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Marine Ecology Progress Series

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MEPS 195:261-268 (2000)  -  doi:10.3354/meps195261

Variability in mercury concentrations of great skuas Catharacta skua: the influence of colony, diet and trophic status inferred from stable isotope signatures

S. Bearhop1,*, R. A. Phillips2, D. R. Thompson3, S. Waldron4, R. W. Furness1

1Ornithology Group, Department of Environmental and Evolutionary Biology, Graham Kerr Building, University of Glasgow, Glasgow G12 8QQ, United Kingdom
2Department of Biological Sciences, University of Durham, South Road, Durham DH1 3LE, United Kingdom
3National Institute of Water & Atmospheric Research, 301 Evans Bay Parade, Greta Point, PO Box 14-901, Kilbirne, Wellington, New Zealand
4Scottish Universities Research and Reactor Centre (SURRC), East Kilbride, Glasgow G75 0QF, United Kingdom

ABSTRACT: A range of parameters thought to contribute to intra-specific variation in mercury levels were investigated using the feathers and blood of adult great skuas Catharacta skua from 2 northeast Atlantic colonies as sampling units. Different feather types and blood were taken to represent intake over different temporal scales. Mercury concentrations and stable isotope signatures of these tissues were determined. General linear models demonstrated that trophic status, as indicated by δ15N, had an influence on tissue mercury concentrations. However this effect was relatively minor compared to that of foraging area. Samples of the same feather types from the same individuals in consecutive years suggest that a factor other than dietary specialisation and foraging area is of major importance in determining intra-specific variability in mercury levels. It was concluded that there are a number of interacting factors contributing to intra-specific variability in mercury levels and the relative importance of these factors varies both spatially and temporally.

KEY WORDS: Mercury dynamics · Ttrophic status · Intra-specific variation · Carbon-13 · Nitrogen-15 · Stable isotopes

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