Bioaccumulation and biotransformation of persistent organochlorine contaminants in the arctic marine ecosystem

This study addressed the bioaccumulation and biotransformation of persistent organochlorine contaminants (OCs) in arctic marine biota with special emphasis on the bowhead whale (Balaena mysticetus), an endangered mysticete of sociocultural importance to the subsistence communities of northern Alaska. Limited information existed on the feeding ecology and OC concentrations in the bowhead whale and this study provided unique insight into the relationship between foraging behaviour and migration, and the subsequent effect on OC profiles accumulated in this species. Bioaccumulation and spatial distribution of OCs in prey of the bowhead whale and its associated food web were also investigated. The feeding ecology and OC accumulation in the arctic fox, a terrestrial/marine scavenger, was examined to provide an ecological context to the data. Differences in OC concentrations were related to several chemical- and species-specific factors, including biochemical (e.g. metabolic capability), behavioural (e.g. prey selection), and physicochemical (e.g. hydrophobicity, stereochemistry). In lower trophic biota such as zooplankton and fish, the bioaccumulation of OCs was primarily affected by the physical partitioning of contaminants, whereas biotransformation was more relevant in mammalian systems. Food web magnification factors were calculated for the marine food web of the southern Beaufort-Chukchi Seas region and statistically compared to other studies from the Arctic. Results demonstrate that spatial variability of OC contaminants in topmarine arctic predators is attributable to differences in regional sources of contaminant rather than trophic status. The accumulation of chiral OCs in arctic biota, including the enantiomerspecific biotransformation of chiral polychlorinated biphenyls (PCB atropisomers) in the bowhead whale, was examined. PCB biotransformation by the bowhead whale, as inferred from congener-specific accumulation profile relative to prey, suggests that cytochrome P450 (CYP) 2B-like isozyme activity was relatively low compared to other marine mammals and the arctic fox. However, the presence PCB metabolites, specifically methyl sulfone PCBs (MeSO₂-PCBs), in bowhead whale suggests that sufficient CYP2B-like isozyme activity exists for the biotransformation of some PCBs. However, the lack of significant concentrations of hydroxylated PCBs (OH-PCBs) implies that other factors may influence the accumulation of halogenated phenolic compounds in this cetacean.