Annasawmy P. auteur aut IRD Ternon Jean-François auteur aut IRD Marsac Francis auteur aut IRD Cherel Y. auteur aut IRD Behagle Nolwenn auteur aut IRD Roudaut Gildas auteur aut IRD Lebourges Dhaussy Anne auteur aut IRD Demarcq Hervé auteur aut IRD Moloney C. L. auteur aut IRD Jaquemet S. auteur aut IRD Ménard Frédéric auteur aut IRD text journalArticle eng text/pdf born digital access 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. specialized Micronekton Diel vertical migration Indian South Subtropical Gyre East African Coastal province Trophic level OCEAN INDIEN SUD OUEST 036 138 85-97 2018 0967-0637 https://www.documentation.ird.fr/hor/fdi:010074098 10.1016/j.dsr.2018.07.002 0967-0637 [F B010074098] https://www.documentation.ird.fr/hor/fdi:010074098 https://www.documentation.ird.fr/intranet/publi/2018/10/010074098.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2018-11-07 2023-07-11 fdi:010074098 fre