Pfas bioaccumulation, depuration, and associated energetic costs in the Eastern oyster Crassostrea virginica

Per-, and polyfluoroalkyl substances (PFAS) are a class of man-made chemicals that are widespread and persistent in the environment. Impacts of PFAS on the health of oysters are an emerging concern to conservationists and oyster farmers alike. Depuration of contaminants has been shown to be energetically expensive in some bivalves and there is concern that this metabolic cost may have a negative effect on organismal health. To address bioaccumulation concerns, eastern oysters (Crassostrea virginica) were exposed to a mixture of PFAS (PFOS, PFOA, PFHxA, PFPeA, PFBS) at a nominal concentration of 2 µg/L per compound for 28-days and then transferred to clean water for 5-days. Concentration of PFAS in soft tissues was measured on a subset of oysters seven times throughout exposure using an ultra-high performance liquid chromatography coupled to triple quadruple mass spectrometry (UHPLC-QqQ-MS) to determine PFAS bioaccumulation and subsequent depuration. Bioaccumulation factor was higher for >6 carbon chained compounds compared to <6 carbon chained compounds and PFAS tissue concentration was below detection limits within 24-hr of transfer to clean water. To determine metabolic cost of PFAS exposure and depuration, an additional group of oysters were exposed to either a mixture of PFOS + PFOA (5 µg/L each) or a mixture of PFOS, PFOA, PFHxA, PFPeA, PFBS (2 µg/L each) for 10-days and optical respirometry was used to assess changes in mass-specific oxygen uptake (MO2). There was no significant difference in MO2 between treatment and control oysters during exposure or during depuration. There was no evidence that exposure and depuration of PFAS mixtures at concentrations higher than measured in coastal environments adversely impacted oyster metabolism.