Publications des scientifiques de l'IRD

Annasawmy P., Ternon Jean-François, Marsac Francis, Cherel Y., Behagle Nolwenn, Roudaut Gildas, Lebourges Dhaussy Anne, Demarcq Hervé, Moloney C. L., Jaquemet S., Ménard Frédéric. (2018). Micronekton diel migration, community composition and trophic position within two biogeochemical provinces of the South West Indian Ocean : insight from acoustics and stable isotopes. Deep-Sea Research Part I : Oceanographic Research Papers, 138, p. 85-97. ISSN 0967-0637.

Titre du document
Micronekton diel migration, community composition and trophic position within two biogeochemical provinces of the South West Indian Ocean : insight from acoustics and stable isotopes
Année de publication
2018
Type de document
Article référencé dans le Web of Science WOS:000445985100008
Auteurs
Annasawmy P., Ternon Jean-François, Marsac Francis, Cherel Y., Behagle Nolwenn, Roudaut Gildas, Lebourges Dhaussy Anne, Demarcq Hervé, Moloney C. L., Jaquemet S., Ménard Frédéric
Source
Deep-Sea Research Part I : Oceanographic Research Papers, 2018, 138, p. 85-97 ISSN 0967-0637
Spatial distribution, community composition and trophic roles of micronekton (crustaceans, fishes and squids) were investigated in the Indian South Subtropical Gyre (ISSG) province and the East African Coastal province (EAFR), by combining acoustic surveys, mid-water trawls and stable isotope analyses from scientific cruises conducted in 2009 and 2010. Mesopelagic micronekton performed diel vertical migrations in both provinces, from deep (400-740 m) to surface (0-200 m) layers at dusk and in the opposite direction at dawn, with some species migrating below 740 m. The EAFR province was more dynamic than the oligotrophic ISSG province, with enhanced eddy activity and enhanced yearly productivity. The active enrichment mechanisms in the EAFR, in terms of available primary production, led to high micronekton acoustic density (as a proxy of micronekton abundance) and large micronekton weight and abundance estimates from trawl data. Particulate organic matter in the EAFR exhibited greater enrichment in C-13 and N-15 compared to the ISSG and, consequently, tissues of selected micronekton organisms in the EAFR were more enriched in N-15 (higher delta N-15 values). In both provinces, micronekton encompassed a wide range of isotopic niches, with large overlaps between species. Micronekton and swordfish in the EAFR had an overlapping range of delta N-15 values, contrasting with the ISSG province where swordfish were two trophic levels higher than the sampled micronekton. Our results provide some evidence that the combined action of riverine input and the dynamics of eddies might influence productivity in the EAFR, and hence the abundance of micronekton and the enrichment of tissues in N-15, compared to the oligotrophic ISSG province.
Plan de classement
Ecologie, systèmes aquatiques [036]
Description Géographique
OCEAN INDIEN SUD OUEST
Localisation
Fonds IRD [F B010074098]
Identifiant IRD
fdi:010074098
Contact