Finding mesopelagic prey in a changing Southern Ocean

• Published in: Scientific Reports
• Main Authors: Mcmahon, Clive R., Hindell, Mark A., Charrassin, Jean-Benoit, Corney, Stuart, Guinet, Christophe, Harcourt, Robert G., Jonsen, Ian D., Trebilco, Rowan, Williams, Guy Darvall, Bestley, Sophie
• Other Authors: University of Sydney Institute of Marine Science (USIMS), The University of Sydney, Institute for Marine and Antarctic Studies Hobart (IMAS), University of Tasmania Hobart, Australia (UTAS), Processus et interactions de fine échelle océanique (PROTEO), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales Toulouse (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Antarctic Climate and Ecosystems Cooperative Research Centre (ACE-CRC), Centre d'Études Biologiques de Chizé - UMR 7372 (CEBC), Institut National de la Recherche Agronomique (INRA)-La Rochelle Université (ULR)-Centre National de la Recherche Scientifique (CNRS), Macquarie University Sydney, French Polar Institute (program 109: PI. H. Weimerskirch and 1201: PI. C. Gilbert and C. Guinet), the SNO-MEMO CNES-TOSCA
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2019
• Subjects: [SDE]Environmental Sciences; Antarctic; Indian; Kerguelen; Southern Ocean; Antarc*; Elephant Seal; Southern Elephant Seal
• Online Access: https://hal.science/hal-02417330; https://hal.science/hal-02417330/document; https://hal.science/hal-02417330/file/s41598-019-55152-4.pdf; https://doi.org/10.1038/s41598-019-55152-4

International audience Mesopelagic fish and squid occupy ocean depths extending below the photic zone and their verticalmigrations represent a massive pathway moving energy and carbon through the water column.Their spatio-temporal distribution is however, difficult to map across remote regions particularly thevast Southern Ocean. This represents a key gap in understanding biogeochemical processes, marineecosystem structure, and how changing ocean conditions will affect marine predators, which dependupon mesopelagic prey. We infer mesopelagic prey vertical distribution and relative abundance inthe Indian sector of the Southern Ocean (20° to 130°E) with a novel approach using predator-derivedindices. Fourteen years of southern elephant seal tracking and dive data, from the open ocean betweenthe Antarctic Polar Front and the southern Antarctic Circumpolar Current front, clearly show that thevertical distribution of mesopelagic prey is influenced by the physical hydrographic processes thatstructure their habitat. Mesopelagic prey have a more restricted vertical migration and higher relativeabundance closer to the surface where Circumpolar Deep Water rises to shallower depths. Combiningthese observations with a future projection of Southern Ocean conditions we show that changes in thecoupling of surface and deep waters will potentially redistribute mesopelagic prey. These changes aresmall overall, but show important spatial variability: prey will increase in relative abundance to the eastof the Kerguelen Plateau but decrease to the west. The consequences for deep-diving specialists such aselephant seals and whales over this time scale will likely be minor, but the changes in mesoscale verticalenergy flow have implications for predators that forage within the mesopelagic zone as well as thebroader pelagic ecosystem.