PERSISTENT ORGANIC POLLUTANT LEVELS AND THE IMPORTANCE OF SOURCE PROXIMITY IN BALTIC AND SVALBARD BREEDING COMMON EIDERS

The distance to sources and the long-range transport potential of persistent organic pollutants (POPs) are important in understanding the impact of anthropogenic pollution on natural seabird populations. The present study documented blood concentrations of POPs in the Baltic Sea (Tvarminne, Finland) population of common eiders (Somateria mollissima) in 2009 and in 2011 and compared the concentrations with the presumably less exposed Arctic population in Svalbard (Kongsfjorden, Norway). The Baltic population had 26, 10, and 5 times greater concentrations of hexachlorocyclohexane, polychlorinated biphenyls, and p,p'-dichlorodiphenyldichloroethylene than the Svalbard population. Unexpectedly, concentrations of chlordanes were higher in Svalbard eiders, whereas concentrations of hexachlorobenzenes (HCBs) did not differ between the 2 populations. Although the similar HCB levels may partly be explained by the high transport potential of HCBs, unknown factors may have been more important than distance to sources and long-range transport potential for the chlordanes. One plausible explanation may be that the fasting-related redistribution of POPs from fat to blood was greater throughout the incubation in Arctic eiders, causing them to have higher blood levels of these POPs at the end of incubation. The blood concentrations of POPs in Baltic eiders were higher than documented in any other eider population and were comparable to levels in seabirds feeding at higher trophic positions in the food chain.