The Role of DDE, PCB, Coplanar PCB and Eggshell Parameters for Reproduction in the White-tailed Sea Eagle (Haliaeetus albicilla) in Sweden.

• The reproduction of white-tailed sea eagles was monitoredin1964–1999 in 3 differently contaminated sub-populations: BalticSea coast (Bp), inland central Sweden (Ip) and Lapland (Lp). 249dead eggs from 205 clutches were obtained for analyses of DDEand PCBs and for eggshell measurements. A desiccation index(Di) value was calculated for each egg as a measure of waterloss through the shell. In the highly contaminated Bp, p,p´-DDEconcentrations in the eggs decreased continuously and 5-foldduring the study period and PCB concentrations decreased 3-fold from the mid 1980s. The PCB pattern changed slightly overtime towards more high-chlorinated congeners but the relativetoxicity of the PCB mixture, expressed as 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents (TEQ), remained constant and TEQcan be assumed to have decreased in a similar way as PCB overtime. Productivity (P), shell thickness (St), shell index (Si) and Diincreased over time in the Bp but no change in Di or productivityoccurred in the Lp, where residue concentrations were 5–8 timeslower. P of the Bp was not correlated to St or Si but was negatively correlated to Di, DDE and PCB. An S-shaped doseresponse relationship was indicated between P and DDE. After1988, when the PCB/DDE ratio was considerably higher thanpreviously, PCB but not DDE concentrations were significantlyhigher in eggs with dead embryos as compared to undevelopedeggs, implying lethal concentrations of PCB, and a LOEL of 320pg g–1 TEQ is suggested for embryo mortality. In a subset of 21eggs, representing productive and unproductive females, analyzed for a selection of coplanar PCB congeners, tris(4-chlorophenyl) methanol and bis(4-chlorophenyl) sulphone, there wasno evidence for a correlation between P and any of these compounds. A reduction in residue concentrations in old females didnot lead to increased P or improved Di-values, indicating aremaining effect from a previous, higher exposure to contaminants. The inability to reproduce included a high rate ofundeveloped eggs, indicating effects at a prezygotic stage. Pshowed the strongest correlation with Di, and Di was moststrongly correlated to DDE. Thus, the remaining effect of previousexposure resulted in a stronger correlation to the symptom (Di)rather than to the suggested causative agent (DDE). LOEL valuesfor depressed P were estimated at 120 µg g–1 DDE and 500 µgg–1 PCB (lipid basis). It is concluded that the major reason fordepressed P during the study period was DDE, but that effectsalso from PCB were largely concealed by the effects from DDE.

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