LAUSR

This study examines how southern wintering areas may contribute to organochlorine (OCs) loads in arctic seabirds during breeding. Light-sensitive geolocators (GLS loggers) were deployed on Arctic skuas (Stercorarius parasiticus) in one high arctic and two subarctic colonies. Hexcahlorobenzene (HCB), Chlordanes, Mirex, p, p'-dichlorodiphenyldichloro- ethylene (p, p'-DDE), and Polychlorinated biphenyls (PCBs) were measured in the blood of breeding adults at the nest (58 individuals, a total of 128 samples) in northern Norway and Svalbard between 2009 and 2015. We compared OC concentrations and OC profiles among nesting skuas wintering in five Atlantic regions, determined by the GLS loggers: the coast of Argentina, the Caribbean, the coast of western Africa, the coast of Southern Africa, and the Mediterranean Sea. As predicted, HCB, which is semi-volatile and has high long-range transport potential, showed high prevalence in birds wintering in all regions except the Mediterranean. Mirex showed the highest prevalence in birds wintering off the coasts of Argentina and southern Africa, in accordance with high background levels previously documented in the Southern Ocean. Chlordanes were particularly prevalent in skuas wintering off southern Africa, whereas p, p'-DDE seemed relatively evenly distributed among wintering areas. As predicted, the prevalence of PCBs was much higher in birds wintering in the Mediterranean Sea than in birds from other regions. This study thus suggests that the Mediterranean Sea, the mid- and southern Atlantic are essential sources of different OCs in the blood of Arctic skuas breeding in the European Arctic.