Comparative Assessment of Blood Mercury in American Alligators (Alligator mississippiensis) from Coastal North Carolina and Florida

Mercury (Hg) is a widespread and potential harmful persistent contaminate of aquatic ecosystems. Except for the northern most populations of American alligators ( Alligator Mississippiensis) found in North Carolina, the potential adverse health impacts of Hg on ecosystems and humans consuming alligator meat has been studied for over three decades. Now that alligators are being recreationally hunted and consumed across their range, it is especially important to monitor toxic contaminant levels to best understand possible adverse impacts of exposures on alligator populations and human health. In this study we evaluated blood Hg levels in American alligators from an urbanized site in Wilmington, NC, a nearby site at Lake Waccamaw, NC, and a site on the St Johns River in Florida. Median blood total Hg concentrations were particularly high at Lake Waccamaw (526 ng/g, range 152–946 ng/g), resulting in median muscle concentrations (0.48 ppm, range 0.13–0.88 ppm) above the US EPA/FDA fish consumption advisory level of 0.3 ppm. Median concentrations at the Wilmington site (69 ng/g, range 22–336 ng/g) were low, and Hg concentrations from the St Johns River site (143 ng/g, range 54–244 ng/g) were comparable to those reported in previous studies. Analysis of relationships between total Hg concentrations and a panel of blood chemistry biomarkers found only modest concentration dependent impact on biomarkers of renal function. The results of this study reveal that local environmental factors greatly impact Hg bioaccumulation in alligators, findings that reaffirm that local contaminant biomonitoring in alligator populations will be critical for affective management and determination of guidelines for safe consumption of harvested alligators.