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to be addressed with specific remedies to restore coastal wetlands. |
Sea-level rise has to be considered in wetland restoration. For one, it influences the location of the ecotone between the mangrove and herbaceous wetland |
and the boundary of the white zone, and sea-level rise |
might shift them inland over coming decades. For another, hydrostatic pressure from increased sea level |
might further retard ground-water inflows already diminished by a lowered water table. |
Benthic Communities |
Relationship of Bottom Habitat to Freshwater Inflow |
Volume and Variation. Benthic communities are related to stressors as depicted in the third diamond of |
Figure 2. Benthic communities are directly impacted |
by the volume and intensity of freshwater inflow and |
the range and rapidity of its variation. Point-source |
discharges of fresh water into the bay via conveyance |
canals result in large, but ephemeral, salinity fluctuations that deleteriously affect benthic communities |
(Montague and Ley 1993, Irlandi et al. 1997). The bay |
bottom in the vicinity of canals often is devoid of benthic organisms. Miami-Dade Department of Environmental Resources Management documented destruction of established benthic sessile communities in |
Manatee Bay in the extreme south Biscayne Bay by |
sudden and prolonged high-volume releases of fresh |
water. Recovery is dependent upon the duration of appropriate salinity regimes between events. Benthic |
communities are also directly affected by trawling, |
which can significantly disturb bottom habitat and benthic organisms. |
Pink Shrimp |
Pink shrimp are related to stressors primarily |
through diamonds 2 and 3 in Figure 2. These relate |
suitability of habitat for pink shrimp to salinity pattern |
and water quality and catches in the fishery to abundance of juvenile pink shrimp. |
Relationship of Suitable Pink Shrimp Habitat to Salinity Pattern and Water Quality. Changes in water |
management in relation to CERP are expected to expand the area of optimal habitat for juvenile pink |
shrimp both directly and indirectly. Salinity, which affects many physiological processes, is a major environmental factor directly influencing pink shrimp. Like |
many species, pink shrimp have an optimum salinity |
range (Browder et al. 2002). Although the species may |
be found outside of this range, survival, growth, and |
reproduction may not be as great. As for many species, |
optimum salinity for shrimp must occur in conjunction |
with suitable bottom habitat (e.g., seagrass) to be supportive, and salinity patterns and water quality will |
directly affect seagrass distribution, composition and |
density, thus affecting shrimp indirectly (Browder et |
al. 2005). |
Relationship of Juvenile Pink Shrimp to Shrimp Harvests. High densities of juvenile pink shrimp can be |
expected to enable high catch rates in fisheries. A close |
link between juvenile densities and catch rates in bay |
shrimp fisheries would be expected because nursery |
and fishing grounds overlap or are in close proximity. |
EXHIBIT 7 |
Browder et al., Biscayne Bay CEM 865 |
Fishing effort may affect juvenile density on fishing |
grounds, but trawls cannot operate in waters less than |
one meter deep, where the nursery grounds in Biscayne Bay are located (Diaz 2001). The relationship |
of pink shrimp juveniles in Biscayne Bay to offshore |
spawning or fishing grounds is unknown. The nearest |
known spawning and fishing grounds are near the Dry |
Tortugas, and the relationship between the spawning |
grounds and the Biscayne Bay nursery has not been |
determined. |
Estuarine Fish Community |
Relationship of Estuarine Fish Communities to Salinity |
Pattern. The estuarine fish community is related to |
stressors through diamonds 2 and 3 in Figure 2. Abundance and biomass of estuarine fishes has been reduced and species diversity has changed due to a loss |
of estuarine habitat along the bay’s western shoreline |
(Serafy et al. 2001). Much of this habitat loss stems |
from changes in freshwater inflow that have disturbed |
the natural correspondence of favorable salinity with |
favorable bottom and shoreline habitat for estuarine |
species (Browder and Moore 1981). These species |
need a persistent positive salinity gradient extending |
from coastal wetlands, freshwater coastal creeks, and |
shallow nearshore waters into the bay. Flow from canals rather than through coastal wetlands prevents development of a positive gradient from interior wetlands into the bay. Unnaturally high salinity fluctuations caused by canal discharges further reduce suitable habitat for estuarine fish communities (Serafy et |
al. 1997). Presently, the rate of freshwater inflow fluctuates in a much more pronounced way than it did |
prior to the construction of the water-management system. Fluctuation is because of the shortage of storage |
for stormwater runoff in the watershed and manipulation of the little storage that exists. For example, at |
the end of wet season and during dry season (generally |
November to May), water may be discharged to artificially maintain low ground-water elevations in the |
watershed to promote agricultural activity, even |
though no rainfall has occurred; contrarily, sometimes |
no water is discharged after storm events because water stages are still below optimum. Spatial and temporal patterns of freshwater delivery that radically depart from the natural pattern of flow in relation to rainfall do not provide optimal habitat for estuarine species. Many species that can withstand gradual changes |
in salinity are vulnerable to the abrupt lowering of |
salinity caused by freshwater pulses (Serafy et al. |
1997). |
Fish and Bottlenose Dolphin Health |
Contaminants present in Biscayne Bay’s sediments |
and water column at various locations, including the |
Miami River mouth, may affect faunal health and development in the bay. Fish and bottlenose dolphin |
were selected to help monitor potential adverse effects |
of contaminants because a relatively high prevalence |
of morphological abnormalities has been found in fish |
from some locations in Biscayne Bay, and bottlenose |
dolphin are a long-lived species in which contaminants |
are known to accumulate, according to studies in other |
estuaries. Fish and dolphin health are related to stressors through diamond 1 in Figure 2. |
Relationship of Fish Abnormalities to Human Influences. The relationship between exposure to anthropogenic inputs and morphological abnormalities observed in Biscayne Bay fishes needs evaluation in view |
of the higher prevalence of fish with abnormalities in |
areas of the bay directly exposed to human inputs. The |
most common abnormalities in Biscayne Bay fish are |
scale disorientation and deformed or missing dorsal fin |
spines, which are found in a number of species (Browder et al. 1993). Limited data from selected locations |
showed significant correlations between combined abnormalities and aliphatic hydrocarbons in sediments |
and between abnormalities in bluestriped grunt (Haemulon sciurus Shaw) and copper in sediments (although not with other sediment contaminants) (Gassman et al. 1994). Other factors can also influence fish |
health and development, including, according to some |
reports, previous encounters with fishing gear. |
Relationship of Bottlenose Dolphin Toxicant Body |
Burden to Toxicants in the Sediments. The body burden of toxicants in the Biscayne Bay resident bottlenose dolphin population may reflect their degree of |
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