Datasets:
patrickbdevaney
/
mia9

Dataset card Data Studio Files
xet
 Community
1
text
stringlengths
0
6.44k
oyster bars were found “…buried by only a few centimeters to decimeters of
sediment.” No live oysters were reported observed. Meeder et al. (1997) also
notes that “No extensive fossil oyster bars have been located…” in South
Biscayne Bay.
Meeder et al. (1999), reports that no live oyster reefs, but nine historic reefs were
found in a survey of 48 tidal creeks between the Coral Gables Canal and Mowry
Canal, but that “oysters were seasonally abundant…” and “coon oysters (those
that live on mangrove prop roots) were much more abundant.” These may not be
the American oyster, but are likely one of three other species of oysters that are
found associated with mangroves; Ostrea (Lopha) frons, Crassostrea rhizophorae and
Isognomon alatus (Britton and Morton 1989). Meeder (pers. comm.) has confirmed
recent observations of submerged live American oysters in this same vicinity.
Healthy oyster bars are typically found in brackish water where salinities
routinely drop below 15 psu. This provides protection from less euryhaline
predators such as predatory gastropods and starfish. Changes in freshwater
flows to Biscayne Bay (see above under “Mangrove Forests”) have altered
conditions that historically were more favorable to oyster reef formation and
persistence.
Restoration of oyster reefs has been proposed as an indicator of successful
management of freshwater flows to Biscayne Bay (Meeder 2001).
Hardbottom
Hardbottom refers to exposed rock or limestone where there are attached algae
(Halimeda spp, Penicillus spp., Rhipocephalus spp., and Udotea spp.), sponges
(Hippospongia lachne, Spongia barbara, S. germinea, S. cheiris), hard corals (Porites
sp., Solenastrea sp. Siderastrea), fire coral (Millepora sp.) and/or soft corals (Eunicea
spp., Plexaurella dichotoma and Pseudopterogorgia spp.) (Milano 1983).
Valued Ecosystem Components
Freshwater Flow and Ecological Relationships in Biscayne Bay 4-5
Softbottom
Alleman et al. (1995) state that a benthic survey by Schroeder (1984) resulted in
documentation of over 800 species of invertebrates. For softbottom habitats
generally devoid of submerged aquatic vegetation and attached algae or
invertebrates, the predominant organisms are epibenthic or infaunal
invertebrates and some benthic fish like the toadfish, Opsanus beta. It is reported
that Milano (1983) determined that 14% of Biscayne Bay was bare or softbottom
habitat, supporting polycheate worms, molluscs (clams and snails), tunicates,
nematodes, crabs, shrimp, amphipods and echinoderms, including sea
cucumbers.
POTENTIAL INDICATOR SPECIES
The task of identifying individual species or suites of species that would serve as
good indicators of ecosystem health is a challenging endeavor that must take into
account a variety of inter-related factors, including:
· The existing spatial distribution and abundance of the organism;
· The salinity tolerance range of the species;
· The degree to which non-salinity water quality parameters could affect
changes in the presence/absence and spatial distribution of the species;
· The extent to which changes in the species presence/absence over time could
be determined to be based primarily on changes in salinity regime; and
· The extent to which impacts to the species that might result from changes in
fresh water flows could result in enforcement actions by local, state and/or
federal governmental agencies (i.e., impacts to listed species)..
Based on these criteria, a number of species and/or ecological communities have
been identified as potential indicators for Biscayne Bay. Each species, or group
of species is identified and described in the remainder of this section.
Micro-organisms
Several groups of micro-organisms have been analyzed for their potential utility
as indicators of environmental health in Biscayne Bay. The groups that are
analyzed in this sub-section include foraminiferans, phytoplankton and benthic
diatoms.
Formaniferans
Foraminiferans (forams), tiny protozoans of the Order Foraminifera, are
present in fairly large numbers on the surface of sediments in tidal waters.
Valued Ecosystem Components
Freshwater Flow and Ecological Relationships in Biscayne Bay 4-6
They are chiefly marine rhizopods that typically have calcareous shells that
are often perforated with minute holes through which protrude slender
pseudopodia. Although many species are comparatively minute, some
exceed 3-5 cm in total length when various spines and ridges are included.
Some forams cement sand grains and shell fragments that are gathered from
the surface of the sediments, others secrete calcium carbonate. These
organisms are a major component of the limestone sediments in tidal areas.
They consume unicellular algae, algal spores, bacteria, other micro-organisms
such as copepods, ciliates and worms, and organic debris.
Fossil forams are particularly useful in identifying and interpreting historical
sediment conditions, due to their overall widespread abundance and
occurrence and their ‘convenient‘ size; sufficiently small to be recovered
intact and an in large numbers, yet not so small that they cannot be easily
examined, identified and counted.
Life spans vary from species to species and generally range from a period of a
week or so to several months. Different species have differing sensitivities to
certain water quality parameters, and salinity is a key factor in determining
the presence/absence of some species.
Analyses of core samples taken at 23 sites located throughout Biscayne Bay
during 1996 revealed the presence of 69 foram taxa (Ishman et. al., 1997).
Two foram species (Ammonia parkinsoniana tepida and Elphidium galvestonense
mexicanum) appear to have such similar water quality requirements that they
often occur in close enough proximity to one another and have been
characterized as constituting an Ammonia-Elphidium assemblage (Ishman et.
al., 1997). These species presently exist in western areas of Biscayne Bay, and
could serve as potential indicators of maintenance of desirable salinity
regimes (S. Ishman, pers. comm.). Based on various characteristics, including
their: a) life cycles, b) relatively narrow salinity tolerance range; c) high
tolerance of non-salinity water quality parameters (e.g., elevated nutrients);
d) relative abundance; and e) comparatively fast response time, the presence,
absence and/or abundance of these species could be an excellent gauge of the
extent to which reductions in freshwater flow (and the resulting changes in
salinity) are causing harm or significant harm in Biscayne Bay.
On-going studies by Ishman have led to the identification of four benthic
foraminiferan assemblages in surficial sediment samples collected in Biscayne
Bay. One such assemblage, a “restricted environmental assemblage” is