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An Evaluation of Contaminant Exposures and Potential Effects on Health and Endocrine Status for Alligators in the Greater Everglades Ecosystem

By Jon J. Wiebe, Ken Rice, Carla M. Wieser, and Timothy S. Gross
USGS, Center for Aquatic Studies and the University of Florida, Gainesville, FL., USA

Alterations in sexual differentiation, endocrine function and health have been documented among alligators in Central Florida as a potential response to environmental contaminants. These data suggest that exposure to sitespecific sources, primarily agricultural sites and pesticides, may be responsible for these toxicities. The assessment of exposures for alligators 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 on alligators in the Greater Everglades Ecosystem. Alligators (approximately 5 ft in length; n=10 animals per site during Fall 1999 and 2000) were collected and sacrificed from several specific sites involved in future restoration efforts: Everglades National Park, Loxahatchee National Wildlife Refuge, Big Cypress National Preserve, and Water Conservation Areas 2A, 3A-N and 3A-S. Several tissues were collected for contaminant analysis: blood, scute, liver, muscle, bile, and fat. 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. Selected samples from several alligators were composited to assess the appropriate tissues for each contaminant analysis. Samples collected during 1999 (approx. 3 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 for 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 and scute. Blood and scute 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. Muscle tissue (i.e. fillets) were 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 three alligators from each site and preliminary results are summarized in figures 1 and 2.

bar graph of total organochlorine hydrocarbon pesticides for several tissue types from alligators across several Everglades regions
Figure 1. Preliminary analysis of total organochlorine hydrocarbon pesticides for several tissues from alligators 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 for each tissue. Note the differential distribution of pesticides across tissues. [larger image]

bar graph of various organochlorine pesticides in the muscle tissue of alligators across several regions within the Everglades
Figure 2. Preliminary analysis of organochlorine pesticides in muscle tissue for alligators across several regions within the Greater Everglades ecosystem. Data is listed as ppb. Note the increased exposures at the WCA’s as compared to the other sites. [larger image]

Results indicate site-specific patterns of contaminant exposure for alligators 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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