Influence of species‐specific feeding ecology on mercury concentrations in seabirds breeding on the Chatham Islands, New Zealand
Résumé
Mercury (Hg) is a toxic metal which accumulates in organisms and biomagnifies along food webs, and hence, long-lived predators such as seabirds, are at risk due to high Hg bioaccumulation. Seabirds have been widely used to monitor the contamination of marine ecosystems. Here, we investigated Hg concentrations in blood, muscle and feathers of seven Procellariform seabirds breeding on the Chatham Islands, New Zealand. Using bulk and compound-specific stable isotope ratios of carbon and nitrogen as a proxy of trophic position and distribution, we also tested whether Hg contamination is related to the species-specific feeding ecology. Hg exposure varied widely within the seabird community: the highest contaminated species, the Magenta petrel, had ~29 times more Hg in blood than the broad-billed prion and ~35 times more Hg in feathers than the grey-backed storm petrel. Variation of Hg concentrations in blood and feathers were significantly and positively linked to feeding habitats and trophic position, highlighting the occurrence of efficient Hg biomagnification processes along the food web. Species and feeding habitats were the two main drivers of Hg exposure within the seabird community. Pterodroma species had high blood and feather Hg concentrations, which can be due to their specific physiology and/or due to their foraging behaviour during the interbreeding period (i.e., from the Tasman Sea to the Humboldt Current system). These two threatened species are at risk of suffering detrimental effects from Hg exposure and further studies are required to investigate potential negative impacts, especially on their reproduction capability.
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