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An Evaluation of Contaminant Exposures and Potential Effects on Health and
Endocrine Status for Alligators in the Greater Everglades Ecosystem.
Jon, J. Wiebe, Ken Rice, Carla M. Wieser, and Timothy S. Gross
USGS-BRD Florida Caribbean Science Center and the University of Florida,
Gainesville, FL.
Alterations in sexual differentiation, endocrine function and health has been
documented among alligators 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 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 for 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, Loxahatchie 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 detectable 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)
Blood
400
Muscle
350
S cute
300
Liver
250
200
150
100
50
0
Loxahatchie
Big Cypress
WCA-2A
WCA-3AN
WCA-3AS
ENP
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
350
DDE
Methoxychlor
300
Chlordane
250
Dieldrin
Toxaphene
200
150
Atrazine
Diazinon
100
50
0
Loxahatchie
B ig Cypress
WCA-2A
WCA-3AN
WCA-3AS
ENP
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.
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.
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
[email protected],