Effects of Environmentally Relevant PFOS Concentrations on Unionid Bioaccumulation, Benthic-pelagic Coupling, and Gene Expression

Abstract

Per- and polyfluoroalkyl substances (PFAS) are persistent organic chemicals that have high energy carbon and fluorine bonds that make them resistant to metabolic breakdown and degradation. These substances are emerging containments of interest that are very widespread in the environment today. Perfluorooctanesulfonic acid (PFOS) is a type of PFAS that was created in the 1950s and can be found in fire prevention agents, weatherproof clothing, and other everyday household items. Alabama waterways host the highest diversity of unionid mussels (Unionidae) in the world but the majority of the species in the state are threatened and/or declining. PFOS has been detected in many of Alabama waterways and poses a potential threat to unionids. In the present study, we examined the effects of feeding on unionid bioaccumulation of PFOS, the effects of unionid size on tissue and sediment PFOS concentration, whether the presence of unionids resulted in the enrichment of PFOS in surrounding sediments, and if environmentally relevant concentrations of PFOS caused a gene expression change in the gills and mantle tissue of male and gravid female unionids. We found that bioconcentration of PFOS by fasted unionids was greater than bioaccumulation by fed unionids, but no evidence that PFOS body burden was affected by size of adult unionids. Sediment PFOS concentrations increased significantly in the presence of unionids suggesting that bivalves may affect non-trophic pathways of PFOS bioaccumulation in benthic invertebrates via benthic-pelagic coupling. We found no significant response in Bag 4, HSP 70 or Krüppel 5 gene expression in either the male and female gills or in female mantle tissue. However, there was a 2.37-fold change in the Krüppel 5 gene expression in the male mantle tissue suggesting that environmentally relevant PFOS concentration may influence pathways regulated by the Krüppel 5 gene.