Assessing Bivalves as Biomonitors of Per- and Polyfluoroalkyl Substances in Coastal Environments.

Per- and polyfluoroalkyl substances (PFAS) are widely used chemicals that enter coastal ecosystems through various pathways. Despite the ecological and economic significance of coastal environments, monitoring efforts to identify PFAS in these regions are limited. Bivalves have been used as biomonitors for many pollutants, but their effectiveness in reflecting environmental PFAS contamination and the mechanisms of PFAS bioaccumulation is poorly understood. This study examined the impact of biological, chemical, and ecological variables on PFAS bioaccumulation in two bivalve species (i.e., Eastern oyster and Atlantic ribbed mussel) and developed a statistical model to predict the PFAS content in wild bivalves. Overall, the summed PFAS concentration in the bivalves closely mirrors that in water. We observed higher bioaccumulation factors for some perfluoroalkyl sulfonamides and branched PFAS isomers than for terminal PFAS of equivalent chain length. The isomer distribution and precursor-to-terminal compound ratios provide compelling evidence that the biotransformation of PFAS precursors likely drives these elevated factors. Additionally, the bioaccumulation factors of PFAS decrease with increasing organism size and age, suggesting that smaller and younger bivalves have greater bioaccumulation potential and are more susceptible to PFAS contamination. These findings provide critical information that guides the use of bivalves as biomonitors to evaluate PFAS contamination in aquatic environments.