Stable isotope patterns of mesopelagic communities over two shallow seamounts of the south-western Indian Ocean

Type Article
Date 2020-06
Language English
Author(s) Annasawmy Pavanee1, 2, Cherel Yves3, Romanov Evgeny V.4, Le Loch Francois5, Ménard Frédéric6, Ternon Jean-Francois1, Marsac Francis1, 2
Affiliation(s) 1 : MARBEC, IRD, Univ Montpellier, CNRS, Ifremer, Sète, France
2 : Department of Biological Sciences and Marine Research Institute/ICEMASA, University of Cape Town, Cape Town, South Africa
3 : Centre d’Etudes Biologiques de Chizé (CEBC), UMR7372 du CNRS- La Rochelle Université, Villiers-en-Bois, France
4 : Centre technique d'appui à la pêche réunionnaise (CAP RUN - CITEB), Île de la Réunion, France
5 : IRD, Univ Brest, CNRS, Ifremer, LEMAR, IUEM, F-29280, Plouzane, France
6 : Aix Marseille Univ, Université de Toulon, CNRS, IRD, MIO, UM110, Marseille, France
Source Deep-sea Research Part Ii-topical Studies In Oceanography (0967-0645) (Elsevier BV), 2020-06 , Vol. 176 , P. 104804 (15p.)
DOI 10.1016/j.dsr2.2020.104804
WOS© Times Cited 3
Keyword(s) Micronekton, Crustaceans, Fish, delta C-13, delta N-15, Trophic level, Squid
Abstract

The stable carbon (δ13C) and nitrogen (δ15N) isotope values of soft tissues of micronekton (crustaceans, squid, mesopelagic fish) and zooplankton were measured from organisms collected on the RV Antea at two seamounts located in the south-western Indian Ocean: La Pérouse (summit depth ∼60 m) and “MAD-Ridge” (thus named in this study; summit depth ∼240 m). Surface particulate organic matter (POM-Surf) showed higher δ13C at the more productive MAD-Ridge than at the oligotrophic La Pérouse seamount. Particulate organic matter and zooplankton were depleted in 15N at La Pérouse pinnacle compared with MAD-Ridge. Gelatinous organisms and crustaceans occupied the lowest and intermediate trophic levels (TL ∼2 and 3 respectively) at both seamounts. Mesopelagic fish and smaller-sized squid sampled at both seamounts occupied TL ∼3 to 4, whereas the large nektonic squid, Ommastrephes bartramii, collected at MAD-Ridge only, exhibited a TL of ∼5. The δ15N values of common open-water mesopelagic taxa were strongly influenced by specimen size and feeding habits at both seamounts, with an increase in δ15N values with increasing size. Carnivorous fish species sampled exclusively over the seamounts’ flanks and summits exhibited TL values of ∼4, irrespective of their wide size ranges. The work could not demonstrate any differences in δ15N values of mesopelagic fish between the seamounts and the surrounding oceanic areas. The study segregated clusters of mesopelagic organisms according to their δ13C and δ15N values, with variations in stable isotope values reflecting a complex range of processes possibly linked to productivity as well as biological and ecological traits of the species (size and feeding mode).

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Annasawmy Pavanee, Cherel Yves, Romanov Evgeny V., Le Loch Francois, Ménard Frédéric, Ternon Jean-Francois, Marsac Francis (2020). Stable isotope patterns of mesopelagic communities over two shallow seamounts of the south-western Indian Ocean. Deep-sea Research Part Ii-topical Studies In Oceanography, 176, 104804 (15p.). Publisher's official version : https://doi.org/10.1016/j.dsr2.2020.104804 , Open Access version : https://archimer.ifremer.fr/doc/00632/74429/