Whole blood concentrations of organochlorines as a dose metric for studiesof the glaucous gull (Larus hyperboreus)

In order to examine if whole blood concentrations of organochlorines (OCs) is an appropriate dosimetric parameter for use in ecotoxicological studies of free-living birds, a number of incubating glaucous gulls (Larus hyperbor eus) were repeatedly sampled within and between subsequent breeding seasons . The wet weight concentrations of selected OCs, differing in persistence a nd fat solubility, were compared and it was assessed to what extent present concentrations could be predicted from concentrations previously measured in the individuals. There were only a few significant differences in the bl ood concentrations of the selected OCs within and between seasons. The most persistent compound, polychlorinated biphenyl (PCB)-153, showed a low inte rindividual variability, and between seasons, 70% of the variance could be explained by the level in the previous year, while changes in body conditio n and blood lipid percentage were of less importance. For PCB-101, the pred ictability of the present blood concentration from the previous concentrati on was lower than for PCB-153, and changes in body condition and blood lipi d percentage explained a higher proportion of the variance. The present lev el, of alpha -hexachlorocyclohexane (HCH) could not be predicted from the p revious level. Sex did not explain any significant proportion of the varian ce in OC concentrations when previous level and changes in body mass and bl ood lipid were included in the statistical models. Thus, for the most persi stent OCs, concentration in the blood of incubating glaucous gulls is repre sentative for the interindividual differences over time and whole blood con centrations of OCs appear adequate as a dose metric in ecotoxicological stu dies.