Pollutant Levels, Antioxidants and Potential Genotoxic Effects in Incubating Female Common Eiders (Somateria mollissima)
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- Institutt for biologi 
In the present thesis, environmental exposure to 18 persistent organic pollutants (POPs) and 8 elements, as well as potential antioxidant responses and genotoxic effects in incubating female common eiders (Somateria mollissima) were investigated. Common eiders are long-lived, benthic feeding seaducks. Because only the females incubate the eggs, they fast for approximately 26 days during the incubation period. Consequently, female common eiders endure high natural nutritional stress, and when their fat reserves are mobilized during the nesting period, lipophilic POPs are redistributed from fat storage to the circulation. In this thesis, blood of female common eiders, nesting in Svalbard, was sampled at day 5 and at day 20 of incubation during two years. Whole blood was analysed for POP concentrations and DNA double-strand breaks (DNA DSBs) in the same individuals at both incubation times. During two years, blood concentrations of POPs were analysed at the end of the fasting incubation period in the Baltic Sea and in the Svalbard population of common eiders. Furthermore, element levels in blood and feather, as well as total antioxidant capacity (TAC), total glutathione (tGSH), carotenoids and DNA DSBs were analysed in both Baltic and Svalbard females after ~26 days of fasting. In the Baltic Sea, which has been considered one of the most polluted seas in the world, the population of common eiders is declining and considered endangered, while in Svalbard, the common eiders population is stable. To assess the impact of POP and element exposure on female common eiders during the fasting incubation, pollutant levels, antioxidant levels and DNA DSB frequencies were compared between these eider populations, potentially exposed to differing pollutant levels. The present thesis documented blood concentrations of most POPs, with the exception of four chlordane compounds and HCB, to be up to 26 times higher in the Baltic breeding common eiders compared to Svalbard eiders. Furthermore, blood concentrations of mercury (Hg) were higher in the blood of the Baltic females. The comparison of blood and feather concentrations of elements, however, indicated differing exposure levels for several elements at the breeding- and winter- location of the females. The frequency of DNA DSBs increased significantly during the fasting incubation period in Svalbard females. The decreased DNA integrity of Svalbard common eiders was positively related to body mass loss during the same period, but not to the increase in blood concentrations of POPs. Both TAC and tGSH concentrations were significantly up-regulated in the more polluted Baltic Sea population compared to the Svalbard population. The TAC was positively related to 14 POPs, but there was no relationship between any of the pollutants and tGSH concentrations. Furthermore, carotenoid levels did not differ between the two populations. Although the frequencies of DNA DSBs did not differ between the high-polluted Baltic Sea population and the less-polluted Svalbard population, Hg and POPs were positively related to DNA DSB frequencies in Baltic eiders, but not in Svalbard eiders. Hence, the present thesis documents an up-regulation in antioxidant defence and a potential genotoxic response to pollutant exposure in the higher-exposed Baltic Sea population of common eiders, while in the less-exposed Svalbard population pollutants did not appear to cause effects. The positive relationship between body mass loss and DNA DSB frequency in Svalbard eiders may, however, indicate that natural stressors are more important for reducing the DNA integrity than pollutant exposure in Svalbard eiders. The present thesis suggests that seabirds feeding at low trophic levels may accumulate relatively high concentrations of POPs in polluted areas, and that assessing the pollutant impact on these species may be of importance, in particular for those species of conservation concern.