Meta-analytical and experimental studies investigating the effects of exposure to environmental contaminants in fish and amphibians

This thesis used meta-analytical and experimental studies to further the understanding of the effects of environmental contaminants (ECs) on fish and wildlife health and to provide data to support ecological risk assessment of priority substances. The first meta-analytic study (Chapter 2) summarizes the effect of EC exposure on fish glucocorticoid (GC) levels, and explores potential moderators that can account for variation in responses between studies. The findings from this study will improve the understanding of how ECs influence fish GC levels and will provide direction for future avenues of research. The first experimental study (Chapter 3) investigates the effects of two short-chain perfluoroalkyl carboxylic acids (PFCAs) on northern leopard frog (Rana [Lithobates] pipiens) tadpole growth and development metrics. The results suggest that short-chain PFCAs influence tadpole growth and development at environmentally-relevant concentrations. In addition, the short-chain PFCAs tested exhibited low bioconcentration potential in tadpoles. The next experimental study (Chapter 4) examines the chronic toxicity and bioconcentration of two short-chain perfluoroalkyl sulfonic acids (PFSAs) using northern leopard frog tadpoles. The results suggest that short-chain PFSAs influence tadpole hepatic health, alter tadpole lipid metabolism, and may exert endocrine-disrupting effects on tadpoles during early development. Similar to the previous experiment, PFSA concentrations in tadpoles were low, suggesting a low bioconcentration potential for short-chain PFSAs. These two experimental studies will provide essential information for ecological risk assessments of short-chain PFCAs and PFSAs. The second meta-analysis (Chapter 5) summarizes the relationship between EC exposure and amphibian susceptibility to parasitism. This study also explores potential moderators for the effects of EC exposure on amphibian susceptibility to parasitism. Additionally, this study identifies data gaps for several EC classes and parasite types. This chapter will further the understanding of factors contributing to increased amphibian susceptibility to parasitism after exposure to ECs, providing valuable information on factors potentially influencing amphibian population declines. Overall, this thesis highlights several important considerations for future ecotoxicity studies including establishing more rigorous reporting requirements for ecotoxicity studies, incorporating environmentally-relevant exposure concentrations, including multiple developmental stages of test subjects, and testing for net-effects of environmental contaminants.