Datasets:
patrickbdevaney
/
mia9

Dataset card Data Studio Files
xet
 Community
1
text
stringlengths
0
6.44k
of its hydrology and also sustained urban and agricultural development. Nevertheless,
Biscayne Bay remains very productive and its biodiversity is noteworthy. Its waters
nurture 800 species including 150 species of shrimp, crabs, sponges and lobsters, 512
tropical and temperate fish species, and prolific benthic communities dominated by
seagrass meadows. Furthermore, its shorelines and intertidal areas are major stopover
of migrating shorebirds where manatees, dolphins, alligator and crocodiles, also thrive.
To protect these valuable resources, the U. S. Congress designated 69,605 hectares
(172,000 acres) of central and southern Biscayne Bay, at the southeastern tip of the
Florida Peninsula, as Biscayne National Park (BNP) in 1982. As such, BNP became the
largest marine park in the U.S. national park system. The Park is bounded by protected
areas on the south and east by the Florida Keys National Marine Sanctuary and on the
north by the extension of the Biscayne Bay Aquatic Preserve, but its western boundary
is with the Miami City metropolitan area, where sprawl growth and resource demands
pose serious threats to the park integrity and to its natural resources.
The main objectives of this project are: first, to develop an understanding of
nutrient inflows into Biscayne Bay, their effects on the bay’s water, and to evaluate the
ecological impacts on Biscayne National Park’s resources associated with Miami’s
future population growth and land use changes; and second, the derivation of protective
numeric nutrient criteria (NNC) for South Florida estuarine and coastal waters. Several
institutions have implemented water quality (WQ) monitoring for over two decades in
South Florida. We have selected Florida International University’s database as a
reference dataset given its spatial-temporal coverage at fixed 353 stations,
iv
completeness of measured variables (over 725,000 WQ measurements) and its
sustained field and analytical protocols along the period of record. Other available
databases would be used for comparison and verification purposes.
Although Biscayne Bay waters are in general oligotrophic, water composition is
not uniform across the bay, and responds to magnitude and type of intervention. North
Bay, the most affected by urban development, is the highest in total phosphorous, and
chlorpphyll-a (CHLa) concentration, and relatively high silica (SiO2), inorganic nitrogen
and turbidity, while oceanic waters on the reef-track display the lowest nutrient
concentrations. North-central bay, impacted by urban and industrial development,
shows values which are intermediate for all variables, while South-central bay, impacted
by agricultural activities and urban development in its watershed, has the lowest CHLa,
SiO2 and turbidity, and highest inorganic nitrogen concentrations. Finally, South
Biscayne Bay, surrounded by wetlands and practically devoid of urban development in
its watershed, has the lowest salinity and highest total nitrogen (TN), total organic
nitrogen (TON) and total organic carbon (TOC).
We calculated descriptive statistics and performed long-term trend exploration of
the time-series, to gain insight into patterns of behavior along the period of record
(POR) for all relevant biogeochemical parameters. This exploration was performed with
Akritas-Theil Sen and Z-score cumulative sum charts (Z-CUSUM) methodologies. The
spatial-temporal variability within estuaries and coastal waters in individual South
Florida basins called for a holistic approach to basin segmentation to account for
variability not only dictated by a given nutrient concentration level, but by the
combination of stressors conditions (nutrients, water clarity, climate, weather, extreme
events, geomorphology, circulation and exchange, management, etc.). Basin
segmentation was accomplished with an objective classification of station combining
Principal Component Analysis (PCA) and Hierarchical Clustering methods in tandem.
Besides statistics, spatial extension and pattern, geomorphology, water circulation and
benthic ecosystem distribution played a major role on the final delineation of 40
segments extending from Biscayne Bay in the east to Dry Tortugas in the southwest
v
and to Pine Island Sound in the northwest. This segmentation, or a modification of it,
has been adopted by both, EPA and FDEP as fundamental framework for the derivation
of numeric nutrient criteria for South Florida estuaries and coastal waters.
Substantial changes and climate-driven regime shifts have been documented for
water quality in South Florida. The most relevant changes we identified in Biscayne Bay
were those occurring in the early-to-mid nineties from lower to higher precipitation rates,
leading in turn to a generalized region-wide decline in water nutrients and chlorophyll a
(CHL-a) concentrations (Briceño and Boyer 2010). Based upon a detailed literature
review and a recent assessment of natural resource conditions in Biscayne Bay and
BNP natural resources (Harlem et al. 2009), we evaluated threats and stressors on
water resources of BNP attempting to improve understanding of its resources, in order
to inform management of the identified threats directly related to human impacts.
Given the oligotrophic nature of its waters, South Florida’s ecosystems respond
very rapidly to small nutrient enrichment, especially to increases of phosphorous, the
limiting nutrient. Biscayne Bay watershed displays diverse agricultural, urban and
wetland cover, leading to differences in freshwater characteristics as well as in bay
water composition. Median NOx concentrations are higher in agricultural runoff than in
urban or wetland runoff; median concentrations of ammonia, TP, and SRP tend to be
higher in urban runoff than in wetland or agricultural runoff; and median TON
concentrations are higher in wetland and urban runoff than in agricultural runoff.
Legacy and current-use pesticides, herbicides and their metabolites have been
consistently detected, often at low concentrations, in canals and near-shore locations.
Metals display little spatial difference except for lower values near Fisher Island and
relatively high concentrations in sediments near the mouth of the Miami River. Also,
some heavy metals are highest near marinas, where antifouling compounds were also
high. Polychlorinated biphenyls (PCBs) are present in the highest concentrations and 5
times higher in male dolphins with sighting histories in the northern, metropolitan area of
Biscayne Bay than to the south. Polynuclear aromatic hydrocarbons (PAHs) are
vi
commonly present in sediment samples, at relatively low concentrations with higher
values occurring in marinas.
Climate change threats to Biscayne National Park resources are linked to
changes in rainfall and evaporation patterns affecting the amount of available
freshwater and potentially causing prolonged droughts and/or flooding; saltwater
intrusion into the coastal aquifers and public water supply wells; reduction of coastal
stormwater release capacity due to sea level rise; and changes in tropical storm and
hurricane activity with increased surge levels. One aspect of great concern is the
release of sediment and its associated nutrients and pollutants to the marine system as
coastlines erode due to sea level rise and storm activity.
The Florida Department of Environmental Protection (FDEP) and the US
Environmental Protection Agency (EPA) are in the process of developing numerical
nutrient criteria for estuaries and coastal marine waters for Florida. Given the scarcity
of information on the estuarine effects of nutrient enrichment on South Florida
ecosystem components and the well documented relationship between nutrients and
CHL-a, we approached the derivation of nutrient (Total Nitrogen and Phosphorus)
concentration thresholds for each segment by identifying those concentrations above
which significant increases in CHL-a occur. For this purpose we calculated and plotted