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shoalgrass as a species more characteristic of variable salinities, no simultaneous
fauna data was gathered. Therefore, the data from this ongoing study should
provide a more definitive answer to the question about what salinity over what
habitat type results in a greater catch of specific species. Until that is known, it is
very difficult to define species/salinity/habitat relationships for this sub-area of
the Bay.
Given these uncertainties, the recommended contingency option is to maintain
all the existing flows into this sub-area of the Bay until such time as additional
scientific information on the specific freshwater flows and levels for the above
mentioned suite of species, or additional species occurring in this location, are
Recommendation of Preferred Approaches
Freshwater Flow and Ecological Relationships in Biscayne Bay 6-6
scientifically documented, a revised and more scientifically based freshwater
flow plan can be studied.
SOUTH-CENTRAL BISCAYNE BAY
The recommended approach rated highest at 22 with a range of values from 5-22.
The approach is the Valued Ecosystem Component approach, with the VEC a
sustainable pink shrimp harvest (Table E-5).
The scientific information data support for this option is rated as a 2 on a scale of
0-5 (Table 6).
South Central Biscayne Bay shares many of the same characteristics as Central
Biscayne Bay except that all of this area is within Biscayne National Park, it has
less dense seagrass area, and more hardbottom mixed with seagrass. Robblee et
al. (2001) note that the work of Diaz (2001) indicates that pink shrimp abundance
north of Black Point is greater than that found south of Black Point possibly
indicating some major difference in seagrass and/or salinity regimes in the two
areas. The discussion above about the Biscayne Bay Coastal Biological
Community Performance Measures Project and associated narratives applies
here as well as sampling is taking place in both areas.
Given the similar uncertainties found in Central Biscayne Bay, the recommended
contingency option is similar, to maintain all the existing flows into this sub-area
of the Bay until such time that additional scientific information on the specific
freshwater flows and levels for the above mentioned suite of species, or
additional species occurring in this location, are scientifically documented, and a
revised and more scientifically based freshwater plan can be studied.
SOUTHERN BISCAYNE BAY
The recommended approach rated highest at 26 with a range of values from 5-26
(Table E-6). The approach is the Food Web Support approach, with the intent
that the forage fish food base for both the Roseate spoonbill (and several other
wading bird species) and the American crocodile would be the target reference
point.
The scientific information data support for this option is rated as a 4 on a scale of
0-5 (Table 6).
This high rating is based upon the detailed studies reported in Lorenz et al.
(2002) and Mazzotti and Cherkiss (1998). Unlike the other areas of the Bay, the
problems of historic freshwater input modifications to this area have been looked
Recommendation of Preferred Approaches
Freshwater Flow and Ecological Relationships in Biscayne Bay 6-7
at in more detail related to the C-111 canal which enters the most southerly
portion of this area at Manatee Bay (Bellmund et al. 1999). Lorenz (pers. comm.)
has recently been made aware of significant Roseate spoonbill use of the
wetlands west of Turkey Point and is of the professional opinion that restoring
freshwater flows to this area could have significant positive benefits to the
Roseate spoonbill, associated wading bird species, and the American crocodile.
This is due to a similar biological response described in Bellmund et al. (1999),
Lorenz (1999), Lorenz (2000) and Lorenz et al. (2002). This response is an increase
in the small demersal fish (i.e., Cyprinodon variegatus and Poecilia latipinna) and
benthic epifaunal shrimp of the genus Palaemonetes “…found in virtually every
analysis of spoonbill diet…” as a result of lower salinities, and reduced variation
in overall salinities within brackish marsh and scrub mangrove habitat typical of
the landward zone behind a narrow fringe of mangroves. These same food items
are also important for subadult crocodiles (USFWS 1999) which also respond
favorably to reduced salinity stress. Bellmund et al. (1999) referred to the
response as the production of “high fish biomass” (p. 9). Lorenz et al. (2002)
stated that “…the biomass of the prey base is impacted by hydrographic
conditions: specifically, fish production is related to the salinity regime such that
increased freshwater flow is correlated with increased prey-base fish stock…” (p.
601).
It is likely that the current conditions in this sub-area of the Bay result in some
reduction to this “prey-base fish stock”, and to increased salinities impacting
survival of juvenile American crocodiles. Until these potential impacts can be
better quantified, the contingency alternative should be to maintain the existing
fresh water flows.
Information Deficiencies and Needs
Freshwater Flow and Ecological Relationships in Biscayne Bay 7-1
SECTION 7
INFORMATION DEFICIENCIES AND NEEDS
In conducting the literature search, interviewing experts and analyzing the
information that is available concerning historical and existing conditions in
Biscayne Bay, the project team has identified a number of areas in which
additional information would be extremely valuable in developing and/or
refining MFL rules and thresholds. In many cases, such as analysis of oyster
populations, surveys and/or mapping has been done only in portions of the Bay.
Having and analyzing the results of a bay-wide mapping effort of this estuarinedependant species would be extremely valuable in understanding existing
salinity regimes and in identifying conditions that could prevent significant
harm. A preliminary list of data needs includes:
1) Actual locations of oyster bars and seagrass in and around Oleta River Park
need to be confirmed and mapped.
2) Current and historical water quality data needs to be synthesized to
determine what the seasonal salinity regimes are, particularly in the
western inshore (and canal) areas of Central, South-Central and Southern
Bay. If data are lacking, a water quality sampling program needs to be
instituted. Probably ten year minimum sampling on a monthly basis at a
network of 25 stations.
3) For the same locations above, detailed maps of live and fossil or recent
historical American oyster and other oyster species, and seagrass (from D.
Mir-Gonzalez study), and fresh and saltwater wetlands need to be mapped
very accurately. Results from research presently being conducted (e.g., FIU
graduate student D. Mir-Gonzalez) should be obtained and analyzed, and
any adjustments/modifications to the MFL process that may be warranted