Mercury distribution in American alligators (Alligator mississippiensis) in Florida

Thirty American alligators (Alligator mississippiensis), including 24 wild-caught and six control captive farm-raised alligators, were analyzed for whole body mercury contamination. Wild-caught animals were collected from Water Conservation Area 3 in the Everglades ecosystem (n = 12) and from Alachua, Brevard, and Collier counties outside the Everglades (n = 12). Using cold-vapor atomic absorption spectrophotometry, samples of brain, cervical spinal cord, liver, paired kidneys, paired testes, paired ovaries, paired oviducts, heart, lungs, spleen, bile, tail and leg muscle, and tail and leg scales were analyzed on a wet weight basis to determine mercury concentration. Mercury was consistently detected in all specimens except for bile. Farm-raised alligators, fed a commercially prepared diet, contained very low mercury concentrations in all tissues analyzed. In comparison with alligators from outside the Everglades, Everglades alligators had significantly elevated concentrations of mercury in all tissues analyzed except ovaries, oviduct, bile, tail scales, and leg scales (paired two-sample Student's t-test, P < 0.05). Muscle concentrations exceeded state (0.50-1.50 ppm) and federal (1.00 ppm) allowances for safe human consumption in alligators collected in the Everglades. No clinical signs of neurologic, hepatic, or renal toxicosis were detected. Because of the alligator's ability to bioaccumulate mercury, this species might be useful as a biomonitor for environmental mercury contamination.