PCBs are widely distributed and detectable far from anthropogenic sources. Northern elephant seals (Mirounga angustirostris) travel thousands of kilometers to forage in coastal and pelagic regions of the North Pacific. Our study (1) quantified PCB concentrations in adult female northern elephant seals at the start and end of their biannual foraging trips to assess if age, foraging region, or the fasting state and time of year had significant relationships with tissue concentrations, (2) examined PCB congeners relative to age, foraging region, and fasting state, and (3) examined correlations between tissue concentrations. Between 2005 and 2007 we sampled blubber (inner and outer layers) and serum before and after a foraging trip from 58 seals that carried satellite-tags and time-depth recorders. PCB concentrations in the inner blubber were significantly affected by the foraging trip and fasting state of the animal, with the highest concentrations observed at the end of the molting fast. Age did not significantly affect bulk PCB concentrations; however the proportion of PCB congeners with different degrees of chlorination was significantly affected by age, especially in the outer blubber. Younger animals had a significantly greater proportion of low-chlorinated PCBs (tri-, tetra- and penta-CBs) than older seals, with the opposite trend observed for hepta-CBs, indicating that an age-associated process significantly affects congener profiles. These results highlight the importance of sampling across the entire blubber layer when assessing toxicant levels in seals and taking into account both the fasting state and reproductive status of an animal when conducting contaminant research.
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