Evaluating mercury concentrations and body condition in American alligators (Alligator mississippiensis) at Merritt Island National Wildlife Refuge (MINWR), Florida

• Published in: The Science of the total environment 2017-12, Vol.607-608, p.1056-1064
• Main Authors: Nilsen, Frances M., Dorsey, Jonathan E., Lowers, Russell H., Guillette, Louis J., Long, Stephen E., Bowden, John A., Schock, Tracey B.
• Format: Article
• Language: English
• Subjects: Alligator; Alligators and Crocodiles - blood; Animals; Behavior; Environmental Exposure - analysis; Environmental Pollutants - blood; Female; Florida; Health; Male; Mercury; Mercury - blood; Seasonal
• ISSN: 0048-9697; 1879-1026; 1879-1026
• DOI: 10.1016/j.scitotenv.2017.07.073

Concentrations of mercury (Hg) are not well studied in free-ranging wildlife. Atmospheric deposition patterns of Hg have been studied in detail and have been modeled for both global and specific locations and often correlate to environmental impact. However, monitoring the impact of Hg deposition in wildlife is complicated due to local environmental conditions that can affect the transformation of atmospheric Hg to the biologically available forms (e.g., rainfall, humidity, pH, the ability of the environment to methylate Hg), as well as affect the accessibility to organisms for sampling. In this study, Hg concentrations in blood samples from a population of American alligators (Alligator mississippiensis) at Merritt Island National Wildlife Refuge (MINWR), FL, USA, over a seven-year period (2007 to 2014; n=174 individuals) were examined to assess Hg variation in the population, as well as the difference in Hg concentration as a function of health status. While most of this population is healthy, 18 individuals with low body mass indices (BMI, defined in this study) were captured throughout the sampling period. These alligators exhibited significantly elevated Hg concentrations compared to their age/sex/season matched counterparts with normal BMI, suggesting that health status should be taken into account when examining Hg concentrations and effects. Alligator blood Hg concentrations were related to the interaction of age/size, sex, and season. This study illustrates the value of a routinely monitored population of large predators in a unique coastal wetland ecosystem, and illuminates the value of long-term environmental exposure assessment. An American alligator residing in Merritt Island National Wildlife Refuge, FL. Photo taken in front of NASA's Kennedy Space Center Vehicle Assembly Building by Louis J. Guillette Jr. [Display omitted] •Mercury concentrations in blood of alligators were investigated (2007–2014).•Index created for monitoring the health status of alligators using body condition.•Alligators with low BMI coincided with elevated mercury concentrations.•Size is a significant predictor of mercury concentration in female alligators.