Accumulation and lactational transfer of PCBs and pesticides in harbor seals ( Phoca vitulina) from Svalbard, Norway

Abstract

The harbor seal population on Svalbard, the northernmost breeding site for this species, appears to have a truncated age distribution with older animals being largely absent. PCBs and pesticides were measured in harbor seal males, females, milk and pups from Svalbard to explore whether contaminant exposure or accumulation is a possible cause of premature death for these animals. The levels and patterns of these contaminants were assessed. In addition, transfer of these compounds from females to their pups during lactation was assessed. Both PCB and pesticide levels were low compared to more southern harbor seal populations. Animals from Svalbard contained 5–10 times lower contaminant levels, compared to seals from the Norwegian mainland, and 30 times lower concentrations than those of harbor seals from the Gulf of St. Lawrence in eastern Canada. Ringed seals from Svalbard have contaminant levels that are comparable to the harbor seals, probably because the diet, as well as the metabolic capacity, of the two species is similar at this location. The findings of this study indicate that the early mortality observed for harbor seals on Svalbard, is not likely to be due to contaminant exposure. Female harbor seals transfer a modified contaminant mixture to their pups compared to that found within their own tissues; compounds with higher log K ow, such as some penta-chlorinated PCBs, were selectively transferred into milk. As a result, the contaminant pattern between males and females differed, with penta-chlorinated PCBs more abundant in males than in females. In addition, pups receive a relatively high amount of the less lipophylic compounds and a low amount of the more lipophylic compounds. The similar contaminant pattern in milk and pups suggested that they are probably unable to metabolize contaminants and consequently, accumulate all ingested chemicals.