Alterations in endocrine function and reproductive success have been documented among largemouth bass in Central Florida as a potential response to environmental contaminants. These data suggest that exposure to site-specific sources, primarily agricultural sites and pesticides, may be responsible for these toxicities. The assessment of exposures for largemouth bass within the Greater Everglades ecosystem is an essential component of current and future assessments of risks and potential effects of proposed and ongoing restoration. To enable an assessment of contaminant risks for the Greater Everglades Ecosystems it is critical that an initial, complete food-chain, characterization of contaminants be conducted. These results would form the critical basis of any initial risk assessment and are necessary for any evaluation and (or) assessment of risk that may be related to restoration of the Greater Everglades Ecosystem. In addition, these results would form the basis of any future evaluations of adverse effects, paired field and laboratory studies, and the critical assessments or evaluations of restoration success or resultant adverse effects.

The current study evaluated contaminant exposures and potential physiological effects for largemouth bass in the Greater Everglades ecosystem. Largemouth bass were collected and sacrificed from several specific sites involved in future restoration efforts (32 sites, n=20 per site, over 750 samples): Everglades NP, Loxahatchee NWR, Big Cypress NP, Canals including C111, L39, L5, U3, S5A, G3, Holyland; STA’s 1, 2, 3, 4, 5 and 6; Water Conservation Areas 2A, 3A-N, and 3A-S. Several tissues were collected for contaminant analysis: blood, liver, muscle, and gonad. Contaminant analyses will include an assessment of chlorinated hydrocarbons (i.e. pesticides, PCB’s, PAH’s), water-soluble herbicides, organophosphates, carbamates, and metals (i.e. mercury, lead, selenium, etc.). Blood was utilized for blood chemistry assessments of health status and endocrine status (sex steroids and thyroid function). Gonadal and liver tissues were examined histologically for an evaluation of reproductive status and liver toxicity. Sex was identified as follows: the presence of ovarian tissue and absence of testicular tissue = female; presence of testes and absence of ovarian tissue = normal male; and presence of testes with ovarian tissue = intersex . Selected samples from several fish were composited to assess the appropriate tissues for each contaminant analysis. Samples collected during 1999 (approx. 5 animals per site) were also composited and analyzed for selected contaminants (persistent pesticides and several current use pesticides). Plasma was analyzed for biomarkers of reproductive status (estradiol and testosterone) and metabolism/thryroid function (T3 and T4).

Results of the preliminary phase of this project indicated a differential tissue distribution for each class of contaminant. Lipid soluble pesticides (i.e. chlorinated hydrocarbons) were detectable in all tissues examined except blood. Blood concentrations of the chlorinated hydrocarbon pesticides were, in general, below detection limits. In contrast, analyses of water-soluble pesticides (i.e. current use pesticides), organophosphates and carbamates were routinely detected in blood and tissues at similar levels. Muscle tissue (i.e. fillets) was chosen for the focus of these preliminary analyses for the organochlorine pesticides, while blood plasma was utilized for the other pesticide contaminants. Initial analyses were conducted on a composite of five fish from each site and preliminary results are summarized in figures 1 and 2.

Figure 1. Preliminary analysis of chlorinated hydrocarbon pesticides for muscle tissue from largemouth bass across several broad regions of the Greater Everglades ecosystem. Results are as ppb for wet weight of tissue. Lipid concentrations did not differ between sites. [larger image]

Figure 2. Preliminary analysis of plasma atrazine and incidence of intersex for sites throughout the Greater Everglades ecosystem. Atrazine data is listed as ppb. Note low background level of intersex for all sites and increased incidence of STA’s 2, 4, 5 and 6. [larger image]

Results indicate site-specific patterns of contaminant exposure for fish in the Greater Everglades ecosystem, and the potential for endocrine system and reproductive effects. These data demonstrate the need for a thorough assessment of exposures for wildlife within the Greater Everglades ecosystem as an essential component of current and future assessments of risks and the potential effects of proposed and ongoing restoration.

Contact: Timothy, Gross, USGS-BRD Florida Caribbean Science Center, 7920 NW 71st St., Gainesville, FL 32653, Phone: 352-378-8181 ext 323, Fax: 352-378-4956, Tim_s_gross@usgs.gov

(This abstract was taken from the Greater Everglades Ecosystem Restoration (GEER) Open File Report 03-54)

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