fish to suck their blood , [ 303 ] only 18 species of lampreys are actually parasitic. [ 304 ] Together hagfish and lampreys are the sister group to vertebrates. Living hagfish remain similar to hagfish from around 300 million years ago. [ 305 ] The lampreys are a very ancient lineage of vertebrates, though their exact relationship to hagfishes and jawed vertebrates is still a matter of dispute. [ 306 ] Molecular analysis since 1992 has suggested that hagfish are most closely related to lampreys, [ 307 ] and so also are vertebrates in a monophyletic sense. Others consider them a sister group of vertebrates in the common taxon of craniata. [ 308 ]
The Tully monster is an extinct genus of soft-bodied bilaterians that lived in tropical estuaries about 300 million years ago. Since 2016 there has been controversy over whether this animal was a vertebrate or an invertebrate. [ 309 ] [ 310 ] In 2020 researchers found "strong evidence" that the Tully monster was a vertebrate, and was a jawless fish in the lineage of the lamprey , [ 311 ] [ 312 ] while in 2023 other researchers found 3D fossils scans did not support those conclusions. [ 313 ]
Pteraspidomorphi is an extinct class of early jawless fish ancestral to jawed vertebrates. The few characteristics they share with the latter are now considered as primitive for all vertebrates .
Around the start of the Devonian , fish started appearing with a deep remodelling of the vertebrate skull that resulted in a jaw . [ 314 ] All vertebrate jaws, including the human jaw, have evolved from these early fish jaws. The appearance of the early vertebrate jaw has been described as "perhaps the most profound and radical evolutionary step in vertebrate history". [ 315 ] [ 316 ] Jaws make it possible to capture, hold, and chew prey. Fish without jaws had more difficulty surviving than fish with jaws, and most jawless fish became extinct during the Triassic period.
Jawed fish fall into two main groups: fish with bony internal skeletons and fish with cartilaginous internal skeletons . Cartilaginous fish, such as sharks and rays , have jaws and skeletons made of cartilage rather than bone . Megalodon is an extinct species of shark that lived about 28 to 1.5 Ma. It may looked much like a stocky version of the great white shark , but was much larger with estimated lengths reaching 20.3 metres (67 ft). [ 317 ] Found in all oceans [ 318 ] it was one of the largest and most powerful predators in vertebrate history, [ 317 ] and probably had a profound impact on marine life. [ 319 ] The Greenland shark has the longest known lifespan of all vertebrates, about 400 years. [ 320 ] Some sharks such as the great white are partially warm blooded and give live birth. The manta ray , largest ray in the world, has been targeted by fisheries and is now vulnerable . [ 321 ]
Bony fish have jaws and skeletons made of bone rather than cartilage . Bony fish also have hard, bony plates called operculum which help them respire and protect their gills, and they often possess a swim bladder which they use for better control of their buoyancy. Bony fish can be further divided into those with lobe fins and those with ray fins . The approximate dates in the phylogenetic tree are from Near et al., 2012 [ 323 ] and Zhu et al., 2009. [ 324 ]
coelacanths
lungfish
tetrapods →
( sturgeon , paddlefish , bichir , reedfish )
( bowfin , gars )
all remaining fish (about 14,000 marine species)
Lobe fins have the form of fleshy lobes supported by bony stalks which extend from the body. [ 325 ] Guiyu oneiros , the earliest-known bony fish, lived during the Late Silurian 419 million years ago. It has the combination of both ray-finned and lobe-finned features, although analysis of the totality of its features place it closer to lobe-finned fish. [ 324 ] Lobe fins evolved into the legs of the first tetrapod land vertebrates, so by extension an early ancestor of humans was a lobe-finned fish. Apart from the coelacanths and the lungfishes, lobe-finned fishes are now extinct.
The remaining bony fish have ray fins. These are made of webs of skin supported by bony or horny spines (rays) which can be erected to control the fin stiffness.
About 96% of all modern fish species are teleosts, [ 328 ] of which about 14,000 are marine species. [ 329 ] Teleosts can be distinguished from other bony fish by their possession of a homocercal tail , a tail where the upper half mirrors the lower half. [ 330 ] Another difference lies in their jaw bones – teleosts have modifications in the jaw musculature which make it possible for them to protrude their jaws . This enables them to grab prey and draw it into their mouth . [ 330 ] In general, teleosts tend to be quicker and more flexible than more basal bony fishes. Their skeletal structure has evolved towards greater lightness. While teleost bones are well calcified , they are constructed from a scaffolding of struts, rather than the dense cancellous bones of holostean fish. [ 331 ]
Teleosts are found in almost all marine habitats . [ 332 ] They have enormous diversity , and range in size from adult gobies 8mm long [ 333 ] to ocean sunfish weighing over 2,000 kg. [ 334 ] The following images show something of the diversity in the shape and colour of modern marine teleosts...
Nearly half of all extant vertebrate species are teleosts. [ 335 ]
A tetrapod (Greek for four feet ) is a vertebrate with limbs (feet). Tetrapods evolved from ancient lobe-finned fishes about 400 million years ago during the Devonian Period when their earliest ancestors emerged from the sea and adapted to living on land. [ 336 ] This change from a body plan for breathing and navigating in gravity-neutral water to a body plan with mechanisms enabling the animal to breath in air without dehydrating and move on land is one of the most profound evolutionary changes known. [ 337 ] [ 338 ] Tetrapods can be divided into four classes: amphibians , reptiles , birds and mammals .
amphibians (there are no true marine amphibians)
mammals
lepidosaurs (lizards, including snakes)
archosaurs (turtles, crocodiles & birds)
Marine tetrapods are tetrapods that returned from land back to the sea again. The first returns to the ocean may have occurred as early as the Carboniferous Period [ 339 ] whereas other returns occurred as recently as the Cenozoic , as in cetaceans, pinnipeds , [ 340 ] and several modern amphibians . [ 341 ] Amphibians (from Greek for both kinds of life ) live part of their life in water and part on land. They mostly require fresh water to reproduce. A few inhabit brackish water, but there are no true marine amphibians. [ 342 ] There have been reports, however, of amphibians invading marine waters, such as a Black Sea invasion by the natural hybrid Pelophylax esculentus reported in 2010. [ 343 ]
Reptiles (Late Latin for creeping or crawling ) do not have an aquatic larval stage, and in this way are unlike amphibians. Most reptiles are oviparous, although several species of squamates are viviparous , as were some extinct aquatic clades [ 344 ] — the fetus develops within the mother, contained in a placenta rather than an eggshell . As amniotes , reptile eggs are surrounded by membranes for protection and transport, which adapt them to reproduction on dry land. Many of the viviparous species feed their fetuses through various forms of placenta analogous to those of mammals , with some providing initial care for their hatchlings.
Some reptiles are more closely related to birds than other reptiles, and many scientists prefer to make Reptilia a monophyletic group which includes the birds. [ 345 ] [ 346 ] [ 347 ] [ 348 ] Extant non-avian reptiles which inhabit or frequent the sea include sea turtles , sea snakes , terrapins , the marine iguana , and the saltwater crocodile . Currently, of the approximately 12,000 extant reptile species and sub-species, only about 100 of are classed as marine reptiles. [ 349 ]
Except for some sea snakes, most extant marine reptiles are oviparous and need to return to land to lay their eggs. Apart from sea turtles, the species usually spend most of their lives on or near land rather than in the ocean. Sea snakes generally prefer shallow waters nearby land, around islands, especially waters that are somewhat sheltered, as well as near estuaries. [ 350 ] [ 351 ] Unlike land snakes, sea snakes have evolved flattened tails which help them swim. [ 352 ]
Some extinct marine reptiles, such as ichthyosaurs , evolved to be viviparous and had no requirement to return to land. Ichthyosaurs resembled dolphins. They first appeared about 245 million years ago and disappeared about 90 million years ago. The terrestrial ancestor of the ichthyosaur had no features already on its back or tail that might have helped along the evolutionary process. Yet the ichthyosaur developed a dorsal and tail fin which improved its ability to swim. [ 353 ] The biologist Stephen Jay Gould said the ichthyosaur was his favourite example of convergent evolution . [ 354 ] The earliest marine reptiles arose in the Permian . During the Mesozoic many groups of reptiles became adapted to life in the seas, including ichthyosaurs , plesiosaurs , mosasaurs , nothosaurs , placodonts , sea turtles , thalattosaurs and thalattosuchians . Marine reptiles were less numerous after mass extinction at the end of the Cretaceous .
Marine birds are adapted to life within the marine environment. They are often called seabirds . While marine birds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution , as the same environmental problems and feeding niches have resulted in similar adaptations. Examples include albatross , penguins , gannets , and auks .
In general, marine birds live longer, breed later and have fewer young than terrestrial birds do, but they invest a great deal of time in their young. Most species nest in colonies , which can vary in size from a few dozen birds to millions. Many species are famous for undertaking long annual migrations , crossing the equator or circumnavigating the Earth in some cases. They feed both at the ocean's surface and below it, and even feed on each other. Marine birds can be highly pelagic , coastal, or in some cases spend a part of the year away from the sea entirely. Some marine birds plummet from heights, plunging through the water leaving vapour-like trails, similar to that of fighter planes. [ 355 ] Gannets plunge into the water at up to 100 kilometres per hour (60 mph). They have air sacs under their skin in their face and chest which act like bubble-wrap , cushioning the impact with the water.
The first marine birds evolved in the Cretaceous period , and modern marine bird families emerged in the Paleogene .
Mammals (from Latin for breast ) are characterised by the presence of mammary glands which in females produce milk for feeding (nursing) their young. There are about 130 living and recently extinct marine mammal species such as seals , dolphins , whales , manatees , sea otters and polar bears . [ 356 ] They do not represent a distinct taxon or systematic grouping, but are instead unified by their reliance on the marine environment for feeding. Both cetaceans and sirenians are fully aquatic and therefore are obligate water dwellers. Seals and sea-lions are semiaquatic; they spend the majority of their time in the water, but need to return to land for important activities such as mating , breeding and molting . In contrast, both otters and the polar bear are much less adapted to aquatic living. Their diet varies considerably as well: some may eat zooplankton ; others may eat fish, squid, shellfish, and sea-grass; and a few may eat other mammals.
In a process of convergent evolution , marine mammals, especially cetaceans such as dolphins and whales, redeveloped their body plan to parallel the streamlined fusiform body plan of pelagic fish . Front legs became flippers and back legs disappeared, a dorsal fin reappeared and the tail morphed into a powerful horizontal fluke . This body plan is an adaptation to being an active predator in a high drag environment. A parallel convergence occurred with the now extinct marine reptile ichthyosaur . [ 357 ]
Primary producers are the autotroph organisms that make their own food instead of eating other organisms. This means primary producers become the starting point in the food chain for heterotroph organisms that do eat other organisms. Some marine primary producers are specialised bacteria and archaea which are chemotrophs , making their own food by gathering around hydrothermal vents and cold seeps and using chemosynthesis . However most marine primary production comes from organisms which use photosynthesis on the carbon dioxide dissolved in the water. This process uses energy from sunlight to convert water and carbon dioxide [ 360 ] : 186–187 into sugars that can be used both as a source of chemical energy and of organic molecules that are used in the structural components of cells. [ 360 ] : 1242 Marine primary producers are important because they underpin almost all marine animal life by generating most of the oxygen and food that provide other organisms with the chemical energy they need to exist.
The principal marine primary producers are cyanobacteria , algae and marine plants. The oxygen released as a by-product of photosynthesis is needed by nearly all living things to carry out cellular respiration . In addition, primary producers are influential in the global carbon and water cycles. They stabilize coastal areas and can provide habitats for marine animals. The term division has been traditionally used instead of phylum when discussing primary producers, but the International Code of Nomenclature for algae, fungi, and plants now accepts both terms as equivalents. [ 361 ]
Cyanobacteria were the first organisms to evolve an ability to turn sunlight into chemical energy. They form a phylum (division) of bacteria which range from unicellular to filamentous and include colonial species . They are found almost everywhere on earth: in damp soil, in both freshwater and marine environments, and even on Antarctic rocks. [ 362 ] In particular, some species occur as drifting cells floating in the ocean, and as such were amongst the first of the phytoplankton .
The first primary producers that used photosynthesis were oceanic cyanobacteria about 2.3 billion years ago. [ 363 ] [ 364 ] The release of molecular oxygen by cyanobacteria as a by-product of photosynthesis induced global changes in the Earth's environment. Because oxygen was toxic to most life on Earth at the time, this led to the near-extinction of oxygen-intolerant organisms , a dramatic change which redirected the evolution of the major animal and plant species. [ 365 ]
The tiny marine cyanobacterium Prochlorococcus , discovered in 1986, forms today part of the base of the ocean food chain and accounts for much of the photosynthesis of the open ocean [ 366 ] and an estimated 20% of the oxygen in the Earth's atmosphere. [ 367 ] It is possibly the most plentiful genus on Earth: a single millilitre of surface seawater may contain 100,000 cells or more. [ 368 ]
Originally, biologists classified cyanobacteria as algae, and referred to it as "blue-green algae". The more recent view is that cyanobacteria are bacteria, and hence are not even in the same Kingdom as algae. Most authorities today exclude all prokaryotes , and hence cyanobacteria from the definition of algae. [ 369 ] [ 370 ]
Algae is an informal term for a widespread and diverse group of photosynthetic protists which are not necessarily closely related and are thus polyphyletic . Marine algae can be divided into six groups:
Unlike higher plants, algae lack roots, stems, or leaves. They can be classified by size as microalgae or macroalgae .
Microalgae are the microscopic types of algae, not visible to the naked eye. They are mostly unicellular species which exist as individuals or in chains or groups, though some are multicellular . Microalgae are important components of the marine protists ( discussed above ), as well as the phytoplankton ( discussed below ). They are very diverse . It has been estimated there are 200,000-800,000 species of which about 50,000 species have been described. [ 379 ] Depending on the species, their sizes range from a few micrometers (μm) to a few hundred micrometers. They are specially adapted to an environment dominated by viscous forces.
Macroalgae are the larger, multicellular and more visible types of algae, commonly called seaweeds . Seaweeds usually grow in shallow coastal waters where they are anchored to the seafloor by a holdfast . Seaweed that becomes adrift can wash up on beaches. Kelp is a large brown seaweed that forms large underwater forests covering about 25% of the world coastlines. [ 381 ] They are among the most productive and dynamic ecosystems on Earth. [ 382 ] Some Sargassum seaweeds are planktonic (free-floating). Like microalgae, macroalgae (seaweeds) are technically marine protists since they are not true plants.
Unicellular organisms are usually microscopic, less than one tenth of a millimeter long. There are exceptions. Mermaid's wineglass , a genus of subtropical green algae , is single-celled but remarkably large and complex in form with a single large nucleus, making it a model organism for studying cell biology . [ 385 ] Another single celled algae, Caulerpa taxifolia , has the appearance of a vascular plant including "leaves" arranged neatly up stalks like a fern. Selective breeding in aquariums to produce hardier strains resulted in an accidental release into the Mediterranean where it has become an invasive species known colloquially as killer algae . [ 386 ]
Back in the Silurian , some phytoplankton evolved into red , brown and green algae . These algae then invaded the land and started evolving into the land plants we know today. Later, in the Cretaceous , some of these land plants returned to the sea as marine plants, such as mangroves and seagrasses . [ 387 ]
Marine plants can be found in intertidal zones and shallow waters, such as seagrasses like eelgrass and turtle grass , Thalassia . These plants have adapted to the high salinity of the ocean environment. Plant life can also flourish in the brackish waters of estuaries , where mangroves or cordgrass or beach grass beach grass might grow.
The total world area of mangrove forests was estimated in 2010 as 134,257 square kilometres (51,837 sq mi) (based on satellite data). [ 389 ] [ 390 ] The total world area of seagrass meadows is more difficult to determine, but was conservatively estimated in 2003 as 177,000 square kilometres (68,000 sq mi). [ 391 ]
Mangroves and seagrasses provide important nursery habitats for marine life, acting as hiding and foraging places for larval and juvenile forms of larger fish and invertebrates. [ 392 ]
Plankton (from Greek for wanderers ) are a diverse group of organisms that live in the water column of large bodies of water but cannot swim against a current. As a result, they wander or drift with the currents. [ 393 ] Plankton are defined by their ecological niche , not by any phylogenetic or taxonomic classification. They are a crucial source of food for many marine animals, from forage fish to whales . Plankton can be divided into a plant-like component and an animal component.
Phytoplankton are the plant-like components of the plankton community ("phyto" comes from the Greek for plant ). They are autotrophic (self-feeding), meaning they generate their own food and do not need to consume other organisms.
Phytoplankton consist mainly of microscopic photosynthetic eukaryotes which inhabit the upper sunlit layer in all oceans. They need sunlight so they can photosynthesize. Most phytoplankton are single-celled algae, but other phytoplankton are bacteria and some are protists . [ 394 ] Phytoplankton groups include cyanobacteria (above) , diatoms , various other types of algae (red, green, brown, and yellow-green), dinoflagellates , euglenoids , coccolithophorids , cryptomonads , chrysophytes , chlorophytes , prasinophytes , and silicoflagellates . They form the base of the primary production that drives the ocean food web , and account for half of the current global primary production, more than the terrestrial forests. [ 395 ]
Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek for animal ). They are heterotrophic (other-feeding), meaning they cannot produce their own food and must consume instead other plants or animals as food. In particular, this means they eat phytoplankton.
Zooplankton are generally larger than phytoplankton, mostly still microscopic but some can be seen with the naked eye. Many protozoans (single-celled protists that prey on other microscopic life) are zooplankton, including zooflagellates , foraminiferans , radiolarians and some dinoflagellates . Other dinoflagellates are mixotrophic and could also be classified as phytoplankton; the distinction between plants and animals often breaks down in very small organisms. Other zooplankton include pelagic cnidarians , ctenophores , molluscs , arthropods and tunicates , as well as planktonic arrow worms and bristle worms .
Radiolarians are unicellular protists with elaborate silica shells
Microzooplankton: major grazers of the plankton
Larger zooplankton can be predatory on smaller zooplankton.
Macrozooplankton
Many marine animals begin life as zooplankton in the form of eggs or larvae, before they develop into adults. These are meroplanktic , that is, they are planktonic for only part of their life.
Dinoflagellates are often mixotrophic or live in symbiosis with other organisms.
Some dinoflagellates are bioluminescent . At night, ocean water can light up internally and sparkle with blue light because of these dinoflagellates. [ 400 ] [ 401 ] Bioluminescent dinoflagellates possess scintillons , individual cytoplasmic bodies which contain dinoflagellate luciferase , the main enzyme involved in the luminescence. The luminescence, sometimes called the phosphorescence of the sea , occurs as brief (0.1 sec) blue flashes or sparks when individual scintillons are stimulated, usually by mechanical disturbances from, for example, a boat or a swimmer or surf. [ 402 ]
Compared to terrestrial environments, marine environments have biomass pyramids which are inverted at the base. In particular, the biomass of consumers (copepods, krill, shrimp, forage fish) is larger than the biomass of primary producers. This happens because the ocean's primary producers are tiny phytoplankton which tend to be r-strategists that grow and reproduce rapidly, so a small mass can have a fast rate of primary production. In contrast, terrestrial primary producers, such as mature forests, are often K-strategists that grow and reproduce slowly, so a much larger mass is needed to achieve the same rate of primary production.
Because of this inversion, it is the zooplankton that make up most of the marine animal biomass . As primary consumers , they are the crucial link between the primary producers (mainly phytoplankton) and the rest of the marine food web ( secondary consumers ). [ 403 ]
If phytoplankton dies before it is eaten, it descends through the euphotic zone as part of the marine snow and settles into the depths of sea. In this way, phytoplankton sequester about 2 billion tons of carbon dioxide into the ocean each year, causing the ocean to become a sink of carbon dioxide holding about 90% of all sequestered carbon. [ 404 ]
In 2010 researchers found whales carry nutrients from the depths of the ocean back to the surface using a process they called the whale pump . [ 405 ] Whales feed at deeper levels in the ocean where krill is found, but return regularly to the surface to breathe. There whales defecate a liquid rich in nitrogen and iron. Instead of sinking, the liquid stays at the surface where phytoplankton consume it. In the Gulf of Maine the whale pump provides more nitrogen than the rivers. [ 406 ]
Taken as a whole, the oceans form a single marine system where water – the "universal solvent" [ 407 ] – dissolves nutrients and substances containing elements such as oxygen, carbon, nitrogen and phosphorus. These substances are endlessly cycled and recycled, chemically combined and then broken down again, dissolved and then precipitated or evaporated, imported from and exported back to the land and the atmosphere and the ocean floor. Powered both by the biological activity of marine organisms and by the natural actions of the sun and tides and movements within the Earth's crust, these are the marine biogeochemical cycles . [ 408 ] [ 409 ]
Sediments at the bottom of the ocean have two main origins, terrigenous and biogenous. Terrigenous sediments account for about 45% of the total marine sediment, and originate in the erosion of rocks on land, transported by rivers and land runoff, windborne dust, volcanoes, or grinding by glaciers.
Biogenous sediments account for the other 55% of the total sediment, and originate in the skeletal remains of marine protists (single-celled plankton and benthos organisms). Much smaller amounts of precipitated minerals and meteoric dust can also be present. Ooze , in the context of a marine sediment, does not refer to the consistency of the sediment but to its biological origin. The term ooze was originally used by John Murray , the "father of modern oceanography", who proposed the term radiolarian ooze for the silica deposits of radiolarian shells brought to the surface during the Challenger Expedition . [ 411 ] A biogenic ooze is a pelagic sediment containing at least 30 percent from the skeletal remains of marine organisms.
Land interactions impact marine life in many ways. Coastlines typically have continental shelves extending some way from the shore. These provide extensive shallows sunlit down to the seafloor, allowing for photosynthesis and enabling habitats for seagrass meadows, coral reefs, kelp forests and other benthic life . Further from shore the continental shelf slopes towards deep water. Wind blowing at the ocean surface or deep ocean currents can result in cold and nutrient rich waters from abyssal depths moving up the continental slopes . This can result in upwellings along the outer edges of continental shelves, providing conditions for phytoplankton blooms .
Water evaporated by the sun from the surface of the ocean can precipitate on land and eventually return to the ocean as runoff or discharge from rivers, enriched with nutrients as well as pollutants . As rivers discharge into estuaries , freshwater mixes with saltwater and becomes brackish . This provides another shallow water habitat where mangrove forests and estuarine fish thrive. Overall, life in inland lakes can evolve with greater diversity than happens in the sea, because freshwater habitats are themselves diverse and compartmentalised in a way marine habitats are not. Some aquatic life, such as salmon and eels , migrate back and forth between freshwater and marine habitats. These migrations can result in exchanges of pathogens and have impacts on the way life evolves in the ocean.
Human activities affect marine life and marine habitats through overfishing , pollution , acidification and the introduction of invasive species . These impact marine ecosystems and food webs and may result in consequences as yet unrecognised for the biodiversity and continuation of marine life forms. [ 417 ]
Biodiversity is the result of over three billion years of evolution . Until approximately 600 million years ago, all life consisted of archaea , bacteria , protozoans and similar single-celled organisms . The history of biodiversity during the Phanerozoic (the last 540 million years), starts with rapid growth during the Cambrian explosion – a period during which nearly every phylum of multicellular organisms first appeared. Over the next 400 million years or so, invertebrate diversity showed little overall trend and vertebrate diversity shows an overall exponential trend. [ 419 ]
However, more than 99 percent of all species that ever lived on Earth, amounting to over five billion species, [ 420 ] are estimated to be extinct . [ 421 ] [ 422 ] These extinctions occur at an uneven rate. The dramatic rise in diversity has been marked by periodic, massive losses of diversity classified as mass extinction events . [ 419 ] Mass extinction events occur when life undergoes precipitous global declines. Most diversity and biomass on earth is found among the microorganisms , which are difficult to measure. Recorded extinction events are therefore based on the more easily observed changes in the diversity and abundance of larger multicellular organisms , rather than the total diversity and abundance of life. [ 423 ] Marine fossils are mostly used to measure extinction rates because of their superior fossil record and stratigraphic range compared to land organisms.
Based on the fossil record , the background rate of extinctions on Earth is about two to five taxonomic families of marine animals every million years. The Great Oxygenation Event was perhaps the first major extinction event. Since the Cambrian explosion five major mass extinctions have significantly exceeded the background extinction rate. [ 424 ] The worst was the Permian-Triassic extinction event , 251 million years ago. One generally estimates that the Big Five mass extinctions of the Phanerozoic (the last 540 million years) wiped out more than 40% of marine genera and probably more than 70% of marine species. [ 425 ] The current Holocene extinction caused by human activity, and now referred to as the "sixth extinction", may prove ultimately more devastating.
In order to perform research and enrich Marine Life knowledge, Scientists use various methods in-order to reach and explore the depths of the ocean. several Hi-tech instruments and vehicles are used for this purpose. [ 426 ] | https://en.wikipedia.org/wiki/Marine_life |
A marine loading arm , also known as a mechanical loading arm , loading arm , or MLA is a mechanical arm consisting of articulated steel pipes that connect a tankship such as an oil tanker or chemical tanker to a cargo terminal. Genericized trademarks such as Chiksan (often misspelled Chicksan ) are often used to refer to marine loading arms. [ 2 ] [ 3 ]
A marine loading arm is an alternative to direct hose hookups that is particularly useful for larger vessels and transfers at higher loading rates and pressures. [ 2 ] Controlled manually or hydraulically, a loading arm employs swivel joints and can, to some extent, follow the movement of a moored vessel. [ 2 ] [ 4 ] Many loading arm systems feature quick-connect fittings. [ 2 ] Gasket or o-ring arrangements are required to make a secure seal to the ship's manifold flange. [ 2 ] A loading arm must be drained or closed off before the connection is broken off. [ 5 ] This is usually done in two ways. For fuels such as gas oil and diesel, the lines can be blown out with high pressure air. In the case of fuels such as kerosene or petrol, the lines can be stripped with pumps.
Loading arms can handle both liquids and gases, in a wide range of viscosities and temperatures. [ 6 ] Cargoes from liquid sulphur to liquefied natural gas are moved through marine loading arms. [ 6 ] Loading arms service vessels in a wide range of sizes, from small river barges to the largest supertankers . [ 6 ]
Various designs exist, and specific installations can be tailored for a given port based on considerations such as vessel size, cargo flow rate and cargo temperature. [ 6 ] Environmental constraints, such as the range of tide, wind conditions, and earthquake tolerance, can also affect choice of loading arm. [ 6 ] A loading arm installation may include add-ons such as hydraulic or manual quick connect couplers, position monitoring systems, emergency release systems, and piggyback vapor return lines. [ 6 ]
Compared to cargo hoses, the loading arm's main drawback is its comparative lack of flexibility. [ 2 ]
Since the earliest days of tankships, the need to safely and efficiently transfer bulk liquid to a moored ship has been fundamental. An insufficient solution to this problem led to one of the world's first oil tanker disasters. [ 7 ] In 1881, the Branobel tanker Nordenskjöld was taking on kerosene in Baku . [ 7 ] The ship was connected to the pier with a simple piece of pipe. [ 7 ] While loading, the ship was hit by a gust of wind and the cargo pipe carrying was jerked away from the hold. [ 7 ] Kerosene then spilled onto the deck and down into the engine room, where mechanics were working in the light of kerosene lanterns. [ 7 ] The ship then exploded, killing half the crew. [ 7 ] Ludvig Nobel responded to the disaster by creating a flexible, leakproof loading pipe which was much more resistant to spills. [ 8 ]
Chiksan brand marine loading arm manufacturer FMC Technologies claims to have built the world's first all-steel marine loading arm in 1956 and to have over 8,000 units installed worldwide. [ 9 ] | https://en.wikipedia.org/wiki/Marine_loading_arm |
Microbial symbiosis in marine animals was not discovered until 1981. [ 3 ] In the time following, symbiotic relationships between marine invertebrates and chemoautotrophic bacteria have been found in a variety of ecosystems, ranging from shallow coastal waters to deep-sea hydrothermal vents . Symbiosis is a way for marine organisms to find creative ways to survive in a very dynamic environment. They are different in relation to how dependent the organisms are on each other or how they are associated. It is also considered a selective force behind evolution in some scientific aspects. The symbiotic relationships of organisms has the ability to change behavior, morphology and metabolic pathways. With increased recognition and research, new terminology also arises, such as holobiont, which the relationship between a host and its symbionts as one grouping. [ 4 ] Many scientists will look at the hologenome, which is the combined genetic information of the host and its symbionts. These terms are more commonly used to describe microbial symbionts.
The type of marine animal vary greatly, for example, sponges, sea squirts, corals, worms, and algae all host a variety of unique symbionts. [ 5 ] Each symbiotic relationship displays a unique ecological niche, which in turn can lead to entirely new species of host species and symbiont. [ 3 ]
It is particularly interesting that it took so long to discover the marine microbial symbiosis because nearly every surface submerged in the oceans becomes covered with biofilm , [ 6 ] including a large number of living organisms. Many marine organisms display symbiotic relationships with microbes. Epibiotic bacteria have been found to live on crustacean larvae and protect them from fungal infections. [ 6 ] Other microbes in deep-sea vents have been found to prevent the settlement of barnacles and tunicate larvae. [ 6 ]
Various mechanisms are utilized in order to facilitate symbiotic relationships and to help these associates evolve alongside one another. By using horizontal gene transfer, certain genetic elements are able to pass from one organisms to another. In non-mating species, this helps with genetic differentiation and adaptive evolution. [ 7 ] An example of this is the sponge Astroclera willeyana which has a gene that is used in expressing spherulite-forming cells which has an origin in bacteria. Another example is the starlet sea anemone, Nematostella vectensis, which has genes from bacteria that have a role in producing UV radiation protection in the form of shikimic acid. Another way for symbiotic relationships to co-evolve is through genome erosion. This is a process where genes that are typically used during free-living periods aren't necessary because of the symbioses of the organisms. Without that gene, the organism is able to decrease the energy necessary for cell maintenance and replication. [ 7 ]
There are a variety of symbiotic relationships:
The relationship can be either an ectosymbiont , a symbiont that survives by being attached to the surface of the host, which includes areas such as the inner surfaces of the gut cavity, or even the ducts of endocrine glands; or an endosymbiont , a symbiont that lives within its host and can be known as an intracellular symbiont . [ 7 ]
They are further classified by their dependence on their host and can be a facultative symbiont that can exist in a free living condition and is not dependent on its host, or an obligate symbiont , which has adapted in such a way that it is not able to exit without the benefit it receives from its host. An example of an obligate symbioses is the relationship between microalgae and corals. The microalgae provides a large source of the coral diet [ 7 ]
The most notable display of marine symbiotic relationship would be coral. Coral reefs are home to a variety of dinoflagellate symbiont, [ 10 ] these symbionts give coral its bright coloring and are vital for the survival of the reef. The symbionts provide the coral with food in exchange for protection. If the waters warm or become too acidic, the symbionts are expelled, the coral bleaches and if conditions persist the coral will die. This in turn leads to the collapse of the entire reef ecosystem [ 10 ]
Osedax , also called the bone eating worm is a siboglinid worm from polychaete genus. It was discovered in a whalefall community on the surface of bones, in the axis of Monterey Canyon, California, in 2002. Osedax lacks a mouth, a functional gut and a trophosome. But female osedax have a vascularized root system originating from their ovisac which contains heterotrophic endosymbiotic bacterial community dominated by γ-proteobacteria clade. They use the vascularized root system to access the whale bones. The endosymbionts help the host utilize nutrients from the whale bones. [ 11 ]
Hawaiian sepiolid squid Euprymna scolopes and bacterium Vibrio fischeri also show symbiosis. In this symbiosis, symbiont not only serve the host for defense, but also shapes the host morphology. Bioluminescent V. fischeri can be found in epithelial lined crypts of the light organ of the host. Symbiosis begins as soon as a newly hatched squid finds and houses V. fischeri bacteria.
The symbiosis process begins when Peptidoglycan shed by the sea water bacteria comes in contact to the ciliated epithelial cells of the light organ. It induces mucus production in the cells. Mucus entraps bacterial cells. Antimicrobial peptides, nitric oxide and sialyted mucins in the mucus then selectively allow only V. fischeri which encode gene rscS to adhere and win over gram positive and other gram negative bacteria. The symbiotic bacteria are then guided up to the light organ via chemotaxis. After successful colonization, symbionts induce loss of mucus and ciliated sites to prevent further attachment of bacterial cells via MAMP (microbe associated molecular pattern) signalling. Also, they induce changes in protein expression in the host symbiotic tissues and modify both physiology and morphology of light organs. After bacterial cells divide and increase in population, they begin expressing enzyme luciferase as a result of quorum sensing. Luciferase enzymes produce bioluminescence. [ 12 ] Squids can then emit the luminescence from the light organ. Because Euprymna scolopes emerges only during night time, it helps them avoid predation. Bioluminescence allows them to camouflage with the light coming from moon and stars to ocean and avoid predators. [ 13 ]
Alvinella pompejana, the Pompeii worm is a polychaete, found in the far depths of the sea, typically found near hydrothermal vents. They were originally discovered by French researchers in the early 1980s. [ 14 ] They can grow as large as 5 inches long and are normally described as having pale gray coloring with red "tentacle-like" gills protruding from their heads. Their tails are most likely found in temperatures as high as 176 degrees Fahrenheit, while their heads, which stick out from the tubes they live in are only exposed to temperatures as high as 72 degrees Fahrenheit. [ 14 ] Its ability to survive the temperatures of hydrothermal vents lies in its symbiotic relationship with the bacteria that resides on its back. It forms a "fleece-like" protective covering. Mucus is secreted from glands on the back of the Pompeii worm in order to provide nutrients for the bacteria. Further study of the bacteria led to the discovery that they are chemolithotrophic. [ 14 ]
Elysia rufescens grazes on Bryopsis sp., an alga that defends itself from predators by using peptide toxins with fatty acids, called kahalalides. [ 15 ] A bacterial obligate symbiont produces many defensive molecules, including kahalalides, in order to protect the alga. This bacteria is able to use substrates derived from the host in order to synthesize the toxins. [ 15 ] The Hawaiian Sea Slug grazes on the alga in order to accumulate kahalalide. This uptake of the toxin, which the slug is immune to, allows it to also become toxic to predators. This shared ability, both originating from the bacteria, provide protection within the marine ecosystems.
Besides a one to one symbiotic relationship, it is possible for a host to become symbiotic with a microbial consortia. In the case of the sponge (phylum Porifera), they are able to host a lot of wide range of microbial communities that can also be very specific. The microbial communities that form a symbiotic relationship with the sponge can actually comprise up to 35% of the biomass of its host. [ 17 ] The term for this specific symbiotic relationship, where a microbial consortia pairs with a host is called a holobiotic relationship. The sponge as well as the microbial community associated with it will produce a large range of secondary metabolites that help protect it against predators through mechanisms such as chemical defense. [ 18 ] Some of these relationships include endosymbionts within bacteriocyte cells, and cyanobacteria or microalgae found below the pinacoderm cell layer where they are able to receive the highest amount of light, used for phototrophy. They can host approximately 52 different microbial phyla and candidate phyla, including Alphaproteobacteria, Actinobacteria, Chloroflexi, Nitrospirae, Cyanobacteria, the taxa Gamma-, and the candidate phylum Poribacteria, and Thaumarchaea . [ 18 ]
This type of bacteria was first described in 2007. [ 19 ] It is able to form symbiotic relationships with a wide range of hosts in the marine environment such as cnidarians, poriferans, molluscs, annelids, tunicates, and fish. They are distributed through various marine zones from extreme depths to warm photic zones. Endozoicomonas is thought to acquisition nutrients from nitrogen/carbon recycling, methane/sulfur recycling, and synthesize amino acids and various other molecules necessary for life. [ 19 ] It was also found that it has a correlation to photosymbionts which provide carbon and sulfur to the bacteria from dimethylsulfopropionate (DMSP). They are also suspected to help regulate bacterial colonization of the host by using bioactive secondary metabolites or even probiotic mechanisms like limiting pathogenic bacteria by means of competitive exclusion. When Endozoicomonas is removed from the host, there are often signs of lesions on corals and disease. [ 19 ]
Marine environment consists of a large number of chemosynthetic symbioses in different regions of the ocean: shallow-water coastal sediments, continental slope sediments, whale and wood falls, cold seeps and deep-sea hydrothermal vents. Organisms from seven phyla (ciliophora, porifera, platyhelminthes, nematoda, mollusca, annelida and arthropoda) are known to have chemosynthetic symbiosis till now. Some of them include nematode, tube worms, clam, sponge, hydrothermal vent shrimp, worms mollusc, mussels and so on. The symbionts can be ectosymbionts or endosymbionts . Some ectosymbionts are: symbionts of polychaete worm Alvinella which occur in their dorsal surface and symbionts occurring on the mouthparts and gill chamber of the vent shrimp Rimicaris. Endosymbionts include symbionts of gastropod snails which occur in their gill tissues. In the siboglinid tube worms of the groups Monilifera, Frenulata and Vestimentifera, symbionts can be found in an interior organ called trophosome . [ 20 ]
Most of the animals in deep-sea hydrothermal vents exist in a symbiotic relationship with chemosynthetic bacteria. These chemosynthetic bacteria are found to be methane or sulphur oxidizers. [ 21 ]
Marine invertebrates are the hosts of a wide spectrum of bioactive metabolites, which have vast potential as drugs and research tools. [ 22 ] In many cases, microbes aid in or are responsible for marine invertebrates natural products. [ 22 ] Certain marine microbes can provide insight into the biosynthesis mechanisms of natural products, which in turn could solve the current limitations on marine drug development. [ 5 ] | https://en.wikipedia.org/wiki/Marine_microbial_symbiosis |
Marine microorganisms are defined by their habitat as microorganisms living in a marine environment , that is, in the saltwater of a sea or ocean or the brackish water of a coastal estuary . A microorganism (or microbe ) is any microscopic living organism or virus , which is invisibly small to the unaided human eye without magnification . Microorganisms are very diverse. They can be single-celled [ 1 ] or multicellular and include bacteria , archaea , viruses, and most protozoa , as well as some fungi , algae , and animals, such as rotifers and copepods . Many macroscopic animals and plants have microscopic juvenile stages . Some microbiologists also classify viruses as microorganisms, but others consider these as non-living. [ 2 ] [ 3 ]
Marine microorganisms have been variously estimated to make up about 70%, [ 4 ] or about 90%, [ 5 ] [ 6 ] of the biomass in the ocean . Taken together they form the marine microbiome . Over billions of years this microbiome has evolved many life styles and adaptations and come to participate in the global cycling of almost all chemical elements. [ 7 ] Microorganisms are crucial to nutrient recycling in ecosystems as they act as decomposers . They are also responsible for nearly all photosynthesis that occurs in the ocean, as well as the cycling of carbon , nitrogen , phosphorus and other nutrients and trace elements. [ 8 ] Marine microorganisms sequester large amounts of carbon and produce much of the world's oxygen.
A small proportion of marine microorganisms are pathogenic , causing disease and even death in marine plants and animals. [ 9 ] However marine microorganisms recycle the major chemical elements , both producing and consuming about half of all organic matter generated on the planet every year. As inhabitants of the largest environment on Earth, microbial marine systems drive changes in every global system.
In July 2016, scientists reported identifying a set of 355 genes from the last universal common ancestor (LUCA) of all life on the planet, including the marine microorganisms. [ 10 ] Despite its diversity, microscopic life in the oceans is still poorly understood. For example, the role of viruses in marine ecosystems has barely been explored even in the beginning of the 21st century. [ 11 ]
Microorganisms make up about 70% of the marine biomass . [ 4 ] A microorganism , or microbe, is a microscopic organism too small to be recognised adequately with the naked eye. In practice, that includes organisms smaller than about 0.1 mm. [ 12 ] : 13
Such organisms can be single-celled [ 1 ] or multicellular . Microorganisms are diverse and include all bacteria and archaea , most protists including algae , protozoa and fungal-like protists, as well as certain microscopic animals such as rotifers . Many macroscopic animals and plants have microscopic juvenile stages . Some microbiologists also classify viruses as microorganisms, but others consider these as non-living. [ 2 ] [ 3 ]
Microorganisms are crucial to nutrient recycling in ecosystems as they act as decomposers . Some microorganisms are pathogenic , causing disease and even death in plants and animals. [ 9 ] As inhabitants of the largest environment on Earth, microbial marine systems drive changes in every global system. Microbes are responsible for virtually all the photosynthesis that occurs in the ocean, as well as the cycling of carbon , nitrogen , phosphorus and other nutrients and trace elements. [ 8 ]
Viruses
Bacteria
Archaea
Protists
Microfungi
Microanimals
While recent technological developments and scientific discoveries have been substantial, we still lack a major understanding at all levels of the basic ecological questions in relation to the microorganisms in our seas and oceans. These fundamental questions are: 1. What is out there? Which microorganisms are present in our seas and oceans and in what numbers
do they occur? 2. What are they doing? What functions do each of these microorganisms perform in the marine environment and how do they contribute to the global cycles of energy and matter? 3. What are the factors that determine the presence or absence of a microorganism and how do they influence biodiversity and function and vice versa?
Microscopic life undersea is diverse and still poorly understood, such as for the role of viruses in marine ecosystems. [ 13 ] Most marine viruses are bacteriophages , which are harmless to plants and animals, but are essential to the regulation of saltwater and freshwater ecosystems. [ 14 ] They infect and destroy bacteria in aquatic microbial communities, and are the most important mechanism of recycling carbon in the marine environment. The organic molecules released from the dead bacterial cells stimulate fresh bacterial and algal growth. [ 15 ] Viral activity may also contribute to the biological pump , the process whereby carbon is sequestered in the deep ocean. [ 16 ]
A stream of airborne microorganisms circles the planet above weather systems but below commercial air lanes. [ 17 ] Some peripatetic microorganisms are swept up from terrestrial dust storms, but most originate from marine microorganisms in sea spray . In 2018, scientists reported that hundreds of millions of viruses and tens of millions of bacteria are deposited daily on every square meter around the planet. [ 18 ] [ 19 ]
Microscopic organisms live throughout the biosphere . The mass of prokaryote microorganisms — which includes bacteria and archaea, but not the nucleated eukaryote microorganisms — may be as much as 0.8 trillion tons of carbon (of the total biosphere mass , estimated at between 1 and 4 trillion tons). [ 20 ] Single-celled barophilic marine microbes have been found at a depth of 10,900 m (35,800 ft) in the Mariana Trench , the deepest spot in the Earth's oceans. [ 21 ] [ 22 ] Microorganisms live inside rocks 580 m (1,900 ft) below the sea floor under 2,590 m (8,500 ft) of ocean off the coast of the northwestern United States , [ 21 ] [ 23 ] as well as 2,400 m (7,900 ft; 1.5 mi) beneath the seabed off Japan. [ 24 ] The greatest known temperature at which microbial life can exist is 122 °C (252 °F) ( Methanopyrus kandleri ). [ 25 ] In 2014, scientists confirmed the existence of microorganisms living 800 m (2,600 ft) below the ice of Antarctica . [ 26 ] [ 27 ] According to one researcher, "You can find microbes everywhere — they're extremely adaptable to conditions, and survive wherever they are." [ 21 ] Marine microorganisms serve as "the foundation of all marine food webs, recycling major elements and producing and consuming about half the organic matter generated on Earth each year". [ 28 ] [ 29 ]
A virus is a small infectious agent that replicates only inside the living cells of other organisms . Viruses can infect all types of life forms , from animals and plants to microorganisms , including bacteria and archaea . [ 31 ]
When not inside an infected cell or in the process of infecting a cell, viruses exist in the form of independent particles. These viral particles, also known as virions , consist of two or three parts: (i) the genetic material (genome) made from either DNA or RNA , long molecules that carry genetic information; (ii) a protein coat called the capsid , which surrounds and protects the genetic material; and in some cases (iii) an envelope of lipids that surrounds the protein coat when they are outside a cell. The shapes of these virus particles range from simple helical and icosahedral forms for some virus species to more complex structures for others. Most virus species have virions that are too small to be seen with an optical microscope . The average virion is about one one-hundredth the size of the average bacterium .
The origins of viruses in the evolutionary history of life are unclear: some may have evolved from plasmids —pieces of DNA that can move between cells—while others may have evolved from bacteria. In evolution, viruses are an important means of horizontal gene transfer , which increases genetic diversity . [ 32 ] Viruses are considered by some to be a life form, because they carry genetic material, reproduce, and evolve through natural selection . However, they lack key characteristics (such as cell structure) that are generally considered necessary to count as life. Because they possess some but not all such qualities, viruses have been described as "organisms at the edge of life" [ 33 ] and as replicators. [ 34 ]
Viruses are found wherever there is life and have probably existed since living cells first evolved. [ 35 ] The origin of viruses is unclear because they do not form fossils, so molecular techniques have been used to compare the DNA or RNA of viruses and are a useful means of investigating how they arose. [ 36 ]
Viruses are now recognised as ancient and as having origins that pre-date the divergence of life into the three domains . [ 37 ]
Opinions differ on whether viruses are a form of life or organic structures that interact with living organisms. [ 34 ] They are considered by some to be a life form, because they carry genetic material, reproduce by creating multiple copies of themselves through self-assembly, and evolve through natural selection . However they lack key characteristics such as a cellular structure generally considered necessary to count as life. Because they possess some but not all such qualities, viruses have been described as replicators [ 34 ] and as "organisms at the edge of life". [ 33 ]
Bacteriophages , often just called phages , are viruses that parasite bacteria and archaea. Marine phages parasite marine bacteria and archaea, such as cyanobacteria . [ 38 ] They are a common and diverse group of viruses and are the most abundant biological entity in marine environments, because their hosts, bacteria, are typically the numerically dominant cellular life in the sea. Generally there are about 1 million to 10 million viruses in each mL of seawater, or about ten times more double-stranded DNA viruses than there are cellular organisms, [ 39 ] [ 40 ] although estimates of viral abundance in seawater can vary over a wide range. [ 41 ] [ 42 ] For a long time, tailed phages of the order Caudovirales seemed to dominate marine ecosystems in number and diversity of organisms. [ 38 ] However, as a result of more recent research, non-tailed viruses appear to be dominant in multiple depths and oceanic regions, followed by the Caudovirales families of myoviruses, podoviruses, and siphoviruses. [ 43 ] Phages belonging to the families: Corticoviridae , [ 44 ] Inoviridae , [ 45 ] Microviridae , [ 46 ] and Autolykiviridae [ 47 ] [ 48 ] [ 49 ] [ 50 ] are also known to infect diverse marine bacteria.
There are also archaean viruses which replicate within archaea : these are double-stranded DNA viruses with unusual and sometimes unique shapes. [ 51 ] [ 52 ] These viruses have been studied in most detail in the thermophilic archaea, particularly the orders Sulfolobales and Thermoproteales . [ 53 ]
Microorganisms make up about 70% of the marine biomass. [ 4 ] It is estimated viruses kill 20% of this biomass each day and that there are 15 times as many viruses in the oceans as there are bacteria and archaea. Viruses are the main agents responsible for the rapid destruction of harmful algal blooms , [ 40 ] which often kill other marine life. [ 54 ] The number of viruses in the oceans decreases further offshore and deeper into the water, where there are fewer host organisms. [ 16 ]
Viruses are an important natural means of transferring genes between different species, which increases genetic diversity and drives evolution. [ 32 ] It is thought that viruses played a central role in the early evolution, before the diversification of bacteria, archaea and eukaryotes, at the time of the last universal common ancestor of life on Earth. [ 55 ] Viruses are still one of the largest reservoirs of unexplored genetic diversity on Earth. [ 16 ]
Viruses normally range in length from about 20 to 300 nanometers. This can be contrasted with the length of bacteria, which starts at about 400 nanometers. There are also giant viruses , often called giruses , typically about 1000 nanometers (one micron) in length.
All giant viruses belongto phylum Nucleocytoviricota (NCLDV), together with poxviruses .
The largest known of these is Tupanvirus . This genus of giant virus was discovered in 2018 in the deep ocean as well as a soda lake, and can reach up to 2.3 microns in total length. [ 56 ]
The discovery and subsequent characterization of giant viruses has triggered some debate concerning their evolutionary origins. [ 57 ] The two main hypotheses for their origin are that either they evolved from small viruses, picking up DNA from host organisms, or that they evolved from very complicated organisms into the current form which is not self-sufficient for reproduction. [ 58 ] What sort of complicated organism giant viruses might have diverged from is also a topic of debate. One proposal is that the origin point actually represents a fourth domain of life, [ 59 ] [ 60 ] but this has been largely discounted. [ 61 ] [ 62 ]
Bacteria constitute a large domain of prokaryotic microorganisms . Typically a few micrometres in length, bacteria have a number of shapes, ranging from spheres to rods and spirals. Bacteria were among the first life forms to appear on Earth , and are present in most of its habitats . Bacteria inhabit soil, water, acidic hot springs , radioactive waste , [ 63 ] and the deep portions of Earth's crust . Bacteria also live in symbiotic and parasitic relationships with plants and animals.
Once regarded as plants constituting the class Schizomycetes , bacteria are now classified as prokaryotes . Unlike cells of animals and other eukaryotes , bacterial cells do not contain a nucleus and rarely harbour membrane-bound organelles . Although the term bacteria traditionally included all prokaryotes, the scientific classification changed after the discovery in the 1990s that prokaryotes consist of two very different groups of organisms that evolved from an ancient common ancestor. These evolutionary domains are called Bacteria and Archaea . [ 64 ]
The ancestors of modern bacteria were unicellular microorganisms that were the first forms of life to appear on Earth, about 4 billion years ago. For about 3 billion years, most organisms were microscopic, and bacteria and archaea were the dominant forms of life. [ 65 ] [ 66 ] Although bacterial fossils exist, such as stromatolites , their lack of distinctive morphology prevents them from being used to examine the history of bacterial evolution, or to date the time of origin of a particular bacterial species. However, gene sequences can be used to reconstruct the bacterial phylogeny , and these studies indicate that bacteria diverged first from the archaeal/eukaryotic lineage. [ 67 ] Bacteria were also involved in the second great evolutionary divergence, that of the archaea and eukaryotes. Here, eukaryotes resulted from the entering of ancient bacteria into endosymbiotic associations with the ancestors of eukaryotic cells, which were themselves possibly related to the Archaea . [ 68 ] [ 69 ] This involved the engulfment by proto-eukaryotic cells of alphaproteobacterial symbionts to form either mitochondria or hydrogenosomes , which are still found in all known Eukarya. Later on, some eukaryotes that already contained mitochondria also engulfed cyanobacterial-like organisms. This led to the formation of chloroplasts in algae and plants. There are also some algae that originated from even later endosymbiotic events. Here, eukaryotes engulfed a eukaryotic algae that developed into a "second-generation" plastid. [ 70 ] [ 71 ] This is known as secondary endosymbiosis .
Pelagibacter ubique and its relatives may be the most abundant organisms in the ocean, and it has been claimed that they are possibly the most abundant bacteria in the world. They make up about 25% of all microbial plankton cells, and in the summer they may account for approximately half the cells present in temperate ocean surface water. The total abundance of P. ubique and relatives is estimated to be about 2 × 10 28 microbes. [ 73 ] However, it was reported in Nature in February 2013 that the bacteriophage HTVC010P , which attacks P. ubique , has been discovered and "it probably really is the commonest organism on the planet". [ 74 ] [ 75 ]
The largest known bacterium, the marine Thiomargarita namibiensis , can be visible to the naked eye and sometimes attains 0.75 mm (750 μm). [ 76 ] [ 77 ]
The archaea (Greek for ancient [ 79 ] ) constitute a domain and kingdom of single-celled microorganisms . These microbes are prokaryotes , meaning they have no cell nucleus or any other membrane-bound organelles in their cells.
Archaea were initially classified as bacteria , but this classification is outdated. [ 80 ] Archaeal cells have unique properties separating them from the other two domains of life, Bacteria and Eukaryota . The Archaea are further divided into multiple recognized phyla . Classification is difficult because the majority have not been isolated in the laboratory and have only been detected by analysis of their nucleic acids in samples from their environment.
Archaea and bacteria are generally similar in size and shape, although a few archaea have very strange shapes, such as the flat and square-shaped cells of Haloquadratum walsbyi . [ 81 ] Despite this morphological similarity to bacteria, archaea possess genes and several metabolic pathways that are more closely related to those of eukaryotes, notably the enzymes involved in transcription and translation . Other aspects of archaeal biochemistry are unique, such as their reliance on ether lipids in their cell membranes , such as archaeols . Archaea use more energy sources than eukaryotes: these range from organic compounds , such as sugars, to ammonia , metal ions or even hydrogen gas . Salt-tolerant archaea (the Haloarchaea ) use sunlight as an energy source, and other species of archaea fix carbon ; however, unlike plants and cyanobacteria , no known species of archaea does both. Archaea reproduce asexually by binary fission , fragmentation , or budding ; unlike bacteria and eukaryotes, no known species forms spores .
Archaea are particularly numerous in the oceans, and the archaea in plankton may be one of the most abundant groups of organisms on the planet. Archaea are a major part of Earth's life and may play roles in both the carbon cycle and the nitrogen cycle . Thermoproteota (also known as eocytes or Crenarchaeota) are a phylum of archaea thought to be very abundant in marine environments and one of the main contributors to the fixation of carbon. [ 82 ]
All living organisms can be grouped as either prokaryotes or eukaryotes . Life originated as single-celled prokaryotes and later evolved into the more complex eukaryotes. In contrast to prokaryotic cells, eukaryotic cells are highly organised. Prokaryotes are the bacteria and archaea, while eukaryotes are the other life forms — protists , plants, fungi and animals. Protists are usually single-celled, while plants, fungi and animals are usually multi-celled .
It seems very plausible that the root of the eukaryotes lie within archaea; the closest relatives nowadays known may be the Heimdallarchaeota phylum of the proposed Asgard superphylum. This theory is a modern version of a scenario originally proposed in 1984 as Eocyte hypothesis , when Thermoproteota were the closest known archaeal relatives of eukaryotes then.
A possible transitional form of microorganism between a prokaryote and a eukaryote was discovered in 2012 by Japanese scientists. Parakaryon myojinensis is a unique microorganism larger than a typical prokaryote, but with nuclear material enclosed in a membrane as in a eukaryote, and the presence of endosymbionts . This is seen to be the first plausible evolutionary form of microorganism, showing a stage of development from the prokaryote to the eukaryote. [ 83 ] [ 84 ]
Protists are eukaryotes that cannot be classified as plants, fungi or animals. They are usually single-celled and microscopic. Life originated as single-celled prokaryotes (bacteria and archaea) and later evolved into more complex eukaryotes . Eukaryotes are the more developed life forms known as plants, animals, fungi and protists. The term protist came into use historically as a term of convenience for eukaryotes that cannot be strictly classified as plants, animals or fungi. They are not a part of modern cladistics, because they are paraphyletic (lacking a common ancestor).
Protists can be broadly divided into four groups depending on whether their nutrition is plant-like, animal-like, fungal-like, [ 85 ] or a mixture of these. [ 86 ]
Protists are highly diverse organisms currently organised into 18 phyla, but are not easy to classify. [ 89 ] [ 90 ] Studies have shown high protist diversity exists in oceans, deep sea-vents and river sediments, suggesting a large number of eukaryotic microbial communities have yet to be discovered. [ 91 ] [ 92 ] There has been little research on mixotrophic protists, but recent studies in marine environments found mixotrophic protests contribute a significant part of the protist biomass . [ 87 ] Since protists are eukaryotes they possess within their cell at least one nucleus , as well as organelles such as mitochondria and Golgi bodies . Protists are asexual but can reproduce rapidly through mitosis or by fragmentation .
In contrast to the cells of prokaryotes, the cells of eukaryotes are highly organised. Plants, animals and fungi are usually multi-celled and are typically macroscopic . Most protists are single-celled and microscopic. But there are exceptions. Some single-celled marine protists are macroscopic. Some marine slime molds have unique life cycles that involve switching between unicellular, colonial , and multicellular forms. [ 95 ] Other marine protist are neither single-celled nor microscopic, such as seaweed .
Protists have been described as a taxonomic grab bag of misfits where anything that doesn't fit into one of the main biological kingdoms can be placed. [ 98 ] Some modern authors prefer to exclude multicellular organisms from the traditional definition of a protist, restricting protists to unicellular organisms. [ 99 ] [ 100 ] This more constrained definition excludes many brown , multicellular red and green algae , and slime molds . [ 101 ]
Another way of categorising protists is according to their mode of locomotion. Many unicellular protists, particularly protozoans, are motile and can generate movement using flagella , cilia or pseudopods . Cells which use flagella for movement are usually referred to as flagellates , cells which use cilia are usually referred to as ciliates , and cells which use pseudopods are usually referred to as amoeba or amoeboids . Other protists are not motile , and consequently have no movement mechanism.
Flagellates include bacteria as well as protists. The rotary motor model used by bacteria uses the protons of an electrochemical gradient in order to move their flagella. Torque in the flagella of bacteria is created by particles that conduct protons around the base of the flagellum. The direction of rotation of the flagella in bacteria comes from the occupancy of the proton channels along the perimeter of the flagellar motor. [ 107 ]
Ciliates generally have hundreds to thousands of cilia that are densely packed together in arrays. During movement, an individual cilium deforms using a high-friction power stroke followed by a low-friction recovery stroke. Since there are multiple cilia packed together on an individual organism, they display collective behavior in a metachronal rhythm . This means the deformation of one cilium is in phase with the deformation of its neighbor, causing deformation waves that propagate along the surface of the organism. These propagating waves of cilia are what allow the organism to use the cilia in a coordinated manner to move. A typical example of a ciliated microorganism is the Paramecium , a one-celled, ciliated protozoan covered by thousands of cilia. The cilia beating together allow the Paramecium to propel through the water at speeds of 500 micrometers per second. [ 108 ]
Over 1500 species of fungi are known from marine environments. [ 109 ] These are parasitic on marine algae or animals, or are saprobes feeding on dead organic matter from algae, corals, protozoan cysts, sea grasses, and other substrata. [ 110 ] Spores of many species have special appendages which facilitate attachment to the substratum. [ 111 ] Marine fungi can also be found in sea foam and around hydrothermal areas of the ocean. [ 112 ] A diverse range of unusual secondary metabolites is produced by marine fungi. [ 113 ]
Mycoplankton are saprotropic members of the plankton communities of marine and freshwater ecosystems . [ 114 ] [ 115 ] They are composed of filamentous free-living fungi and yeasts associated with planktonic particles or phytoplankton . [ 116 ] Similar to bacterioplankton , these aquatic fungi play a significant role in heterotrophic mineralization and nutrient cycling . [ 117 ] While mostly microscopic, some mycoplankton can be up to 20 mm in diameter and over 50 mm in length. [ 118 ]
A typical milliliter of seawater contains about 10 3 to 10 4 fungal cells. [ 119 ] This number is greater in coastal ecosystems and estuaries due to nutritional runoff from terrestrial communities. A higher diversity of mycoplankton is found around coasts and in surface waters down to 1000 metres, with a vertical profile that depends on how abundant phytoplankton is. [ 120 ] [ 121 ] This profile changes between seasons due to changes in nutrient availability. [ 122 ] Marine fungi survive in a constant oxygen deficient environment, and therefore depend on oxygen diffusion by turbulence and oxygen generated by photosynthetic organisms . [ 123 ]
Marine fungi can be classified as: [ 123 ]
Lichens are mutualistic associations between a fungus, usually an ascomycete , and an alga or a cyanobacterium . Several lichens are found in marine environments. [ 124 ] Many more occur in the splash zone , where they occupy different vertical zones depending on how tolerant they are to submersion. [ 125 ] Some lichens live a long time; one species has been dated at 8,600 years. [ 126 ] However their lifespan is difficult to measure because what defines the same lichen is not precise. [ 127 ] Lichens grow by vegetatively breaking off a piece, which may or may not be defined as the same lichen, and two lichens of different ages can merge, raising the issue of whether it is the same lichen. [ 127 ]
The sea snail Littoraria irrorata damages plants of Spartina in the sea marshes where it lives, which enables spores of intertidal ascomycetous fungi to colonise the plant. The snail then eats the fungal growth in preference to the grass itself. [ 128 ]
According to fossil records, fungi date back to the late Proterozoic era 900-570 million years ago. Fossil marine lichens 600 million years old have been discovered in China. [ 129 ] It has been hypothesized that mycoplankton evolved from terrestrial fungi, likely in the Paleozoic era (390 million years ago). [ 130 ]
As juveniles, animals develop from microscopic stages, which can include spores , eggs and larvae . At least one microscopic animal group, the parasitic cnidarian Myxozoa , is unicellular in its adult form, and includes marine species. Other adult marine microanimals are multicellular. Microscopic adult arthropods are more commonly found inland in freshwater, but there are marine species as well. Microscopic adult marine crustaceans include some copepods , cladocera and tardigrades (water bears). Some marine nematodes and rotifers are also too small to be recognised with the naked eye, as are many loricifera , including the recently discovered anaerobic species that spend their lives in an anoxic environment. [ 131 ] [ 132 ] Copepods contribute more to the secondary productivity and carbon sink of the world oceans than any other group of organisms.
Primary producers are the autotroph organisms that make their own food instead of eating other organisms. This means primary producers become the starting point in the food chain for heterotroph organisms that do eat other organisms. Some marine primary producers are specialised bacteria and archaea which are chemotrophs , making their own food by gathering around hydrothermal vents and cold seeps and using chemosynthesis . However most marine primary production comes from organisms which use photosynthesis on the carbon dioxide dissolved in the water. This process uses energy from sunlight to convert water and carbon dioxide [ 133 ] : 186–187 into sugars that can be used both as a source of chemical energy and of organic molecules that are used in the structural components of cells. [ 133 ] : 1242 Marine primary producers are important because they underpin almost all marine animal life by generating most of the oxygen and food that provide other organisms with the chemical energy they need to exist.
The principal marine primary producers are cyanobacteria , algae and marine plants. The oxygen released as a by-product of photosynthesis is needed by nearly all living things to carry out cellular respiration . In addition, primary producers are influential in the global carbon and water cycles. They stabilize coastal areas and can provide habitats for marine animals. The term division has been traditionally used instead of phylum when discussing primary producers, but the International Code of Nomenclature for algae, fungi, and plants now accepts both terms as equivalents. [ 134 ]
Cyanobacteria were the first organisms to evolve an ability to turn sunlight into chemical energy. They form a phylum (division) of bacteria which range from unicellular to filamentous and include colonial species . They are found almost everywhere on earth: in damp soil, in both freshwater and marine environments, and even on Antarctic rocks. [ 136 ] In particular, some species occur as drifting cells floating in the ocean, and as such were amongst the first of the phytoplankton .
The first primary producers that used photosynthesis were oceanic cyanobacteria about 2.3 billion years ago. [ 137 ] [ 138 ] The release of molecular oxygen by cyanobacteria as a by-product of photosynthesis induced global changes in the Earth's environment. Because oxygen was toxic to most life on Earth at the time, this led to the near-extinction of oxygen-intolerant organisms , a dramatic change which redirected the evolution of the major animal and plant species. [ 139 ]
The tiny (0.6 μm ) marine cyanobacterium Prochlorococcus , discovered in 1986, forms today an important part of the base of the ocean food chain and accounts for much of the photosynthesis of the open ocean [ 140 ] and an estimated 20% of the oxygen in the Earth's atmosphere. [ 141 ] It is possibly the most plentiful genus on Earth: a single millilitre of surface seawater may contain 100,000 cells or more. [ 142 ]
Originally, biologists thought cyanobacteria was algae, and referred to it as "blue-green algae". The more recent view is that cyanobacteria are bacteria, and hence are not even in the same Kingdom as algae. Most authorities exclude all prokaryotes , and hence cyanobacteria from the definition of algae. [ 143 ] [ 144 ]
Algae is an informal term for a widespread and diverse group of photosynthetic protists which are not necessarily closely related and are thus polyphyletic . Marine algae can be divided into six groups: green , red and brown algae , euglenophytes , dinoflagellates and diatoms .
Dinoflagellates and diatoms are important components of marine algae and have their own sections below. Euglenophytes are a phylum of unicellular flagellates with only a few marine members.
Not all algae are microscopic. Green, red and brown algae all have multicellular macroscopic forms that make up the familiar seaweeds . Green algae , an informal group, contains about 8,000 recognised species. [ 145 ] Many species live most of their lives as single cells or are filamentous, while others form colonies made up from long chains of cells, or are highly differentiated macroscopic seaweeds. Red algae , a (disputed) phylum contains about 7,000 recognised species, [ 146 ] mostly multicellular and including many notable seaweeds. [ 146 ] [ 147 ] Brown algae form a class containing about 2,000 recognised species, [ 148 ] mostly multicellular and including many seaweeds such as kelp .
Unlike higher plants, algae lack roots, stems, or leaves. They can be classified by size as microalgae or macroalgae .
Microalgae are the microscopic types of algae, not visible to the naked eye. They are mostly unicellular species which exist as individuals or in chains or groups, though some are multicellular . Microalgae are important components of the marine protists discussed above , as well as the phytoplankton discussed below . They are very diverse . It has been estimated there are 200,000-800,000 species of which about 50,000 species have been described. [ 149 ] Depending on the species, their sizes range from a few micrometers (μm) to a few hundred micrometers. They are specially adapted to an environment dominated by viscous forces.
Unicellular organisms are usually microscopic. There are exceptions. Mermaid's wineglass , a genus of subtropical green algae , is single-celled but remarkably large and complex in form with a single large nucleus, making it a model organism for studying cell biology . [ 150 ] Another single-celled algae, Caulerpa taxifolia , has the appearance of a vascular plant including "leaves" arranged neatly up stalks like a fern. Selective breeding in aquariums to produce hardier strains resulted in an accidental release into the Mediterranean where it has become an invasive species known colloquially as killer algae . [ 151 ]
Macroalgae are the larger, multicellular and more visible types of algae, commonly called seaweeds . Seaweeds usually grow in shallow coastal waters where they are anchored to the seafloor by a holdfast . Like microalgae, macroalgae (seaweeds) can be regarded as marine protists since they are not true plants. But they are not microorganisms, so they are not within the scope of this article.
Plankton (from Greek for wanderers ) are a diverse group of organisms that live in the water column of large bodies of water but cannot swim against a current. As a result, they wander or drift with the currents. [ 153 ] Plankton are defined by their ecological niche , not by any phylogenetic or taxonomic classification. They are a crucial source of food for many marine animals, from forage fish to whales . Plankton can be divided into a plant-like component and an animal component.
Phytoplankton are the plant-like components of the plankton community ("phyto" comes from the Greek for plant ). They are autotrophic (self-feeding), meaning they generate their own food and do not need to consume other organisms.
Phytoplankton perform three crucial functions: they generate nearly half of the world atmospheric oxygen, they regulate ocean and atmospheric carbon dioxide levels, and they form the base of the marine food web . When conditions are right, blooms of phytoplankton algae can occur in surface waters. Phytoplankton are r-strategists which grow rapidly and can double their population every day. The blooms can become toxic and deplete the water of oxygen. However, phytoplankton numbers are usually kept in check by the phytoplankton exhausting available nutrients and by grazing zooplankton. [ 156 ]
Phytoplankton consist mainly of microscopic photosynthetic eukaryotes which inhabit the upper sunlit layer in all oceans. They need sunlight so they can photosynthesize. Most phytoplankton are single-celled algae, but other phytoplankton are bacteria and some are protists . [ 157 ] Phytoplankton include cyanobacteria (above) , diatoms , various other types of algae (red, green, brown, and yellow-green), dinoflagellates , euglenoids , coccolithophorids , cryptomonads , chlorophytes , prasinophytes , and silicoflagellates . They form the base of the primary production that drives the ocean food web , and account for half of the current global primary production, more than the terrestrial forests. [ 158 ]
Diatoms form a (disputed) phylum containing about 100,000 recognised species of mainly unicellular algae. Diatoms generate about 20 per cent of the oxygen produced on the planet each year, [ 93 ] take in over 6.7 billion metric tons of silicon each year from the waters in which they live, [ 159 ] and contribute nearly half of the organic material found in the oceans.
Diatoms are enclosed in protective silica (glass) shells called frustules . Each frustule is made from two interlocking parts covered with tiny holes through which the diatom exchanges nutrients and wastes. [ 156 ] The frustules of dead diatoms drift to the ocean floor where, over millions of years, they can build up as much as half a mile deep . [ 160 ]
Coccolithophores are minute unicellular photosynthetic protists with two flagella for locomotion. Most of them are protected by a shell covered with ornate circular plates or scales called coccoliths . The coccoliths are made from calcium carbonate. The calcite shells are important to the marine carbon cycle. [ 163 ] The term coccolithophore derives from the Greek for a seed carrying stone , referring to their small size and the coccolith stones they carry. Under the right conditions they bloom, like other phytoplankton, and can turn the ocean milky white. [ 164 ]
Phototrophic metabolism relies on one of three energy-converting pigments: chlorophyll , bacteriochlorophyll , and retinal . Retinal is the chromophore found in rhodopsins . The significance of chlorophyll in converting light energy has been written about for decades, but phototrophy based on retinal pigments is just beginning to be studied. [ 166 ]
In 2000 a team of microbiologists led by Edward DeLong made a crucial discovery in the understanding of the marine carbon and energy cycles. They discovered a gene in several species of bacteria [ 168 ] [ 169 ] responsible for production of the protein rhodopsin , previously unheard of in bacteria. These proteins found in the cell membranes are capable of converting light energy to biochemical energy due to a change in configuration of the rhodopsin molecule as sunlight strikes it, causing the pumping of a proton from inside out and a subsequent inflow that generates the energy. [ 170 ] The archaeal-like rhodopsins have subsequently been found among different taxa, protists as well as in bacteria and archaea, though they are rare in complex multicellular organisms . [ 171 ] [ 172 ] [ 173 ]
Research in 2019 shows these "sun-snatching bacteria" are more widespread than previously thought and could change how oceans are affected by global warming. "The findings break from the traditional interpretation of marine ecology found in textbooks, which states that nearly all sunlight in the ocean is captured by chlorophyll in algae. Instead, rhodopsin-equipped bacteria function like hybrid cars, powered by organic matter when available — as most bacteria are — and by sunlight when nutrients are scarce." [ 174 ] [ 166 ]
There is an astrobiological conjecture called the Purple Earth hypothesis which surmises that original life forms on Earth were retinal-based rather than chlorophyll-based, which would have made the Earth appear purple instead of green. [ 175 ] [ 176 ]
During the 1930s Alfred C. Redfield found similarities between the composition of elements in phytoplankton and the major dissolved nutrients in the deep ocean. [ 177 ] Redfield proposed that the ratio of carbon to nitrogen to phosphorus (106:16:1) in the ocean was controlled by the phytoplankton's requirements, as phytoplankton subsequently release nitrogen and phosphorus as they remineralize. This ratio has become known as the Redfield ratio , and is used as a fundamental principle in describing the stoichiometry of seawater and phytoplankton evolution. [ 178 ]
However, the Redfield ratio is not a universal value and can change with things like geographical latitude. [ 179 ] Based on allocation of resources, phytoplankton can be classified into three different growth strategies: survivalist, bloomer and generalist. Survivalist phytoplankton has a high N:P ratio (>30) and contains an abundance of resource-acquisition machinery to sustain growth under scarce resources. Bloomer phytoplankton has a low N:P ratio (<10), contains a high proportion of growth machinery and is adapted to exponential growth. Generalist phytoplankton has similar N:P to the Redfield ratio and contain relatively equal resource-acquisition and growth machinery. [ 178 ]
The f-ratio is the fraction of total primary production fuelled by nitrate (as opposed to that fuelled by other nitrogen compounds such as ammonium ). The ratio was originally defined by Richard Eppley and Bruce Peterson in one of the first papers estimating global oceanic production. [ 180 ]
Zooplankton are the animal component of the planktonic community ("zoo" comes from the Greek for animal ). They are heterotrophic (other-feeding), meaning they cannot produce their own food and must consume instead other plants or animals as food. In particular, this means they eat phytoplankton.
Zooplankton are generally larger than phytoplankton, mostly still microscopic but some can be seen with the naked eye. Many protozoans (single-celled protists that prey on other microscopic life) are zooplankton, including zooflagellates , foraminiferans , radiolarians , some dinoflagellates and marine microanimals . Macroscopic zooplankton (not generally covered in this article) include pelagic cnidarians , ctenophores , molluscs , arthropods and tunicates , as well as planktonic arrow worms and bristle worms .
Microzooplankton: major grazers of the plankton...
Many species of protozoa ( eukaryotes ) and bacteria ( prokaryotes ) prey on other microorganisms; the feeding mode is evidently ancient, and evolved many times in both groups. [ 181 ] [ 182 ] [ 183 ] Among freshwater and marine zooplankton , whether single-celled or multi-cellular, predatory grazing on phytoplankton and smaller zooplankton is common, and found in many species of nanoflagellates , dinoflagellates , ciliates , rotifers , a diverse range of meroplankton animal larvae, and two groups of crustaceans, namely copepods and cladocerans . [ 184 ]
Radiolarians are unicellular predatory protists encased in elaborate globular shells usually made of silica and pierced with holes. Their name comes from the Latin for "radius". They catch prey by extending parts of their body through the holes. As with the silica frustules of diatoms, radiolarian shells can sink to the ocean floor when radiolarians die and become preserved as part of the ocean sediment . These remains, as microfossils , provide valuable information about past oceanic conditions. [ 185 ]
Like radiolarians, foraminiferans ( forams for short) are single-celled predatory protists, also protected with shells that have holes in them. Their name comes from the Latin for "hole bearers". Their shells, often called tests , are chambered (forams add more chambers as they grow). The shells are usually made of calcite, but are sometimes made of agglutinated sediment particles or chiton , and (rarely) of silica. Most forams are benthic, but about 40 species are planktic. [ 187 ] They are widely researched with well established fossil records which allow scientists to infer a lot about past environments and climates. [ 185 ]
A number of forams are mixotrophic ( see below ). These have unicellular algae as endosymbionts , from diverse lineages such as the green algae , red algae , golden algae , diatoms , and dinoflagellates . [ 187 ] Mixotrophic foraminifers are particularly common in nutrient-poor oceanic waters. [ 189 ] Some forams are kleptoplastic , retaining chloroplasts from ingested algae to conduct photosynthesis . [ 190 ]
Amoeba can be shelled ( testate ) or naked.
A mixotroph is an organism that can use a mix of different sources of energy and carbon , instead of having a single trophic mode on the continuum from complete autotrophy at one end to heterotrophy at the other. It is estimated that mixotrophs comprise more than half of all microscopic plankton. [ 192 ] There are two types of eukaryotic mixotrophs: those with their own chloroplasts , and those with endosymbionts —and others that acquire them through kleptoplasty or by enslaving the entire phototrophic cell. [ 193 ]
The distinction between plants and animals often breaks down in very small organisms. Possible combinations are photo- and chemotrophy , litho- and organotrophy , auto- and heterotrophy or other combinations of these. Mixotrophs can be either eukaryotic or prokaryotic . [ 194 ] They can take advantage of different environmental conditions. [ 195 ]
Recent studies of marine microzooplankton found 30–45% of the ciliate abundance was mixotrophic, and up to 65% of the amoeboid, foram and radiolarian biomass was mixotrophic. [ 87 ]
Phaeocystis is an important algal genus found as part of the marine phytoplankton around the world. It has a polymorphic life cycle, ranging from free-living cells to large colonies. [ 196 ] It has the ability to form floating colonies, where hundreds of cells are embedded in a gel matrix, which can increase massively in size during blooms . [ 197 ] As a result, Phaeocystis is an important contributor to the marine carbon [ 198 ] and sulfur cycles . [ 199 ] Phaeocystis species are endosymbionts to acantharian radiolarians. [ 200 ] [ 201 ]
Dinoflagellates are part of the algae group , and form a phylum of unicellular flagellates with about 2,000 marine species. [ 204 ] The name comes from the Greek "dinos" meaning whirling and the Latin "flagellum" meaning a whip or lash . This refers to the two whip-like attachments (flagella) used for forward movement. Most dinoflagellates are protected with red-brown, cellulose armour. Like other phytoplankton, dinoflagellates are r-strategists which under right conditions can bloom and create red tides . Excavates may be the most basal flagellate lineage. [ 102 ]
By trophic orientation dinoflagellates cannot be uniformly categorized. Some dinoflagellates are known to be photosynthetic , but a large fraction of these are in fact mixotrophic , combining photosynthesis with ingestion of prey ( phagotrophy ). [ 205 ] Some species are endosymbionts of marine animals and other protists, and play an important part in the biology of coral reefs . Others predate other protozoa, and a few forms are parasitic. Many dinoflagellates are mixotrophic and could also be classified as phytoplankton.
The toxic dinoflagellate Dinophysis acuta acquire chloroplasts from its prey. "It cannot catch the cryptophytes by itself, and instead relies on ingesting ciliates such as the red Myrionecta rubra , which sequester their chloroplasts from a specific cryptophyte clade (Geminigera/Plagioselmis/Teleaulax)". [ 202 ]
Dinoflagellates often live in symbiosis with other organisms. Many nassellarian radiolarians house dinoflagellate symbionts within their tests. [ 207 ] The nassellarian provides ammonium and carbon dioxide for the dinoflagellate, while the dinoflagellate provides the nassellarian with a mucous membrane useful for hunting and protection against harmful invaders. [ 208 ] There is evidence from DNA analysis that dinoflagellate symbiosis with radiolarians evolved independently from other dinoflagellate symbioses, such as with foraminifera . [ 209 ]
Some dinoflagellates are bioluminescent . At night, ocean water can light up internally and sparkle with blue light because of these dinoflagellates. [ 210 ] [ 211 ] Bioluminescent dinoflagellates possess scintillons , individual cytoplasmic bodies which contain dinoflagellate luciferase , the main enzyme involved in the luminescence. The luminescence, sometimes called the phosphorescence of the sea , occurs as brief (0.1 sec) blue flashes or sparks when individual scintillons are stimulated, usually by mechanical disturbances from, for example, a boat or a swimmer or surf. [ 212 ]
Sediments at the bottom of the ocean have two main origins, terrigenous and biogenous.
Terrigenous sediments account for about 45% of the total marine sediment, and originate in the erosion of rocks on land, transported by rivers and land runoff, windborne dust, volcanoes, or grinding by glaciers.
Biogenous sediments account for the other 55% of the total sediment, and originate in the skeletal remains of marine protists (single-celled plankton and benthos microorganisms). Much smaller amounts of precipitated minerals and meteoric dust can also be present. Ooze , in the context of a marine sediment, does not refer to the consistency of the sediment but to its biological origin. The term ooze was originally used by John Murray , the "father of modern oceanography", who proposed the term radiolarian ooze for the silica deposits of radiolarian shells brought to the surface during the Challenger expedition . [ 217 ] A biogenic ooze is a pelagic sediment containing at least 30 per cent from the skeletal remains of marine organisms.
Marine microbenthos are microorganisms that live in the benthic zone of the ocean – that live near or on the seafloor, or within or on surface seafloor sediments. The word benthos comes from Greek, meaning "depth of the sea". Microbenthos are found everywhere on or about the seafloor of continental shelves, as well as in deeper waters, with greater diversity in or on seafloor sediments. In shallow waters, seagrass meadows , coral reefs and kelp forests provide particularly rich habitats. In photic zones benthic diatoms dominate as photosynthetic organisms. In intertidal zones changing tides strongly control opportunities for microbenthos.
Both foraminifera and diatoms have planktonic and benthic forms, that is, they can drift in the water column or live on sediment at the bottom of the ocean. Either way, their shells end up on the seafloor after they die. These shells are widely used as climate proxies . The chemical composition of the shells are a consequence of the chemical composition of the ocean at the time the shells were formed. Past water temperatures can be also be inferred from the ratios of stable oxygen isotopes in the shells, since lighter isotopes evaporate more readily in warmer water leaving the heavier isotopes in the shells. Information about past climates can be inferred further from the abundance of forams and diatoms, since they tend to be more abundant in warm water. [ 223 ]
The sudden extinction event which killed the dinosaurs 66 million years ago also rendered extinct three-quarters of all other animal and plant species. However, deep-sea benthic forams flourished in the aftermath. In 2020 it was reported that researchers have examined the chemical composition of thousands of samples of these benthic forams and used their findings to build the most detailed climate record of Earth ever. [ 224 ] [ 225 ]
Some endoliths have extremely long lives. In 2013 researchers reported evidence of endoliths in the ocean floor, perhaps millions of years old, with a generation time of 10,000 years. [ 226 ] These are slowly metabolizing and not in a dormant state. Some Actinomycetota found in Siberia are estimated to be half a million years old. [ 227 ] [ 228 ] [ 229 ]
The concept of the holobiont was initially defined by Dr. Lynn Margulis in her 1991 book Symbiosis as a Source of Evolutionary Innovation as an assemblage of a host and the many other species living in or around it, which together form a discrete ecological unit . [ 231 ] The components of a holobiont are individual species or bionts , while the combined genome of all bionts is the hologenome . [ 232 ]
The concept has subsequently evolved since this original definition, [ 233 ] with the focus moving to the microbial species associated with the host. Thus the holobiont includes the host, virome , microbiome , and other members, all of which contribute in some way to the function of the whole. [ 234 ] [ 235 ] A holobiont typically includes a eukaryote host and all of the symbiotic viruses , bacteria , fungi , etc. that live on or inside it. [ 236 ]
However, there is controversy over whether holobionts can be viewed as single evolutionary units. [ 237 ]
Reef-building corals are well-studied holobionts that include the coral itself (a eukaryotic invertebrate within class Anthozoa ), photosynthetic dinoflagellates called zooxanthellae ( Symbiodinium ), and associated bacteria and viruses. [ 238 ] Co-evolutionary patterns exist for coral microbial communities and coral phylogeny. [ 239 ]
Marine microorganisms play central roles in the marine food web .
The viral shunt pathway is a mechanism that prevents marine microbial particulate organic matter (POM) from migrating up trophic levels by recycling them into dissolved organic matter (DOM), which can be readily taken up by microorganisms. [ 244 ] Viral shunting helps maintain diversity within the microbial ecosystem by preventing a single species of marine microbe from dominating the micro-environment. [ 245 ] The DOM recycled by the viral shunt pathway is comparable to the amount generated by the other main sources of marine DOM. [ 246 ]
Sea ice microbial communities (SIMCO) refer to groups of microorganisms living within and at the interfaces of sea ice at the poles. The ice matrix they inhabit has strong vertical gradients of salinity, light, temperature and nutrients. Sea ice chemistry is most influenced by the salinity of the brine which affects the pH and the concentration of dissolved nutrients and gases. The brine formed during the melting sea ice creates pores and channels in the sea ice in which these microbes can live. As a result of these gradients and dynamic conditions, a higher abundance of microbes are found in the lower layer of the ice, although some are found in the middle and upper layers. [ 251 ]
Hydrothermal vents are located where the tectonic plates are moving apart and spreading. This allows water from the ocean to enter into the crust of the earth where it is heated by the magma. The increasing pressure and temperature forces the water back out of these openings, on the way out, the water accumulates dissolved minerals and chemicals from the rocks that it encounters. Vents can be characterized by temperature and chemical composition as diffuse vents which release clear relatively cool water usually below 30 °C, as white smokers which emit milky coloured water at warmer temperatures, about 200-330 °C, and as black smokers which emit water darkened by accumulated precipitates of sulfide at hot temperatures, about 300-400 °C. [ 252 ]
Hydrothermal vent microbial communities are microscopic unicellular organisms that live and reproduce in the chemically distinct area around hydrothermal vents. These include organisms in microbial mats , free floating cells, and bacteria in endosymbiotic relationships with animals. Because there is no sunlight at these depths, energy is provided by chemosynthesis where symbiotic bacteria and archaea form the bottom of the food chain and are able to support a variety of organisms such as giant tube worms and Pompeii worms . These organisms utilize this symbiotic relationship in order to utilize and obtain the chemical energy that is released at these hydrothermal vent areas. [ 253 ] Chemolithoautotrophic bacteria can derive nutrients and energy from the geological activity at a hydrothermal vent to fix carbon into organic forms. [ 254 ]
Viruses are also a part of the hydrothermal vent microbial community and their influence on the microbial ecology in these ecosystems is a burgeoning field of research. [ 255 ] Viruses are the most abundant life in the ocean, harboring the greatest reservoir of genetic diversity. [ 256 ] As their infections are often fatal, they constitute a significant source of mortality and thus have widespread influence on biological oceanographic processes, evolution and biogeochemical cycling within the ocean. [ 257 ] Evidence has been found however to indicate that viruses found in vent habitats have adopted a more mutualistic than parasitic evolutionary strategy in order to survive the extreme and volatile environment they exist in. [ 258 ] Deep-sea hydrothermal vents were found to have high numbers of viruses indicating high viral production. [ 259 ] Like in other marine environments, deep-sea hydrothermal viruses affect abundance and diversity of prokaryotes and therefore impact microbial biogeochemical cycling by lysing their hosts to replicate. [ 260 ] However, in contrast to their role as a source of mortality and population control, viruses have also been postulated to enhance survival of prokaryotes in extreme environments, acting as reservoirs of genetic information. The interactions of the virosphere with microorganisms under environmental stresses is therefore thought to aide microorganism survival through dispersal of host genes through horizontal gene transfer . [ 261 ]
The deep biosphere is that part of the biosphere that resides below the first few meters of the surface. It extends at least 5 kilometers below the continental surface and 10.5 kilometers below the sea surface, with temperatures that may exceed 100 °C.
Above the surface living organisms consume organic matter and oxygen. Lower down, these are not available, so they make use of "edibles" ( electron donors ) such as hydrogen released from rocks by various chemical processes, methane, reduced sulfur compounds and ammonium. They "breathe" electron acceptors such as nitrates and nitrites, manganese and iron oxides, oxidized sulfur compounds and carbon dioxide.
There is very little energy at greater depths, and metabolism can be up to a million times slower than at the surface. Cells may live for thousands of years before dividing and there is no known limit to their age. The subsurface accounts for about 90% of the biomass in bacteria and archaea, and 15% of the total biomass for the biosphere. Eukaryotes are also found, mostly microscopic, but including some multicellular life. Viruses are also present and infect the microbes.
In 2018, researchers from the Deep Carbon Observatory announced that life forms , including 70% of the bacteria and archaea on Earth, totaling a biomass of 23 billion tonnes carbon , live up to 4.8 km (3.0 mi) deep underground, including 2.5 km (1.6 mi) below the seabed. [ 262 ] [ 263 ] [ 264 ] In 2019 microbial organisms were discovered living 7,900 feet (2,400 m) below the surface, breathing sulfur and eating rocks such as pyrite as their regular food source. [ 265 ] [ 266 ] [ 267 ] This discovery occurred in the oldest known water on Earth. [ 268 ]
In 2020 researchers reported they had found what could be the longest-living life forms ever: aerobic microorganisms which had been in quasi-suspended animation for up to 101.5 million years. The microorganisms were found in organically poor sediments 68.9 metres (226 feet) below the seafloor in the South Pacific Gyre (SPG), "the deadest spot in the ocean". [ 269 ] [ 270 ]
To date biologists have been unable to culture in the laboratory the vast majority of microorganisms. This applies particularly to bacteria and archaea, and is due to a lack of knowledge or ability to supply the required growth conditions. [ 271 ] [ 272 ] The term microbial dark matter has come to be used to describe microorganisms scientists know are there but have been unable to culture, and whose properties therefore remain elusive. [ 271 ] Microbial dark matter is unrelated to the dark matter of physics and cosmology, but is so-called for the difficulty in effectively studying it. It is hard to estimate its relative magnitude, but the accepted gross estimate is that less than one per cent of microbial species in a given ecological niche is culturable. In recent years effort is being put to decipher more of the microbial dark matter by means of learning their genome DNA sequence from environmental samples [ 273 ] and then by gaining insights to their metabolism from their sequenced genome, promoting the knowledge required for their cultivation.
Traditionally, the phylogeny of microorganisms was inferred and their taxonomy was established based on studies of morphology . However, developments in molecular phylogenetics have allowed evolutionary relationship of species to be established by analyzing deeper characteristics, such as their DNA and protein sequences, for example ribosomal DNA . [ 278 ] The lack of easily accessible morphological features, such as those present in animals and plants , particularly hampered early efforts at classifying bacteria and archaea. This resulted in erroneous, distorted and confused classification, an example of which, noted Carl Woese , is Pseudomonas whose etymology ironically matched its taxonomy, namely "false unit". [ 279 ] Many bacterial taxa have been reclassified or redefined using molecular phylogenetics.
Recent developments in molecular sequencing have allowed for the recovery of genomes in situ , directly from environmental samples and avoiding the need for culturing. This has led for example, to a rapid expansion in knowledge of the diversity of bacterial phyla . These techniques are genome-resolved metagenomics and single-cell genomics .
The new sequencing technologies and the accumulation of sequence data have resulted in a paradigm shift, highlighted both the ubiquity of microbial communities in association within higher organisms and the critical roles of microbes in ecosystem health. [ 283 ] These new possibilities have revolutionized microbial ecology , because the analysis of genomes and metagenomes in a high-throughput manner provides efficient methods for addressing the functional potential of individual microorganisms as well as of whole communities in their natural habitats. [ 284 ] [ 285 ] [ 286 ]
Omics is a term used informally to refer to branches of biology whose names end in the suffix -omics , such as genomics , proteomics , metabolomics , and glycomics . Marine Omics has recently emerged as a field of research of its own. [ 288 ] Omics aims at collectively characterising and quantifying pools of biological molecules that translate into the structure, function, and dynamics of an organism or organisms. For example, functional genomics aims at identifying the functions of as many genes as possible of a given organism. It combines different -omics techniques such as transcriptomics and proteomics with saturated mutant collections. [ 289 ] [ 290 ]
Many omes beyond the original genome have become useful and have been widely adopted in recent years by research scientists. The suffix -omics can provide an easy shorthand to encapsulate a field; for example, an interactomics study is reasonably recognisable as relating to large-scale analyses of gene-gene, protein-protein, or protein-ligand interactions, while proteomics has become established as a term for studying proteins on a large scale.
Any given omics technique, used just by itself, cannot adequately disentangle the intricacies of a host microbiome . Multi-omics approaches are needed to satisfactorily unravel the complexities of the host-microbiome interactions. [ 291 ] For instance, metagenomics , metatranscriptomics , metaproteomics and metabolomics methods are all used to provide information on the metagenome . [ 292 ]
See...
In marine environments, microbial primary production contributes substantially to CO 2 sequestration . Marine microorganisms also recycle nutrients for use in the marine food web and in the process release CO 2 to the atmosphere. Microbial biomass and other organic matter (remnants of plants and animals) are converted to fossil fuels over millions of years. By contrast, burning of fossil fuels liberates greenhouse gases in a small fraction of that time. As a result, the carbon cycle is out of balance, and atmospheric CO 2 levels will continue to rise as long as fossil fuels continue to be burnt. [ 6 ]
Microorganisms have key roles in carbon and nutrient cycling, animal (including human) and plant health, agriculture and the global food web. Microorganisms live in all environments on Earth that are occupied by macroscopic organisms, and they are the sole life forms in other environments, such as the deep subsurface and ‘extreme’ environments. Microorganisms date back to the origin of life on Earth at least 3.8 billion years ago, and they will likely exist well beyond any future extinction events... Unless we appreciate the importance of microbial processes, we fundamentally limit our understanding of Earth's biosphere and response to climate change and thus jeopardize efforts to create an environmentally sustainable future. [ 6 ]
Marine microorganisms known as cyanobacteria first emerged in the oceans during the Precambrian era roughly 2 billion years ago. Over eons, the photosynthesis of marine microorganisms generated by oxygen has helped shape the chemical environment in the evolution of plants, animals and many other life forms. Marine microorganisms were first observed in 1675 by Dutch lensmaker Antonie van Leeuwenhoek . | https://en.wikipedia.org/wiki/Marine_microorganisms |
Marine navigation is the art and science of steering a ship from a starting point (sailing) to a destination, efficiently and responsibly. It is an art because of the skill that the navigator must have to avoid the dangers of navigation, and it is a science because it is based on physical , mathematical , oceanographic , cartographic , astronomical , and other knowledge.
Marine navigation can be surface or submarine .
Navigation (from the Latin word navigatio ) is the act of sailing or voyaging. Nautical (from Latin nautĭca , and this from Greek ναυτική [τέχνη] nautikḗ [téjne] "[art of] sailing" and from ναύτης nautes "sailor") is that pertaining to navigation and the science and art of sailing. Naval (from the Latin adjective navalis ) is that relating to ships and navigation, or particularly to the navy . [ 1 ]
In Ancient Rome , the navicularii conducted long-distance trade by sea.
Coastal navigation was practiced since the most ancient times. [ 2 ] The biblical account of the great flood , where the Noah's Ark appears, is based both on myths and on the navigational practice of the Mesopotamian civilizations , who from the Sumerians onwards navigated their two rivers ( Tigris and Euphrates ) and the Persian Gulf . The ancient Egyptians did not limit themselves to inland navigation of the Nile either, and used the Mediterranean sea routes existing since the Neolithic — through which cultural phenomena such as megalithism or the metallurgy would have spread for millennia. The Cretans even established a true thalassocracy (government of the seas, attributed to King Minos ) until the Mycenaean period (2nd millennium BC), when the events mythologized in the Homeric poems [ Note 1 ] ought to be placed.
The Hittites , led by King Šuppiluliuma II faced the Cyprus in the first historically recorded naval battle (ca. 1210 BC); at the same time, all the civilizations of the Eastern Mediterranean suffered from the incursions of the denominated " Sea Peoples ".
The Phoenicians — whom the Greeks considered their masters in navigation and who are also cited in the Bible — [ Note 2 ] [ 3 ] would have been the first Mediterranean civilization to sail the high seas by sculling and sailing , guided by the sun during the day and by the North Star at night. It is recorded that, crossing the Strait of Gibraltar — the "Rock of Gibraltar", the so-called " Pillars of Hercules " in the Greek myths — they sailed across the Atlantic Ocean reaching the south to some point on the west coast of Africa and the north to the British Isles (or even beyond, to the place that the texts call Thule ), but it is unclear if they circumnavigated Africa or crossed the Atlantic reaching America, something most likely achieved by the Norsemen in the 10th century.
In the Indian and Pacific oceans, the oceanic navigations made it possible to populate all the archipelagoes ( Polynesian navigation ). However, the possibility of reaching South America is still a matter of debate — the settlement of the Americas through the Bering Strait would not have required navigation, or in any case, coastal navigation would have sufficed — as well as other possible pre-Columbian transoceanic contacts . In the first quarter of the 15th century, the Chinese expeditions led by Zheng He reached the African coasts of the Indian Ocean. It has been proposed that they might have reached the South Atlantic and even America and Europe, but this proposal has not been accepted beyond mere speculation.
Mediterranean navigation, which the Romans had come to control (undisputed Mare Nostrum since their victories over the Carthaginians in the Punic Wars [264-146 BC], the Egyptians during the Battle of Actium [31 BC], and pirates ), was once again a contested environment in the Middle Ages , from the moment the Vandals managed to attack the Italian coasts from the sea. In the 6th century, the Byzantines managed to regain control, and in the 7th century it was the Arabs who ended up dividing the Mediterranean area , [ 5 ] which even the Vikings and Normans were able to access. Since the time of the Crusades , Venetian , [ 6 ] Genoese [ 7 ] and Crown of Aragon [ 8 ] navigators also had a strong presence. Knowledge of the compass , transmitted to the Europeans by the Arabs (who in turn had obtained it from the Chinese), together with other improvements in astronomical techniques ( astrolabe , Jacob's staff , sextant , cartographic techniques ( portulan and shipbuilding ( caravel , nau , galleon ), made the Age of Discovery — initially led by the Portuguese and Castilians — possible, especially after Henry the Navigator impulsed the school of Sagres . In 1492, the first voyage of Christopher Columbus took place. In 1488, Bartolomeu Dias rounded the Cape of Good Hope , which opened the route to the Indian Ocean — Vasco de Gama reached Calicut (India) in 1498. Between 1519 and 1521, the Magellan-Elcano expedition circumnavigated the world — measuring the geographical longitude with the method of its scientific organizer, Rui Faleiro . Until the 6th century, the Spanish-Portuguese hegemony in navigation was patent in fields such as geography and cosmography . Both English and French pilots learned to navigate from the texts of Pedro de Medina , Martín Fernández de Enciso and Martín Cortés , among others. [ 9 ] [ 10 ] The conjunction of "cannons and sails" has been argued to have given European states the advantage to prevail over the rest, [ 11 ] launching the modern " world system ". [ 12 ]
Since the 18th century, England exercised maritime hegemony, a fact that was confirmed in the early 19th century with the Battle of Trafalgar (1805). Among the main English expeditions of the time were Captain Cook 's (1768-1779), also the second expedition of the Beagle (1831-1836) — which was of great importance for the later development of Charles Darwin 's theory of evolution . Already fully in the age of steam navigation , techniques and vessels continued to be perfected in transoceanic sailing ( clipper ), that did not become obsolete for commercial navigation until the 20th century — especially after the opening of the Panama Canal . Even then, the unbridled optimism that characterized the naval design of the time suffered a severe blow with the sinking of the Titanic (1912).
Contemporary shipping has massively ceased to perform one of its traditional functions and has been replaced by aviation, such as passenger transport , although with two important exceptions: leisure travel ( tourism by cruise ships ) and irregular traffic of people ( irregular immigration ). Since the Second Industrial Revolution , the main volume of freight transport has been hydrocarbons ( oil tankers and gas tankers ). Other raw materials are also transported in bulk on cargo ships , but from 1956 onward, a large part of goods of all kinds were adapted to standardized containers that speed up loading and unloading, allowing a combination with land transport ( hub ). Highly technological navigation has reduced crews and increased the size of ships. For example, in deep-sea fishing , which locates its prey with sophisticated means and lasts indefinitely in time — freezer ships or factory ships — which in some circumstances has made them vulnerable to new forms of piracy.
These are the methods used in maritime navigation to solve the three problems of the navigator:
Navigation and location of the ship by positioning techniques based on the observation of bearings and distances to notable points on the coast ( lighthouses , capes , buoys , etc.) by visual means ( pelorus ), observation of horizontal angles ( sextant ) or electronic methods (bearings from radar to racons , transponders , etc.)
Navigation and location of the ship by analytical means, after considering the following elements: initial location, bearing (s) — whether absolute bearings , surface bearings, or relative bearings . Also velocity as well as the external factors that have influenced the course either partially or entirely, such as the wind ( leeway ) and/or the current (bearing of the current and hourly current intensity). The point obtained from the calculations is called the "Dead reckoning location", with its corresponding latitude and longitude . This point is also known as Fantasy point.
Navigation that follows a rhumb line — that is, all meridians are cut at the same angle. On a nautical chart following the Mercator projection , a loxodromic is represented by a straight line.
This type of navigation is useful for not too long distances, as it allows the course to remain steady, [ 16 ] but it does not offer the shortest distance.
Navigation that follows the shortest distance between two points, i.e., that which follows a great circle . Such routes yield the shortest distance between two points on the globe. [ 16 ] To calculate the bearing and distance between two points it is necessary to solve a spherical triangle whose vertices are the origin, the destination, and the pole. [ 17 ]
Navigation and location of the ship by geopositioning techniques based on the observation of the stars and other celestial bodies . The variables measured to find the location are: the observed angular height of the stars above the horizon , measured with the sextant (formerly with the astrolabe or other instrument), and the time , measured with the chronometer .
Conceptually, the process is not complex to understand:
In practice, the mathematical process, called "reduction" of the observation, can be complex for the uninitiated. To the height observed with the sextant, it is necessary to apply a series of corrections to compensate for atmospheric refraction, parallax and other errors. Once this is done, it is necessary to solve a spherical triangle by mathematical and trigonometric methods.
There are many methods to do this. The manual methods use tables ( trigonometric , logarithms , etc.) to facilitate the calculations. The introduction of calculators and electronic computers at the end of the 20th century greatly facilitated the calculation, but the creation of GPS made celestial navigation no longer important, relegating it to the background as an alternative method in case of failure of the on-board electronics or as a hobby of scientific interest.
Navigation and location of the ship by positioning techniques based on the aids provided by global positioning systems, such as GPS , GLONASS , or GALILEO . It is the system most widely spread and easiest to use, in spite of the errors that may arise.
Navigation and location of the ship by means of the analysis of the data provided by accelerometers and/or gyroscopes located on board, which integrate the accelerations experienced in complex electronic systems, that converted into velocities (in the 3 possible axes of displacement) and according to the observed courses, make it possible to obtain the location of the ship.
The harbinger of a successful navigation was the dolphin , which is why its representation became the symbol carried by all ships.
More recently, navigation was represented as a woman crowned with ship's sterns whose clothes are agitated by the winds. She rests one hand on a rudder and the other holds the instrument for measuring height. At her feet, the ampoule , the compass, the trident of Neptune and the riches of commerce, while the sea can be seen on the horizon, completed by a lighthouse and traversed by ships at full sail. [ 10 ] | https://en.wikipedia.org/wiki/Marine_navigation |
Nitrogen fixation is a vital biochemical process that supports the productivity of marine environments. It involves the conversion of nitrogen gas (N 2 ) to forms available to living organisms such as ammonia (NH 3 ), ammonium ( NH + 4 ), nitrate ( NO − 3 ), and nitrite ( NO − 2 ). [ 1 ] Since nitrogen is a limiting nutrient in most marine ecosystems, nitrogen fixation plays a key role in sustaining primary production, particularly in oligotrophic regions. Currently about 13 prokaryote genera are known to fix nitrogen. [ 2 ] Understanding marine nitrogen fixation is crucial to the study of global nitrogen cycling . Research indicates an imbalance between nitrogen fixation and denitrification rates, impacting nitrogen availability in different oceanic regions. [ 1 ]
Nitrogen was discovered in the 18th century, by the scientist Daniel Rutherford . [ 3 ] Nitrogen's importance in agriculture, plant growth and the nitrogen cycle became clear. However, at this time, marine nitrogen fixation remained unexplored. [ 3 ]
Biological nitrogen fixation was discovered by Herman Hellriegel and Hermann Wilfarth in 1880. [ 3 ] They discovered that the root nodules of legumes host nitrogen-fixing bacteria which convert atmospheric nitrogen gas into forms the plants could use. [ 3 ] In the 20th century, tracing techniques including nitrogen-15 isotopes were used to study nitrogen fixation in aquatic environments. Specifically, cyanobacteria such as Trichodesmium were found to be major nitrogen fixers in the ocean. This confirmed microbes' role as nitrogen fixers in aquatic environments.
While less common than bacteria, nitrogen fixation has also been identified within some Archaea among methanogenic species. [ 2 ] Historically, there has been a debate regarding how Archaea acquired the ability to fix nitrogen. One hypothesis, the bacteria-first hypothesis, suggests that the nitrogen fixation process evolved in bacteria before being transferred to Archaea via horizontal gene transfer. [ 4 ] The diversity and abundance of nitrogen-fixing bacteria, along with isotopic data and the distribution of specialized nitrogenase genes provide evidence supporting this theory. [ 4 ]
Nitrogen fixers are widespread throughout the world's oceans, but vary in density depending on the abundance of nutrients, light availability, oxygen levels, temperature and season. [ 5 ] [ 6 ] The highest density of marine nitrogen fixers is observed in the pelagic zone , where oligotrophic conditions require the fixation of inorganic dinitrogen (N 2 ) via biological processes. [ 5 ]
In oligotrophic waters, organic nitrogen is highly limited, reaching concentrations as below 1 μmol/L in the open ocean of the Mediterranean Sea . [ 7 ] Fixation is the only way to convert atmospheric nitrogen to an organic form usable by the surrounding ecosystem. The deep waters of the subtropical and tropical latitudes of the North Atlantic ocean , as well as the Mediterranean Sea, have the highest levels of fixation, dominated by the filamentous cyanobacteria Trichodesmium spp. [ 8 ] [ 9 ] This species uses the enzyme nitrogenase to provide approximately 100 to 150 million tonnes of nitrogen per year globally in the open ocean. [ 8 ] [ 5 ] [ 9 ]
The Pacific Ocean , especially at higher latitudes, acts as a sink for organic nitrogen. This is primarily due to the direct correlation between O 2 levels and nitrogen fixation rates. [ 5 ] The Pacific ocean performs Pacific meridional overturning circulation (PMOC) which pulls warmer waters from the Atlantic and subtopics into the upper latitudes of the Pacific. [ 10 ] By the time it reaches the deep ocean however, it is depleted of oxygen and filled with organic waste which creates large oxygen minimum zones (OMZ) where fixation is low and denitrification is high. [ 10 ] [ 11 ] Despite these processes, the Pacific is not devoid of fixation. [ 5 ] This ocean is dominated by single cell diazotrophs , particularly UCYN-A , which are capable of nitrification and can reach concentrations as high as 10 6 cells per litre, even in oligotrophic waters. [ 12 ] [ 6 ]
Fixation rates are lower in coastal systems compared to those of open waters. This is the result of a variety of factors, foremost being nutrient concentrations. [ 5 ] [ 12 ] Coastlines, which experience more upwelling in the higher latitudes, have less biotic nitrogen fixation. [ 13 ] They instead rely on biologically available notrogen existing in the ecosystem available as DOM or within organisms susceptible to grazing. [ 14 ] Additionally, Ammonium is made available in marine sediment via upwelling, with 76–83% organic nitrogen remineralized and redistributed by this process. [ 15 ] Nitrogen concentrations, in the form of ammonia and nitrate, can exceed 100 μmol/L in coastal upwelling regions. [ 13 ] [ 5 ] The increased concentrations of available nitrogen mean that even species capable of fixation will rely on existing materials, suspending the process of the more costly fixation, thereby reducing rates. The variation is also dependent on the concentrations of other macronutrients , with particular dependence on the N:P ratio with species needing both for proper biosynthesis. [ 5 ] Nitrogen fixation rates in surface waters ranged from below detection limits to 7.51 nmol N L −1 d −1 in coastal water depending on these varied factors. [ 16 ] Considering the seasonal variability of upwelling and nutrient abundance in costal waters means the fixation rates are dynamic with greater flux but on average, the productivity of costal ecosystems keeps nitrogen production low. [ 13 ] [ 14 ]
Nitrogenase operates exclusively under anaerobic conditions, [ 17 ] and while most species have systems to allow the mitigation of this problem, many nitrogen fixers have their highest production within anaerobic conditions. Additionally, marine sediments display lower concentrations of both nitrogen and phosphorus, particularly at lower depths. At only 6 cm depth, available nitrogen decreases by as much as 50%. [ 14 ] This is why a large amount of nitrogen fixation occurs within marine sediments . Fixation rates additionally vary with temperature of the sedimentary substrate. [ 13 ] The concentration of O 2 also varies alongside nutrient availability, penetrating less as temperature increases increasing competition for resources amongst heterotrophs. [ 14 ] [ 6 ]
Stable isotope tracers allow for both macro and micro scaled experiments. Using a variety of different isotopes, researchers can observe the distribution and uptake of different nutrients in diverse ecosystems . [ 18 ] Traditionally, these experiments track the incorporation of these radio nutrients into specific organisms but with the aid of satellite imaging and large scale sampling, they can track the incorporation into biomass of an ecosystem as a whole. [ 19 ]
Nitrogen experiments use the quasi-conservative tracer N* (Nstar) to track the linear relationship between Nitrogen and Phosphorus nitrification and denitrification. [ 19 ] N* is a stable Nitrogen tracer that displays a linear association with marine phosphorus and therefore provides a means of visualizing nitrogen and fixation in marine systems on a large scale. [ 5 ] [ 19 ]
Following the addition of N*, water samples are collected from various latitudes within the same gyre to track nitrogen distribution. [ 5 ] This method allows for the visualization of nitrogen distribution on a large scale and is often supplemented with satellite imaging to gather accurate distribution data. [ 18 ] Additionally, these experiment are used to calculate global fixation rates as well as the flux within these rates making it one of the best large scale research methods. [ 5 ]
PCR has a long standing relationship in genetic and microbiological experiments. By identifying genetic markers with functions specific to nitrogen fixation processes allows researchers to express and quantify those genes within marine samples, [ 20 ] allowing for approximate measurements of marine fixers density in varied ecosystems.
By quantifying the planktonic nifH genes through amplification , nitrogen fixation can be estimated in both filtered samples and laboratory cultures tracking the change over time under varied conditions. [ 16 ] [ 12 ] This process can also be used to identify and quantify species that cannot be cultured as the genetic markers are organism specific and are present in sample even following the lysis of cells. [ 12 ] [ 20 ]
Despite being easier, specifically with modern equipment, this method only provides estimates, not accurate counts due to bottling and other manipulatory effects present in most laboratory experiments. [ 12 ] Additionally, it only shows the density of microbes with the potential to perform nitrogen fixation, not the actual rate of expression. While this technique is a powerful tool, it is often supplemented with other tools for accurate measurements and analysis. [ 20 ]
The variability of marine ecosystems forces the majority of nitrification and fixation research to be performed in the lab. [ 19 ] Nitrification rates are calculated in a lab setting by comparing the concentrations of NO − 2 , NO − 3 , and NH + 4 following incubation of filtered marine samples either in specific cultures or in bottled samples. [ 8 ]
These experiments work for aquatic and sediment species dependent on their ability to survive in an enclosed system. [ 14 ] [ 6 ] Specific nitrogen-fixing species can be isolated on plates, but their often pseudo- anaerobic nature makes this difficult for many species. [ 14 ] Mesocosm experiments are not performed in the presence of diverse marine systems. Instead, their controlled, laboratory based methodology means that some factors of the traditionally dynamic marine systems may be missed and therefore, an understanding of the whole picture remains elusive. [ 21 ]
Nitrogen fixation is a complex biochemical process that requires energy and is influenced by various environmental factors. In the surface ocean, nitrogen fixers consume phosphate ( PO 3− 4 ) and iron (Fe n + ) to support their growth while converting atmospheric nitrogen gas (N 2 ) into ammonium ( NH + 4 ) and nitrate ( NO − 3 ), which are essential for many biological processes in the ocean. [ 22 ] As remineralization occurs, these microorganisms release phosphate, iron, and nitrate into the water column and their carbon-rich biomass sinks to deeper waters, contributing to the oceanic carbon cycle. [ 23 ]
A crucial factor for nitrogen fixers. Maintaining adequate levels of iron and phosphorus has been shown to be critical for microorganisms to carry out nitrogen fixation effectively. [ 22 ]
It serves as a vital energy source for photosynthetic nitrogen fixers, and insufficient intensity will reduce their ability to perform efficiently. [ 22 ]
The nitrogenase enzymes encoded in nitrogen fixers are highly sensitive to oxygen. [ 24 ] To overcome this challenge, some microorganisms have evolved adaptations to form specialized cells called heterocyst (create a low-oxygen environment) that allow nitrogen fixation to occur spatially different from the oxygen-producing photosynthesis processes. [ 25 ] [ 26 ]
When ocean temperatures rise, Trichodesmium populations tend to shift toward higher latitudes, potentially leading to a decline in their presence in tropical regions. [ 23 ] These changes could significantly affect nitrogen availability, global distribution of nitrogen-fixing species, [ 22 ] and disrupt overall ecosystem productivity across different oceanic regions. [ 23 ]
Seasonality plays a large role in the variability of all other factors. Fixation is lowest in the summer, particularly in coastal regions, [ 5 ] [ 14 ] due to the influence temperate summer conditions have on the process of upwelling . [ 13 ] [ 15 ] Upwelling is strongest in the summer months: April to August in the northern hemisphere and December to February in the southern hemisphere. [ 27 ] This flood of available nitrogen is complemented by blooms of photosynthetic species, so that cellular production is increased overall and DON (dissolved organic nitrogen) is greatly increased, reducing the need for fixation. [ 5 ]
There is a diverse range of marine species that contribute as nitrogen fixers to ensure a continuous supply of bioavailable nitrogen for primary production.
Trichodesmium is particularly important in nutrient-poor (sub)tropical surface waters; and, unlike many others, it does not form heterocysts. Instead, it uses alternative mechanisms to regulate oxygen levels during nitrogen fixation. [ 28 ]
UCYN-A is unique in that it lacks photosystem II , which allows it to fix nitrogen during the day while avoiding oxygen interference from photosynthesis. [ 28 ] In contrast, Crocosphaera watsonii has adapted to perform nitrogen fixation at night when oxygen levels are low, reducing the risk of nitrogenase inhibition. [ 29 ]
Organisms including Nodularia spp. and Anabaena spp. have developed heterocysts, which are thick-walled, structurally distinct cells that create an anaerobic environment necessary for nitrogenase enzyme in nitrogen fixers. [ 25 ] [ 30 ]
They contribute significantly to nitrogen fixation in oligotrophic regions. [ 22 ] For example, Richelia intracellularis is a heterocystous cyanobacterium that forms symbiotic relationships with diatom Hemiaulus hauckii . Diazotroph resides within the diatom's frustule , where it benefits from stable conditions and access to nutrients. In return, the diatom host receives a steady supply of nitrogen and therefore continues to thrive in nitrogen-depleted waters. [ 26 ] This partnership enhances nitrogen availability in marine ecosystems, promotes more diatom growth, and enables the biogeochemical cycling on a global scale.
Organisms form various symbiotic relationships, including mutualism , commensalism , and parasitism . [ 31 ] [ 32 ] Many symbiotic diazotrophs exhibit mutualism with the host cell, the benefit being receiving protein source and sufficient nutrients in return for supplying a biologically available form of nitrogen to the host. [ 33 ]
Cyanobacteria , the oldest known photosynthetic prokaryotes , form symbiotic relationships with various unicellular and multicellular organisms which exhibit diverse metabolic pathways, including diatoms , dinoflagellates and haptophytes . [ 34 ] [ 35 ] Unicellular and filamentous cyanobacteria are the main forms of cyanobacteria observed to have symbiotic relationships. [ 35 ]
Candidatus Atelocyanobacterium thalassa , otherwise called UCYN-A, is found to form close symbiosis with haptophyte algae, Braarudosphaera bigelowii , and their relationship is described as obligate endosymbiosis. [ 28 ] [ 25 ] [ 36 ] [ 37 ] Various nutrients, such as amino acids , purines , vitamins, and carbon sources in the form of glucose and glycerol-3-phosphate transferred from the host to UCYN-A, which is essential for its metabolic function and nitrogen assimilation. [ 28 ] In return, UCYN-A provides fixed nitrogen as ammonium , [ 25 ] ammonia , alanine , and glycine . [ 28 ] Additionally, reduced genome size, loss of genes for carbon uptake and photosynthesis, increase in gene expression for nitrogen fixation for UCYN-A, [ 36 ] [ 33 ] as well as a decrease in ammonium uptake by B. bigelowii [ 25 ] further represents the adaptation of both species to depend on this symbiotic relationship.
Richelia intracellularis is a filamentous cyanobacterial diazotroph [ 38 ] [ 39 ] that has endosymbiotic relationships with diatoms, described as diatom–dinotroph associations (DDAs). [ 40 ] [ 39 ] [ 41 ] Rhizosolenia and Hemiaulus [ 38 ] [ 39 ] are diatom species that have a close association with R. intracellularis . [ 40 ] [ 41 ] The domination of Hemiaulus - R. intracellularis symbiosis is seen in various pelagic systems, marking a greater contribution to the nitrogen and carbon fixation. [ 38 ] Evidence of obligate relationships could be seen from a positive correlation between nitrogen assimilation by R. intracellularis and photosynthesis by the host diatom, [ 38 ] [ 39 ] and successful growth of the host diatom without the addition of nitrogen in a laboratory setting. [ 39 ]
Filamentous heterocystous cyanobacterium, Calothrix spp. is also part of the DDAs, which form an ectosymbiotic relationship with diatoms, mainly Chaetoceros , attached to their spines. [ 42 ] [ 43 ] Neutral metabolism dependency was suggested through increasing nitrogen fixation rate compared to its free form [ 43 ] and growth restriction. [ 42 ]
Candidatus Tectiglobus diatomicola is classified under Rhizobia , a heterotrophic nitrogen-fixing proteobacterium symbiont that has an obligate endosymbiotic relationship with a pennate diatom Haslea . [ 44 ] Rhizobia has been known to have facultative endosymbiotic relationship with terrestrial legume. [ 45 ] The reduced genome size and low transcription of glycolysis-related genes of Ca. T. diatomicola suggest that it relies on Haslea on bypassing glycolysis. Haslea also relies on ammonium sources, as 99% of fixed nitrogen is transferred to Haslea . [ 44 ]
The evolutionary development of symbiotic relationships is found in many cellular mechanisms, such as chloroplasts in photosynthetic eukaryotes . [ 35 ] The gradual evolution of organelles from endosymbiotic relationships does not have a distinguishing point that indicates the difference. [ 46 ] Researchers use various criteria as indicators of organelle transformation, including genetic integration, cellular integration, and metabolic integration. [ 46 ] However, categorization becomes especially challenging when curtain endosymbiosis is in the process of transformation, as indicators of both endosymbiosis and organelle may coexist. [ 46 ] [ 47 ]
Due to the insufficient genetic integration and little to no endosymbiotic gene transfer (EGT) to the host diatom, diazoplasts could be classified as endosymbiotic symbionts. [ 48 ] [ 49 ] However, completion of high metabolic and cellular integration may be the indicator of organelle. Diazoplasts are found within the cells of the diatom Epithemia and are present in all species of this genus. [ 48 ] This constant existence of intercellular diazotroph, high degree of nutrient dependence on host, [ 48 ] and absence of regulation for nitroganase synthesis [ 49 ] may indicate the organelle-like function.
While some metabolic co-dependence between UCYN-A and Braarudosphaera bigelowii can be the evidence for both symbiosis and organelle, the level of genetic integration, generally assessed through the amount of genes transferred to the organelle and those lost from it, [ 46 ] is suggested by the significant portion of UCYN-A proteins that are encoded from B. bigelowii . [ 33 ] The cellular integration, including the close association of UCYN-A and other organelles in the B. bigelowii during cell division [ 33 ] and consistent size correlation of UCYN-A with B. bigelowii , also suggests the organelle function. [ 50 ]
Since 1850, the rate of anthropogenic reactive nitrogen deposition has doubled in oceanic systems, [ 51 ] driven by human activities such as agriculture, fossil fuel combustion, aquaculture , and household and industrial waste disposal. [ 52 ] Agriculture in the United States alone contributes about 11 million tonnes of nitrogen through the use of fertilisers. [ 53 ] Through agricultural runoff , this nitrogen seeps through soil into waterways and eventually reaches marine ecosystems. [ 54 ] Similarly, atmospheric nitrogen from fossil fuel combustion is deposited into water systems through precipitation or dry deposition, before being carried into the ocean by streams. [ 55 ] In aquaculture, dissolved nitrogen waste primarily comes from unused feed and fish waste. [ 56 ] Sewage, of which about 80% is left untreated, is sometimes disposed of directly into oceans. [ 57 ]
Excess nitrogen concentrations in marine ecosystems can lead to toxic algae blooms , a loss of biodiversity, marine dead zones and shellfish poisoning. [ 16 ] Toxic algae blooms occur when excess nitrogen and phosphorus allow algae and phytoplankton to grow uncontrollably on surface water. They rapidly consume oxygen and block sunlight from penetrating deeper water in a process called eutrophication . [ 58 ] As a result, the local biodiversity is greatly reduced, especially in bottom-dwelling species. This may lead to the formation of "dead zones", areas which have a dissolved oxygen concentration of less than 2 mL of O 2 /litre and thus cannot support marine life. Geological evidence suggests most dead zones today did not exist prior to anthropogenic nitrogen deposition, but rather studies show that their numbers have increased exponentially (doubled each decade) since the 1960s. [ 59 ] The Gulf of Mexico Dead Zone, in the northern Gulf of Mexico, is one of the world's largest hypoxic areas, [ 60 ] with excess nitrogen flowing in from the mouth of the Mississippi River . Although the Gulf of Mexico Dead Zone is considered seasonal, records indicate that since 1985 it continues to occur increasingly frequently and in larger areas, negatively impacting marine life and the many dependent fisheries. [ 61 ]
Surviving shellfish can become contaminated. As filter-feeders, they filter and absorb toxins produced by the phytoplankton associated with algal blooms. These toxins are difficult to eliminate, as they are not destroyed by cooking or freezing, and thus can cause severe disease in humans when ingested. [ 62 ]
Nitrogen pollution also affects tourism in areas dependent on boating and fishing activities. Each year the United States tourism industry loses an estimated US$1 billion due to nitrogen-induced algal blooms. [ 63 ]
Mitigation strategies to reduce marine anthropogenic nitrogen deposition vary depending on the source of pollution. To reduce agricultural runoff, practices such as the use of winter cover crops and perennial cropping systems have successfully mitigated nitrogen leakage. Most agricultural runoff occurs during winter and spring, when moisture levels drop and evapotranspiration rates decrease. [ 64 ] Winter cover crops protect soil during these seasons, and perennial crops such as alfalfa , allow stronger nitrogen retention. Growing these on agricultural land has reportedly resulted in 3 times and 30–50 times less nitrogen leaching, respectively. [ 33 ] Policy and educational measures to reduce excessive and unnecessary fertilisation have also been implemented. [ 33 ]
To reduce nitrogen pollution from human and industrial activities, the more widespread use of advanced denitrification wastewater plants is suggested. Currently, the cost of building and maintaining such facilities prevents the majority of wastewater produced globally from being adequately treated. [ 65 ] More efficient nitrogen removal and recovery processes are currently being developed to address this issue. [ 66 ]
Other mitigation strategies that have been implemented include the construction of artificial habitats and waterway rehabilitation. [ 33 ] Habitats such as wetlands and lagoons act as nitrogen sinks and prevent its constant seepage into the ocean. Similarly, waterways such as rivers and lakes can be rehabilitated to improve their nitrogen retention. They then act as buffers, reducing marine nitrogen fluxes. [ 33 ] | https://en.wikipedia.org/wiki/Marine_nitrogen_fixation |
A marine outfall (or ocean outfall ) is a pipeline or tunnel that discharges municipal or industrial wastewater , stormwater , combined sewer overflows (CSOs), cooling water , or brine effluents from water desalination plants to the sea. Usually they discharge under the sea's surface (submarine outfall). In the case of municipal wastewater, effluent is often being discharged after having undergone no or only primary treatment , with the intention of using the assimilative capacity of the sea for further treatment. Submarine outfalls are common throughout the world and probably number in the thousands. The light intensity and salinity in natural sea water disinfects the wastewater to ocean outfall system significantly. [ 1 ] More than 200 outfalls alone have been listed in a single international database maintained by the Institute for Hydromechanics at Karlsruhe University for the International Association of Hydraulic Engineering and Research (IAHR) / International Water Association (IWA) Committee on Marine Outfall Systems. [ 2 ]
The world's first marine outfall was built in Santa Monica , United States, in 1910. In Latin America and the Caribbean there were 134 outfalls with more than 500 m length in 2006 for wastewater disposal alone, according to a survey by the Pan American Center for Sanitary Engineering and Environmental Sciences (CEPIS) of PAHO . According to the survey, the largest number of municipal wastewater outfalls in the region exist in Venezuela (39), Chile (39) and Brazil (22). [ 2 ] The world's largest marine outfall stems from the Deer Island Waste Water Treatment Plant located in Boston , United States. [ 3 ] Currently, Boston has approximately 235 miles of combined sewers and 37 active CSO outfalls. Many outfalls are simply known by a public used name, e.g. Boston Outfall. [ 4 ] [ 5 ] [ 6 ] [ 7 ]
The main advantages of marine outfalls for the discharge of wastewater are: [ 8 ]
They also tend to be less expensive than advanced wastewater treatment plants, using the natural assimilative capacity of the sea instead of energy-intensive treatment processes in a plant. For example, preliminary treatment of wastewater is sufficient with an effective outfall and diffuser. The costs of preliminary treatment are about one tenth that of secondary treatment. [ 9 ] Preliminary treatment also requires much less land than advanced wastewater treatment.
Marine outfalls for partially treated or untreated wastewater remain controversial. The design calculation and computer models for pollution modeling have been criticized, arguing that dilution has been overemphasized and that other mechanisms work in the opposite direction, such as bioaccumulation of toxins , sedimentation of sludge particles and agglomeration of sewage particles with grease . Accumulative mechanisms include slick formation, windrow formation, flocculate formation and agglomerated formation. Grease or wax can interfere with dispersion, so that bacteria and viruses could be carried to remote locations where the concentration of bacterial predators would be low and the die-off rate much lower. [ 8 ] These theoretical concerns have been substantiated by real-world incidents, such as those detailed in the Controversies section of this article.
Outfalls vary in diameter from as narrow as 15 cm to as wide as 8 m; the widest registered outfall in the world with 8 m diameter is located in Navia (Spain) for the discharge of industrial wastewater. Outfalls vary in length from 50 m to 55 km, the longest registered outfalls being the Boston outfall with a length of 16 km and an industrial outfall in Ankleshwar (India) with a length of 55 km. The depth of the deepest point of an outfall varies from 3 m to up to 60 m, the deepest registered outfall being located in Macuto, Vargas (Venezuela) for the discharge of untreated municipal wastewater. [ citation needed ]
Outfall materials include polyethylene , stainless steel , carbon steel , glass-reinforced plastic , reinforced concrete , cast iron or tunnels through rock. Common installation methods for pipelines are float and sink, bottom pull and top pull. [ 2 ]
Submarine outfalls exist, existed or have been considered in the following locations, among many others:
In the 1960s the city of Sydney decided to build ocean sewage outfalls to discharge partially treated sewage 2–4 km offshore at a cost of US$300 million. In the late 1980s, however, the government promised to upgrade the coastal treatment plants so that sewage would be treated to at least secondary treatment standards before discharge into the ocean. [ 16 ]
Despite these promises, as of 2024, Sydney's major outfalls at Bondi and Malabar were still providing only primary treatment before discharge. In October 2024, the problems with this approach became evident when thousands of tennis ball-sized "grime balls" washed ashore on Sydney beaches, forcing their closure. Scientific analysis revealed these spheres contained a mixture of cooking oil, soap scum, fecal matter, and various contaminants. An investigation by New South Wales environmental authorities determined that Sydney Water's aging sewerage network and its ocean outfalls were the likely source, with the debris matching samples from the treatment facilities that discharge sewage effluent offshore after only primary treatment. This incident demonstrated how fats, oils, and greases in wastewater systems can agglomerate into pollution that impacts coastal areas despite offshore discharge, renewing calls for the long-promised secondary treatment upgrades. [ 17 ]
The submarine outfall in Cartagena, Colombia was financed with a loan by the World Bank . It was subsequently challenged by residents claiming that the wastewater caused damage to the marine environment and to fisheries. The case was taken up by the World Bank's Inspection Panel , which contracted two independent three-dimensional modeling efforts in 2006. Both "confirmed that the 2.85km long submarine outfall (was) adequate." [ 18 ]
For disposal into the ocean, environmental treaty requirements have to met. As international treaties often manage water over countries' borders, wastewater disposal is easier in bodies of water found entirely under the jurisdiction of one country. [ citation needed ] | https://en.wikipedia.org/wiki/Marine_outfall |
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