Multi-decadal trends in biomarkers in harp seal teeth from the North Atlantic reveal the influence of prey availability on seal trophic position.

Camille de la Vega, Joanna Kershaw, Garry B Stenson, Anne Kirstine Frie, Martin Biuw, Tore Haug, Louisa Norman, Claire Mahaffey, Sophie Smout, Rachel M Jeffreys

Global change biology 2023 Oct

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Arctic food webs are being impacted by borealisation and environmental change. To quantify the impact of these multiple forcings, it is crucial to accurately determine the temporal change in key ecosystem metrics, such as trophic position of top predators. Here, we measured stable nitrogen isotopes (δ15 N) in amino acids in harp seal teeth from across the North Atlantic spanning a period of 60 years to robustly assess multi-decadal trends in harp seal trophic position, accounting for changes in δ15 N at the base of the food web. We reveal long-term variations in trophic position of harp seals which are likely to reflect fluctuations in prey availability, specifically fish- or invertebrate-dominated diets. We show that the temporal trends in harp seal trophic position differ between the Northwest Atlantic, Greenland Sea and Barents Sea, suggesting divergent changes in each local ecosystem. Our results provide invaluable data for population dynamic and ecotoxicology studies. © 2023 The Authors. Global Change Biology published by John Wiley & Sons Ltd.

Citation

Camille de la Vega, Joanna Kershaw, Garry B Stenson, Anne Kirstine Frie, Martin Biuw, Tore Haug, Louisa Norman, Claire Mahaffey, Sophie Smout, Rachel M Jeffreys. Multi-decadal trends in biomarkers in harp seal teeth from the North Atlantic reveal the influence of prey availability on seal trophic position. Global change biology. 2023 Oct;29(19):5582-5595