Increasing salinity exacerbates the bioaccumulation and toxicity of perfluorooctanoic acid (PFOA) in Manila clams...

Perfluorooctanoic acid (PFOA) is a widespread pollutant of emerging concern in marine environments. Salinity, a key regulator of pollutant dynamics behavior in estuarine and coastal areas, remains an understudied factor influencing PFOA bioaccumulation and toxicity in marine organisms. This study investigated the bioaccumulation, distribution, elimination, and toxic effects of PFOA in Manila clams (Ruditapes philippinarum) exposed to 200 μg/L PFOA for 21 days under three salinity conditions (20, 28, and 36 psu). Increased salinity significantly enhanced the PFOA bioconcentration factor and accumulation in Manila clams, with the hepatopancreas identified as the primary target organ. This enhancement was attributed to salinity-driven increases in hemolymph osmolality, filtration rates, and PFOA binding to proteins. Biomarker responses and the integrated biomarker response (IBR) index revealed that PFOA induced oxidative stress and disrupted energy and ion homeostasis, with higher response levels observed under elevated salinity. Histopathological examination further confirmed interactive tissue damage in the hepatopancreas from combined high-salinity and PFOA exposure. Thus, this study demonstrated that salinity fluctuations critically modulated both the bioaccumulation and toxicity of PFOA in Manila clams, underscoring the need to incorporate salinity as a key environmental variable in ecological risk assessments for PFOA in estuarine and coastal regions.