THE UPTAKE AND EFFECTS OF POLY- AND PERFLUOROALKYL SUBSTANCES ON LARVAL AND JUVENILE AMPHIBIANS
thesisposted on 17.01.2019, 14:40 by Sarah A. Vaughn
Poly- and perfluoroalkyl substances (PFAS) are ubiquitous contaminants across the globe, can bioaccumulate in aquatic taxa, and potentially biomagnify in food webs. Consequently, research examining the influence of PFAS on wildlife is warranted. Amphibians are sensitive to contaminants such as PFAS because of their porous skin and associations with aquatic habitats where contaminants accumulate. Because PFAS tend to bioaccumulate and can adversely affect the endocrine system, there is a need to examine uptake rates to inform ecotoxicology studies, as well as a need to examine sublethal effects. To address these knowledge gaps I conducted two experiments. First, I exposed larval northern leopard frogs (Rana pipiens), American toads (Anaxyrus americanus), and eastern tiger salamanders (Ambystoma tigrinum) to PFAS chemicals perfluorooctanoic acid (PFOA) or perfluorooctane sulfonate (PFOS) at concentrations of 10 or 1000 ppb for 10 days and sampled them every 48 hours during the exposure period. In the next experiment, I examined the effects of PFAS exposure via contaminated substrate on the survival and growth of post metamorphic amphibians of the same species. I found that, for all species, body burdens often reached steady state within 48 to 96 h of exposure. Steady-state body burdens of PFOA ranged from 3,819–16,481 ng/g dry weight among treatments and species (corresponding BCFs of 0.5 to 2.5), while PFOS body burdens ranged from 6,955–489,958 ng/g dry weight (corresponding BCFs of 47–259) among treatments and species. These data suggest that steady state is rapidly reached in larval amphibians exposed to PFAS, particularly regarding PFOS. This reflects a high potential for trophic transfer of PFAS within food webs because amphibians are often low in trophic position and are important prey for many aquatic and terrestrial species. In post-metamorphic amphibians, there was no influence of PFAS on survival or mass. However, significant effects on snout-vent length were observed in all species, and body condition differences were observed for two of my species. I found that all leopard frogs increased in scaled mass index (SMI) when exposed to a PFAS treatment, indicating an increased body condition. Toads exhibited a more variable SMI pattern across treatments, with no outstanding trends, and tiger salamanders did not differ significantly across treatments. These data suggest that sublethal effects vary greatly depending on the species, possibly due to life history traits. Future research examining biomagnification potential is warranted to determine the influence of PFAS on food webs. Additionally, there is a need to determine the physiological mechanisms underlying the observed effects of PFAS exposure.