1046 Environmental Toxicology and Chemistry, Vol. 20, No. 5, pp. 1046–1052, 2001  2001 SETAC Printed in the USA 0730-7268/01 $9.00 + .00 WHOLE BLOOD CONCENTRATIONS OF ORGANOCHLORINES AS A DOSE METRIC FOR STUDIES OF THE GLAUCOUS GULL (LARUS HYPERBOREUS) JAN O. BUSTNES,*² J ANNECHE U. SKAARE,‡ KJELL E. ERIKSTAD,² V IDAR BAKKEN,§ and FRITJOF MEHLUM§ ²Norwegian Institute for Nature Research, Division of Arctic Ecology, The Polar Environmental Centre, N-9296 Tromsø, Norway ‡National Veterinary Institute, PO Box 8156 Department, N-0033 Oslo, Norway §Norwegian Polar Institute, University of Oslo, Zoological Museum, Sarsgate 1, N-0562 Oslo, Norway ( Received 29 February 2000; Accepted 20 September 2000) Abstract—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 hyperboreus) were repeatedly sampled within and between subsequent breeding seasons. The wet weight concentrations of selected OCs, differing in persistence and 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 blood concentrations of the selected OCs within and between seasons. The most persistent compound, polychlorinated biphenyl (PCB)-153, showed a low interindividual variability, and between seasons, 70% of the variance could be explained by the level in the previous year, while changes in body condition and blood lipid percentage were of less importance. For PCB-101, the predictability of the present blood concentration from the previous concentration was lower than for PCB-153, and changes in body condition and blood lipid percentage explained a higher proportion of the variance. The present level of -hexachlorocyclohexane (HCH) could not be predicted from the previous level. Sex did not explain any significant proportion of the variance in OC concentrations when previous level and changes in body mass and blood lipid were included in the statistical models. Thus, for the most persistent OCs, concentration in the blood of incubating glaucous gulls is representative for the interindividual differences over time and whole blood concentrations of OCs appear adequate as a dose metric in ecotoxicological studies. Keywords—Organochlorines Blood sampling Incubation Arctic Glaucous gull INTRODUCTION A problem in ecotoxicology has been to measure concen- trations of environmental contaminants in wildlife populations nondestructively. This is critical in long-term population stud- ies where relationships between contaminants and population parameters (i.e., reproduction and survival) are investigated since such studies often depend on monitoring individuals for extended periods of time. Thus, methods enabling researchers to achieve an appropriate dose metric for contamination loads of individuals and subsequently record their fitness have great advantages [1–3]. Organochlorines are lipophilic and persistent substances that are usually measured in tissues such as liver, brain, muscle, or subcutaneous fat. This is mainly because such tissues are target tissues for toxic effects of the contaminants and contain the bulk of the individual body burden [4,5]. However, in ecotoxicological studies, use of body fluids would be advan- tageous because it is nondestructive, and recently, various methods have been developed to measure organochlorine (OC) levels in plasma and whole blood [1,6–10]. Henriksen et al. [2] showed that, in captive glaucous gulls (Larus hyperbo- reus), there was a close relationship between OC concentra- tions in blood and tissue lipids and a strong correlation in OC concentrations between blood sampled from the same indi- viduals three to five weeks apart. No corresponding studies have been made in free-living gulls but are desirable because extrapolation of experimental data from captive birds may be unreliable. Varying environmental conditions can cause with- * To whom correspondence may be addressed (jan.o.bustnes@ninatos.ninaniku.no). in- and between-season changes in metabolic rate and fat stor- age, which are basic determinants of toxicokinetic behavior of persistent and bioaccumulative contaminants [11]. To relate OC burdens to possible ecological effects, it is crucial to know whether individuals have chronically higher burdens over time or if the concentration in the measuring compartment is heavily influenced by intraindividual temporal variability. Hence, is there a high interindividual correlation between measurements taken at different times or do other individual factors, such as body condition, sex, or exposure, confound interpretation of concentrations? In order to examine if OC concentration in whole blood is an appropriate dose metric in ecotoxicological studies of incubating glaucous gulls, we repeatedly sampled the same individuals and tested how much of the short-term (within a breeding season) and long- term (between breeding seasons) variability in OC levels could be predicted from previous concentrations compared with oth- er factors known to influence the toxicokinetic behavior of the OCs. We used wet weight concentrations because they are considered most relevant in studies of effects of OCs [5,12,13]. MATERIALS AND METHODS The study was carried out at Bear Island (northeastern At- lantic, 74°30'N, 19°01'E) in 1997 and 1998. Details about the study area have been described in Bustnes et al. [14]. Adult glaucous gulls were caught at their nests using a nest trap, consisting of a snare placed on the edge of the nest bowl attached to an elastic rope. The trap was triggered by a radio transmitter. The birds were equipped with letter-coded poly- vinyl chloride leg bands and numbered steel bands. Several measurements were recorded for each individual (wing, bill,