TY - JOUR

T1 - Analysis of narwhal tusks reveals lifelong feeding ecology and mercury exposure

AU - Dietz, Rune

AU - Desforges, Jean-Pierre

AU - Rigét, Frank F.

AU - Aubail, Aurore

AU - Garde, Eva

AU - Ambus, Per

AU - Drimmie, Robert

AU - Heide-Jørgensen, Mads Peter

AU - Sonne, Christian

N1 - Funding Information: Local hunters from Avanersuaq and Uummannaq are acknowledged for providing the narwhal tusks taken during their aboriginal hunt. Jeppe M?hl was responsible for cutting the tusks in half and for making the tusks ready for reading. This study was funded by the Danish Ministry of the Environment Program DANCEA (M 112-00265; Danish Co-operation for Environment in the Arctic) and the Greenland Institute of Natural Resources. E.G. and M.P.H.-J. were supported by the Independent Research Fund Denmark case 0135-00228B. R. Dietz designed the study. E.G. C.S. M.P.H.-J. A.A. P.A. R. Drimmie, and R. Dietz provided samples or laboratory analysis; J.-P.D. performed data analysis, with support from R. Dietz and F.F.R.; and J.-P.D. and R. Dietz generated figures and tables. J.-P.D. and R. Dietz drafted the manuscript. All authors were involved in the interpretation of results and writing of the final manuscript. The authors declare no competing interests. Funding Information: Local hunters from Avanersuaq and Uummannaq are acknowledged for providing the narwhal tusks taken during their aboriginal hunt. Jeppe Møhl was responsible for cutting the tusks in half and for making the tusks ready for reading. This study was funded by the Danish Ministry of the Environment Program DANCEA ( M 112-00265 ; Danish Co-operation for Environment in the Arctic) and the Greenland Institute of Natural Resources . E.G. and M.P.H.-J. were supported by the Independent Research Fund Denmark case 0135-00228B . CENPERMOA[2021]

PY - 2021

Y1 - 2021

N2 - The ability of animals to respond to changes in their environment is critical to their persistence. In the Arctic, climate change and mercury exposure are two of the most important environmental threats for top predators.1–3 Rapid warming is causing precipitous sea-ice loss, with consequences on the distribution, composition, and dietary ecology of species4–7 and, thus, exposure to food-borne mercury.8 Current understanding of global change and pollution impacts on Arctic wildlife relies on single-time-point individual data representing a snapshot in time. These data often lack comprehensive temporal resolution and overlook 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 biogeochemical profiles, allowing for investigations of climate-induced dietary changes and contaminant trends. Using temporal patterns of stable isotopes (δ13C and δ15N) and mercury concentrations in annually deposited dentine growth layer groups in 10 tusks from Northwest Greenland (1962–2010), we show surprising plasticity in narwhal feeding ecology likely resulting from climate-induced changes in sea-ice cover, biological communities, and narwhal migration. Dietary changes consequently impacted mercury exposure primarily through trophic magnification effects. Mercury increased log-linearly over the study period, albeit with an unexpected rise in recent years, likely caused by increased emissions and/or greater bioavailability in a warmer, ice-free Arctic. Our findings are consistent with an emerging pattern in the Arctic of reduced sea-ice leading to changes in the migration, habitat use, food web, and contaminant exposure in Arctic top predators.

AB - The ability of animals to respond to changes in their environment is critical to their persistence. In the Arctic, climate change and mercury exposure are two of the most important environmental threats for top predators.1–3 Rapid warming is causing precipitous sea-ice loss, with consequences on the distribution, composition, and dietary ecology of species4–7 and, thus, exposure to food-borne mercury.8 Current understanding of global change and pollution impacts on Arctic wildlife relies on single-time-point individual data representing a snapshot in time. These data often lack comprehensive temporal resolution and overlook 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 biogeochemical profiles, allowing for investigations of climate-induced dietary changes and contaminant trends. Using temporal patterns of stable isotopes (δ13C and δ15N) and mercury concentrations in annually deposited dentine growth layer groups in 10 tusks from Northwest Greenland (1962–2010), we show surprising plasticity in narwhal feeding ecology likely resulting from climate-induced changes in sea-ice cover, biological communities, and narwhal migration. Dietary changes consequently impacted mercury exposure primarily through trophic magnification effects. Mercury increased log-linearly over the study period, albeit with an unexpected rise in recent years, likely caused by increased emissions and/or greater bioavailability in a warmer, ice-free Arctic. Our findings are consistent with an emerging pattern in the Arctic of reduced sea-ice leading to changes in the migration, habitat use, food web, and contaminant exposure in Arctic top predators.

KW - biogeochemical markers

KW - climate change

KW - feeding ecology

KW - mercury

KW - narwhal

KW - stable isotopes

KW - temporal trend

KW - tusk

U2 - 10.1016/j.cub.2021.02.018

DO - 10.1016/j.cub.2021.02.018

M3 - Journal article

C2 - 33705717

AN - SCOPUS:85105317106

VL - 31

SP - 2012-2019.e2

JO - Current Biology

JF - Current Biology

SN - 0960-9822

IS - 9

ER -