John Wiley & Sons, Ltd.

Metabolic transformation shapes PCB and PBDE patterns in beluga whales (Delphinapterus leucas)

While the accumulation of persistent contaminants in marine mammals can be attributed directly to their prey, the role of metabolism in shaping patterns is often overlooked. Here we investigate the role of metabolic transformation in influencing polychlorinated‐biphenyl (PCB) and polybrominated diphenylether (PBDE) patterns in offshore and nearshore groups of beluga whales (Delphinapterus leucas) and their prey. Congener profiles and principal components analysis (PCA) revealed similar PCB and PBDE patterns in beluga whales feeding either offshore or nearshore, despite divergent contaminant patterns in the putative prey of these two feeding groups. The clustering of PCBs into metabolically‐derived structure‐activity groups (SAG), and the separation of metabolizable and recalcitrant groups along PC1 of the PCA, revealed the important role of metabolic transformation in shaping PCB patterns in beluga. Lack of metabolism for congeners with high ortho‐chlorine content was revealed by metabolic slopes equal to or greater than 1.0. Metabolic slopes for all other structure‐activity groups were <1.0 (p<0.001), indicating metabolism of congeners with ortho‐meta and meta‐para vicinal hydrogens via induction of cytochrome‐P450 enzymes (CYP1A/2B/3A). Metabolic indices <1.0 for PBDEs (p<0.001) suggested that beluga are metabolizing these poorly understood flame retardants. The strikingly similar PCB patterns in a captive beluga and free‐ranging beluga from the Beaufort Sea provide additional evidence that metabolic transformation is a dominant driver of contaminant patterns in beluga. Environ. Toxicol. Chem. © 2013 SETAC

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