Seamount effect on circulation and distribution of ocean taxa in the vicinity of La Perouse, a shallow seamount in the southwestern Indian Ocean

Seamount effect on circulation and distribution of ocean taxa in the vicinity of La Perouse, a shallow seamount in the southwestern Indian Ocean Marsac Francis auteur aut IRD Annasawmy P. auteur aut IRD Noyon M. auteur aut IRD Demarcq Hervé auteur aut IRD Soria Marc auteur aut IRD Rabearisoa Njaratiana auteur aut IRD Bach Pascal auteur aut IRD Cherel Y. auteur aut IRD Grelet Jacques auteur aut IRD Romanov E. auteur aut IRD text journalArticle eng text/pdf born digital access The La Perouse seamount (60 m depth) has so far been poorly studied despite it being a short distance (160 km) from Reunion Island. As part of the MADRidge project, a multidisciplinary cruise was conducted to evaluate the effect of this shallow seamount on the local hydrology and ecology. Current measurements, temperature and chlorophyll-a profiles, and mesozooplankton and micronekton samples were collected between the summit and 35 km away. Micronekton data were supplemented with stomach content of pelagic top predators as well as fisheries statistics from the domestic longline fleet operating from Reunion. Vertical current profiles revealed distinct patterns between the offshore and seamount-flanked stations, giving evidence of topographical induced flow instabilities, notably on its leeward side (west) relative to the east flank. Distinct patterns in temperature and chlorophyll-a vertical profiles suggest the formation of convergent and divergent circulation cells as a result of the irregular and crescent-like summit topography. Spatial differences in zooplankton abundance were detected with higher biovolumes on the leeward flank. The overall acoustic backscatter for micronekton over the summit was weaker than offshore, but highly concentrated in the upper layer. Albacore tuna and swordfish dominate the longline catch west of Reunion, seemingly in association with a deep (900 m) topographic feature. Yet the largest catch is not directly associated with La Perouse which would be too shallow for top predators to aggregate around in the long term. Enhanced levels of phytoplankton or zooplankton enrichment at La Perouse were not demonstrated in this study, nor was there notable diversity of micronekton species. This might explain the relatively limited importance of this seamount to the tuna fisheries in this region. specialized Bathymetry Mesoscale eddies L-ADCP Mesozooplankton Micronekton Stomach contents Pelagic longline fisheries OCEAN INDIEN REUNION 030 040 034 036 Bio-physical coupling around three shallow seamounts in the South Western Indian Ocean, with regional comparisons based on modelling, remote sensing and observational studies Payne A. ed. edt IRD Roberts M. ed. edt IRD Marsac Francis ed. edt IRD Noyon M. ed. edt IRD Ternon Jean-François ed. edt IRD Deep-Sea Research Part II : Topical Studies in Oceanography 176 No spécial art. 104806 [18 ] 2020 0967-0645 https://www.documentation.ird.fr/hor/fdi:010079446 10.1016/j.dsr2.2020.104806 0967-0645 [F B010079446] https://www.documentation.ird.fr/hor/fdi:010079446 https://www.documentation.ird.fr/intranet/publi/2020/08/010079446.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2020-09-17 2025-02-24 fdi:010079446 fre