The Twilight Zone as a Major Foraging Habitat and Mercury Source for the Great White Shark

Type Article
Date 2020-12
Language English
Author(s) Le Croizier Gaël1, Lorrain Anne2, Sonke Jeroen E.1, Hoyos-Padilla E. Mauricio3, 4, Galván-Magaña Felipe5, Santana-Morales Omar6, Aquino-Baleytó Marc3, 5, Becerril-García Edgar E.3, 5, Muntaner-López Gádor3, 5, Ketchum James3, Block Barbara7, Carlisle Aaron8, Jorgensen Salvador J.9, Besnard Lucien2, Jung Armelle10, Schaal Gauthier2, Point David1
Affiliation(s) 1 : UMR Géosciences Environnement Toulouse (GET), Observatoire Midi Pyrénées (OMP), 14 avenue Edouard Belin, 31400 Toulouse, France
2 : Univ Brest, CNRS, Ifremer, LEMAR, 29280 Plouzané, France
3 : Pelagios-Kakunjá A.C., Sinaloa 1540, Col. Las Garzas, 23070 La Paz, Baja California Sur, México
4 : Fins Attached: Marine Research and Conservation, 19675 Still Glen Drive, Colorado Springs, Colorado 80908, United States
5 : Instituto Politécnico Nacional, Centro Interdisciplinario de Ciencias Marinas, Av. IPN s/n., 23096 La Paz, Baja California Sur, México
6 : ECOCIMATI A.C., 22800 Ensenada, Baja California, Mexico
7 : Hopkins Marine Station, Stanford University, Pacific Grove, California 93950, United States
8 : School of Marine Science and Policy, University of Delaware, Lewes, Delaware 19958, United States
9 : Institute of Marine Sciences, University of California, Santa Cruz, Santa Cruz, California 95064, United States
10 : Des Requins et Des Hommes (DRDH), BLP/Technopole Brest-Iroise, 15 rue Dumont d’Urville, Plouzané 29860, France
Source Environmental Science & Technology (0013-936X) (American Chemical Society (ACS)), 2020-12 , Vol. 54 , N. 24 , P. 15872-15882
DOI 10.1021/acs.est.0c05621
WOS© Times Cited 16

The twilight zone contains the largest biomass of the world’s ocean. Identifying its role in the trophic supply and contaminant exposure of marine megafauna constitutes a critical challenge in the context of global change. The white shark (Carcharodon carcharias) is a threatened species with some of the highest concentrations of neurotoxin methylmercury (MeHg) among marine top predators. Large white sharks migrate seasonally from coastal habitats, where they primarily forage on pinnipeds, to oceanic offshore habitats. Tagging studies suggest that while offshore, white sharks may forage at depth on mesopelagic species, yet no biochemical evidence exists. Here, we used mercury isotopic composition to assess the dietary origin of MeHg contamination in white sharks from the Northeast Pacific Ocean. We estimated that a minimum of 72% of the MeHg accumulated by white sharks originates from the consumption of mesopelagic prey, while a maximum of 25% derives from pinnipeds. In addition to highlighting the potential of mercury isotopes to decipher the complex ecological cycle of marine predators, our study provides evidence that the twilight zone constitutes a crucial foraging habitat for these large predators, which had been suspected for over a decade. Climate change is predicted to expand the production of mesopelagic MeHg and modify the mesopelagic biomass globally. Considering the pivotal role of the twilight zone is therefore essential to better predict both MeHg exposure and trophic supply to white sharks, and effectively protect these key vulnerable predators.

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Le Croizier Gaël, Lorrain Anne, Sonke Jeroen E., Hoyos-Padilla E. Mauricio, Galván-Magaña Felipe, Santana-Morales Omar, Aquino-Baleytó Marc, Becerril-García Edgar E., Muntaner-López Gádor, Ketchum James, Block Barbara, Carlisle Aaron, Jorgensen Salvador J., Besnard Lucien, Jung Armelle, Schaal Gauthier, Point David (2020). The Twilight Zone as a Major Foraging Habitat and Mercury Source for the Great White Shark. Environmental Science & Technology, 54(24), 15872-15882. Publisher's official version : , Open Access version :