ECOLOGICAL EFFECTS OF ORGANOCHLORINE POLLUTANTS IN THE ARCTIC: A STUDY OF THE GLAUCOUS GULL

Since the early 1970s, high levels of long-transported organochlorine pollutants (OCs) such as PCBs and DDE have been found in seabirds in the European Arctic, especially in the Glaucous Gull, Larus hyperboreus. However, the potential ecological effects of these contaminants have not been studied. We measured the concentrations of 15 different OCs (HCB, three HCHs, oxychlordane, DDE, and nine PCB congeners) in the blood of 111 Glaucous Gulls and related the concentrations to fitness components of the same individuals. Blood samples were taken in 1997, and individuals were followed until 2000. We first conducted a principal component analysis (PCA) on all OCs and related reproductive traits and survival. to the first and second PCA axes, which represented persistent compounds and more volatile compounds, respectively. We then related reproductive traits and survival to all OCs separately, except for persistent PCB congeners (for which we used their sum), to test if some compounds were more consistently related to negative fitness effects than others. Females with high circulating levels of persistent OCs were more likely to lay nonviable eggs than were females with low levels, whereas levels of more volatile OCs were not related to egg viability. Moreover, there was a negative relationship between PC1, in addition to female blood concentration of both persistent and some volatile OCs, and the hatching condition of the chick from the first egg laid in clutches. The hatching condition of the second chick in clutches was significantly negatively related to PC1, and specifically to female blood concentrations of HCB, beta-HCH, and PCB-28. Apart from a negative association between OC concentrations and laying date in both sexes, no other reproductive parameters (clutch size, egg size, incubation time, nest predation, and early, chick survival) showed associations with any of the OCs measured. Hence, reproductive effects were most likely related to maternal transfer of persistent OCs to eggs. Adult survival was negatively related to blood concentration of DDE, persistent PCBs and HCB, and especially to oxychlordane. Survival probability was reduced by 29% in females and 16% in males as oxychlordane concentrations in the blood increased 10-fold (from 5 to 50 ng/k wet mass). In long-lived birds, adult survival probability is the parameter to which the population growth rate is most sensitive, suggesting that persistent OCs have the potential for causing considerable effects on the population dynamics of Arctic-breeding Glaucous Gulls.