Active biomonitoring of PFAS in Asian Clams: Associations with oxidative stress, respiration and condition index

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental pollutants that accumulate in aquatic ecosystems, posing a threat to wildlife. This study examines the potential of Asian clams (Corbicula fluminea) as an active biomonitoring species for assessing PFAS contamination in the Scheldt River, Belgium. Clams were exposed in cages at six sites along the river for a six-week exposure period, with simultaneous collection of sediment and water samples at each site. To evaluate the effects of PFAS bioaccumulation under natural conditions, three endpoints, oxidative stress, condition index, and respiration rate, were measured and analyzed in relation to bioaccumulated PFAS concentrations. The results revealed significant bioaccumulation of both legacy and emerging PFAS in clams, exhibiting distinct spatial patterns across sampling sites. In water samples, short-chain PFAS were predominant, whereas long-chain PFAS were primarily detected in sediments. Notably, only one compound, PFOA, was detected across all three matrices. Furthermore, Asian clams bioaccumulated three PFAS compounds, PFDA, PFTeDA, and NaDONA, that were not detected in water or sediment samples, underscoring the critical role of biomonitoring in detecting contaminants that may be overlooked in abiotic assessments. Biomarker analysis suggested oxidative stress responses to PFAS exposure, with significant positive correlations between malondialdehyde (MDA) levels and PFAS concentrations (NaDONA, PFDoDA, PFTeDA and ∑PFAS), suggesting lipid peroxidation as a potential mechanism of PFAS-induced cellular damage. Additionally, the condition index of the clams showed significant negative correlations with PFAS concentrations (NaDONA, PFOA and ∑PFAS), indicating potential physiological impairment. However, no significant relationships with respiration rates were observed. These findings demonstrate the utility of Asian clams as effective biomonitors for PFAS contamination and suggest of physiological and molecular responses to PFAS exposure in aquatic environments.