Temporal trends of selected POPs and the potential influence of climate variability in a Greenland ringed seal population

Temporal trends of selected POPs (PCB-52 and 153, p, p'-DDE, HCB, alpha-and beta-HCH) in blubber of ringed seals (Pusa hispida) collected from the early 1990s to 2010 from central West Greenland were studied. In this period, the climate of Greenland warmed and the influences of climate indices such as winter sea-ice coverage (November-May), the number of sea-ice days during winter in Disko Bay, water temperature and salinity at Fyllas Banke during the preceding summer and the Arctic Oscillation Index (AOI) during the preceding winter on concentrations of selected POPs were evaluated using multiple regressions and an information-theoretic approach. Biological co-variables such as age, sex and trophic position (as determined by delta N-15 analysis) of seals were also evaluated. Decreasing levels of the selected POPs were found in all cases and with the highest rate for alpha-HCH (-10.5% annually) and the lowest rate for beta-HCH (-1.9% annually). Sex and age were found to have strong predictive power in the case of PCB-52 and trophic position in the case of p,p'-DDE. Among the climate indices the strongest predictive power was found for the number of sea-ice days in the case of PCB-52, the AOI winter index in the case of alpha-HCH and salinity at Fyllas Banke during the preceding summer in the case of beta-HCH. The present study documents the need for including both biological variables and climate variability parameters in temporal trend studies of POPs in Arctic biota.