Tissue Mercury Concentrations in Alligators (Alligator mississippiensis) from the Florida Everglades and the Savannah River Site, South Carolina
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Mercury pollution is a serious problem in some areas of the southeastern United States. Due to biomagnification, long-lived predators should have high Hg concentrations in affected areas. American alligators (Alligator mississippiensis) are important predators in many southwestern wetlands, but little information is available on Hg concentrations in this species. We collected tissues from alligators inhabiting two sites in the Everglades, Florida (n = 18) and a manmade reservoir in South Carolina (Par Pond; n = 44), all with documented histories of Hg contamination, and analyzed them for total Hg. Mean concentrations in kidney, liver, muscle, and dermal scutes of alligators from the Everglades (expressed as mg Hg/kg dry mass ± S.E.M.) were 36.42 ± 5.23, 41.09 ± 5.90, 5.57 ± 0.47, and 5.83 ± 1.04, respectively. Concentrations in liver, muscle, and scutes from Par Pond alligators were 17.73 ± 2.56, 4.08 ± 0.46, and 4.58 ± 0.63, respectively. Blood from Par Pond alligators contained 2.20 ± 0.38 mg Hg/kg wet mass. Mercury concentrations did not differ among sexes at any location. Tissue Hg levels did not differ significantly between Everglades locations, but were lower in Par Pond. In Everglades alligators, Hg concentrations in all tissues were positively correlated, as were tissue Hg and total length. Only total length and scute Hg were correlated in Par Pond alligators. Regression revealed a significant relationship between muscle and scute Hg concentrations in Everglades alligators, but not Par Pond alligators. Alligators living in polluted areas can accumulate substantial concentrations of Hg, but relationships among Hg concentrations in specific tissues may vary with location or age and size of the animals sampled.
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