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Abstract
Mercury (Hg) is a global pollutant of concern capable of contaminating aquatic and terrestrial environments. Unlike many other metals, Hg is well-known due to its propensity to bioaccumulate, biomagnify, and maternally transfer in vertebrates. The detrimental effects of Hg exposure in vertebrates include neurotoxicity, impaired growth, decreased reproductive success, and reduced survival. Although these effects have been described in mammals and birds, little is known about the bioaccumulation and effects of Hg in reptiles, especially snakes. All snakes are predators, typically occupy upper-level trophic positions in their respective food webs, and many are long-lived. These characteristics suggest snakes may be effective biomonitors for Hg contamination. In this dissertation, I explored how a common watersnake species, the brown watersnake (Nerodia taxispilota), may be used to evaluate spatial and temporal trends in Hg contamination in a major riverine system in the southeastern United States. Next, I optimized an in vitro immune-based assay in N. taxispilota, providing a framework for the investigation of how mitogens, contaminants, and other stressors may impact their immune response. With Hg data from previous studies, I then examined how in vitro exposure to Hg affected lymphocyte proliferation in N. taxispilota. Overall, my results demonstrate that N. taxispilota can be effective biomonitors for Hg contamination in a riverine system, providing risk assessors with novel data that will aid in future investigations of snake ecotoxicology. In addition, my results suggest that N. taxispilota from the Savannah River (adjacent to the Savannah River Site) are at low risk of Hg immunotoxicity. However, Nerodia spp. in heavily contaminated systems in other areas of the United States could be subject to negative impacts due to Hg exposure.