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Recommendation of Preferred Approaches
Freshwater Flow and Ecological Relationships in Biscayne Bay 6-3
OLETA RIVER/SNAKE CREEK
The recommended approach rated highest at 22 with a range of values from 6-22.
The approach is the Indicator Species approach, with the indicator species being
the American oyster, West Indian manatee and Johnson's seagrass (Table E-1).
The scientific data to support for using this approach is rated 2 on a scale of 0 to
5, where 0 is pure conjecture with no data support, 3 is moderate data support,
and 5 is very strong data support (Table 6).
While we know oysters are present (FDEP 2002), there is no definitive mapping
of the existing oyster resources in this area, and the health of the oysters is
unknown. Therefore it is not possible to say it maintaining the existing water
flows and levels will protect this resource. We know manatees use this area
(DERM 1995), but whether the existing water flows are optimum or suboptimum for manatee protection is unknown. We know Johnson’s seagrass is
present in the park (FDEP 2002), but this species is only described in the
Johnson’s seagrass recovery plan as being euryhaline and found in a salinity
range of 15-43 psu, “…but has been observed growing perennially near the
mouths of freshwater discharge canals…” (page 1.2-3 in NMFS 2002). Again,
whether flows are optimum or not in this area is unknown.
Given these uncertainties, the recommended contingency option is to maintain
all the existing flows through wetlands and into the Bay in this area until
additional scientific information on the specific freshwater flows and levels for
these, or additional species occurring in this location, are scientifically
documented.
NORTHERN BISCAYNE BAY
The recommended approach rated highest at 22 with a range of values from 6-22.
The approach is the Indicator Species approach, with the indicator species being
the spotted seatrout and manatee grass (Table E-2).
The scientific information data support for this option is rated as a 3 on a scale of
0-5 (Table 6).
The moderate level of information available is reflected in the reported capture of
96% of all seatrout from one study (Serafy et al. 1997) north of Rickenbacker
Causeway, and 68% in this portion of the Bay. Bellmund et al. (1999)(page 7)
confirm the use of this species with the statement that “…In North Biscayne Bay
Recommendation of Preferred Approaches
Freshwater Flow and Ecological Relationships in Biscayne Bay 6-4
sea trout spawning is believed to be linked to the presence of stable low salinity
areas which are available seasonally…”
The dominant species within seagrass beds in this area is manatee grass. This
species also appears to grow best in stable salinity fluctuation areas, but data to
support the existing freshwater flows as being protective of these seagrass beds
is lacking. Fourqueran (pers. comm..) feels its tolerance of lower light levels than
other species of seagrass may be the cause of its persistence and perhaps
competitive advantage at this location, rather than a tolerance of lower salinities
than other seagrass species.
Given these uncertainties, the recommended contingency option is to maintain
all the existing flows into this sub-area of the Bay until additional scientific
information on the specific freshwater flows and levels for these, or additional
species occurring in this location, are scientifically documented.
MIAMI RIVER/GOVERNMENT CUT
The recommended approach rated highest at 20 with a range of values from 5-20.
The approach is the Community Index approach, intended to utilize a
biodiversity index similar to that developed by Berkely and Campos (1984) for
the Bay (Table E-3)
The scientific information data support for this option is rated as a 2 on a scale of
0-5 (Table 6).
We have been able to find very little specific information on indicator species for
this area of the Bay. Alleman (pers. comm.) notes that this part of the bay was
reported by Serafy et al. (1997) to have the highest fish species diversity of all the
sampled stations. The Miami River is known to have highly polluted bottom
sediments that are now the subject of a maintenance dredging project, but the
existing water flows likely maintain a complete gradient from freshwater in its
upper reaches, to euhaline at the entrance to the port. This range of salinities
overlaps a wide variety of bottom communities, and may be the reason for such a
high diversity of fish and possibly also invertebrates.
Given these uncertainties, the recommended contingency option is to maintain
all the existing flows into this sub-area of the Bay until additional scientific
information on the specific freshwater flows and levels for these, or additional
species occurring in this location, are scientifically documented.
Recommendation of Preferred Approaches
Freshwater Flow and Ecological Relationships in Biscayne Bay 6-5
CENTRAL BISCAYNE BAY
The recommended approach rated highest at 22 with a range of values from 5-22.
Both the Indicator Species approach and the Valued Ecosystem Component
approach scored the same (Table E-4). The Indicator Species approach was
judged the better of the two by the principal scientists, and the species chosen
were being the pink shrimp and shoalgrass. Benthic infaunal and epifaunal
invertebrate communities were not chosen as good indicators due to the
multiparameter responses that are not directly connected with salinity changes in
this sub-area of the Bay (Graves et al. 2003).
The scientific information data support for this option is rated as a 2 on a scale of
0-5 (Table 6).
This level of uncertainty is supported by the following quotes from the proposal
(currently funded) for the “Biscayne Bay Coastal Biological Community
Performance Measures Project” (Browder 2001): “…major water management
initiatives will influence the quantity, timing and quality of freshwater inflow to
Biscayne Bay…” however “…Biscayne Bay is handicapped by lack of
information about conditions and communities in the western nearshore
Bay…The benthic animal community, consisting of small forage fish, juvenile
game fish, and invertebrates such as pink shrimp…blue crab…gray snapper…are
linked to nearshore environments, but their relationships with freshwater inflow
have received little investigative attention in Biscayne Bay.” The data for the first
year of this sampling are expected to be available in nine months, and a second
year of sampling is proposed.
The study plan for the above reference study (Robblee et al. 2001) stated that the
dominant vegetation type(s) for the sampling areas will be measured and
reported along with the invertebrate and fish collected. Water quality data will
be collected using hydrolabs. Although Fourqueran et al. (2003) characterized