Analysis of narwhal tusks reveals lifelong feeding ecology and mercury exposure

• Published in: Current Biology
• Main Authors: Dietz, Rune, Desforges, Jean-Pierre, Aubail, Aurore, Rigét, Frank, Garde, Eva, Ambus, Per, Drimmie, Robert, Heide-Jørgensen, Mads Peter, Sonne, Christian
• Other Authors: Department of Bioscience Aarhus, LIttoral ENvironnement et Sociétés (LIENSs), La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS), National Environmental Research Institute Danmark (NERI), Arctic Research Centre Aarhus (ARC), Aarhus University Aarhus, Greenland Institute of Natural Resources (GINR), Danmarks Tekniske Universitet = Technical University of Denmark (DTU)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2021
• Subjects: narwhal tusk; climate-induced dietary changes; temporal patterns; stable isotopes; d13C; d15N; mercury; food web; Arctic top predators; [SDV.TOX.TCA]Life Sciences [q-bio]/Toxicology/Toxicology and food chain; [SDE.BE]Environmental Sciences/Biodiversity and Ecology; Arctic; Greenland; Climate change; narwhal*; Sea ice
• Online Access: https://hal.science/hal-04295375; https://doi.org/10.1016/j.cub.2021.02.018

International audience The ability of animals to respond to changes in their environment is critical to their persistence. In theArctic, climate change and mercury exposure are two of the most important environmental threats fortop predators. Rapid warming is causing precipitous sea-ice loss, with consequences on the distribution,composition, and dietary ecology of species and, thus, exposure to food-borne mercury. Currentunderstanding of global change and pollution impacts on Arctic wildlife relies on single-time-point individualdata representing a snapshot in time. These data often lack comprehensive temporal resolution andoverlook the cumulative lifelong nature of stressors as well as individual variation. To overcome these challenges,we explore the unique capacity of narwhal tusks to characterize chronological lifetime biogeochemicalprofiles, allowing for investigations of climate-induced dietary changes and contaminant trends.Using temporal patterns of stable isotopes (d13C and d15N) and mercury concentrations in annually depositeddentine growth layer groups in 10 tusks from Northwest Greenland (1962–2010), we show surprisingplasticity in narwhal feeding ecology likely resulting from climate-induced changes in sea-ice cover, biologicalcommunities, and narwhal migration. Dietary changes consequently impacted mercury exposure primarilythrough trophic magnification effects. Mercury increased log-linearly over the study period, albeitwith an unexpected rise in recent years, likely caused by increased emissions and/or greater bioavailabilityin a warmer, ice-free Arctic. Our findings are consistent with an emerging pattern in the Arctic of reducedsea-ice leading to changes in the migration, habitat use, food web, and contaminant exposure in Arctic toppredators.