Organochlorine Levels in Atlantic Seabirds

Abstract

SYNTHETIC organochlorine derivatives have been found in a variety of seabirds from the eastern North Pacific¹ and even the Antarctic², and considerable amounts of polychlorinated biphenyls (PCBs) in particular have been found in birds from the Baltic³, Dutch waters⁴ and the livers of starving common guillemots, Uria aalge, washed ashore around the Irish Sea in the autumn of 1969⁵. But comparatively few estimates of the amounts present in normal seabirds from the open North Atlantic have yet been published. We are reporting elsewhere⁶ the results of the investigation of over 100 birds from a representative range of species occurring between Scotland and the Arctic. In general they were all found to contain mainly PCBs and pp′-DDE, the former in greater concentration in every bird examined, in marked contrast to the North Pacific, where DDE levels are normally higher¹. The ratio of PCB to DDE was usually between two and ten in all species with the exception of the kittiwake, Rissa tridactyla, where the ratio was always higher. It is difficult to measure DDE in the presence of relatively high amounts of PCBs but in some of the kittiwakes this ratio was at least 60. This suggests that kittiwakes have a food source relatively high in PCBs compared with the other species or, less likely, that they metabolize or excrete DDE more rapidly than the other species.