Seasonal fluctuations of organochlorine levels in the common eider (Somateria mollissima) in Iceland

Breast muscle of 55 common eiders (Somateria mollissima) and liver samples of 12 birds, caught at Skerjafjör[z.eth]ur in SW-Iceland in February, May, June and November 1993 were analysed for organochlorine contamination (10–30 different congeners of PCBs, pp′-DDT, -DDE, -DDD, HCB, α-, β-, and γ-HCH). The levels of the contaminants were similar in both tissues and were at their lowest in February. A substantial increase (up to 10-fold) in the levels of all substances was observed in June, in the females, which at that point had lost about one-third of their late winter body weight. The increase may be due to relocation to other tissues of organochlorines stored in the shrinking bodyfat. During this period the birds must be vulnerable to the toxic effects of these chemicals as they can transiently reach high concentrations in the blood. The levels found were similar or higher than those recently reported for eiders from Spitsbergen, the NWT of Canada and Frans Josefs Land of Russia, especially the levels of PCBs.