Abstract
Mercury (Hg) is an environmental contaminant which, at high concentrations, can negatively influence avian physiology and demography. Albatrosses (Diomedeidae) have higher Hg burdens than all other avian families. Here, we measure total Hg (THg) concentrations of body feathers from adult grey-headed albatrosses (Thalassarche chrysostoma) at South Georgia. Specifically, we (i) analyse temporal trends at South Georgia (1989–2013) and make comparisons with other breeding populations; (ii) identify factors driving variation in THg concentrations and (iii) examine relationships with breeding success. Mean ± s.d. feather THg concentrations were 13.0 ± 8.0 µg g−1 dw, which represents a threefold increase over the past 25 years at South Georgia and is the highest recorded in the Thalassarche genus. Foraging habitat, inferred from stable isotope ratios of carbon (δ13C), significantly influenced THg concentrations—feathers moulted in Antarctic waters had far lower THg concentrations than those moulted in subantarctic or subtropical waters. THg concentrations also increased with trophic level (δ15N), reflecting the biomagnification process. There was limited support for the influence of sex, age and previous breeding outcome on feather THg concentrations. However, in males, Hg exposure was correlated with breeding outcome—failed birds had significantly higher feather THg concentrations than successful birds. These results provide key insights into the drivers and consequences of Hg exposure in this globally important albatross population.
Highlights
Mercury (Hg) is a pervasive environmental contaminant that can negatively impact humans and wildlife [1]
The present study focuses on grey-headed albatrosses (Thalassarche chrysostoma) breeding at South Georgia—a remote island south of the Antarctic Polar Front (APF) in the Atlantic sector of the Southern Ocean
Grey-headed albatrosses are not in active body feather moult at Bird Island between October and February [43]; total Hg (THg) concentrations and stable isotope ratios of body feathers sampled during the breeding season should reflect Hg burdens, foraging areas and trophic levels when grown in the preceding nonbreeding period
Summary
Mercury (Hg) is a pervasive environmental contaminant that can negatively impact humans and wildlife [1]. Hg exposure tends to be high in this species, with intrapopulation variation reflecting its generalist feeding habits and wide foraging range [18] In this cross-sectional study, we measured feather THg concentrations in a very large sample of individuals of known age, sex and breeding history. Grey-headed albatrosses are not in active body feather moult at Bird Island between October and February [43]; THg concentrations and stable isotope ratios (see below) of body feathers sampled during the breeding season should reflect Hg burdens, foraging areas and trophic levels when grown in the preceding nonbreeding period.
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