Noyon M. auteur aut IRD Rasoloarijao Z. auteur aut IRD Huggett J. auteur aut IRD Ternon Jean-François auteur aut IRD Roberts M. auteur aut IRD text journalArticle eng text/pdf born digital access Seamounts are recognised as hotspots of biodiversity, attracting large numbers of top predators, but the underlying mechanisms are still unclear. We studied mesozooplankton abundance and size distribution at three shallow seamounts (60 m, 240 m and 18 m deep) in the South West Indian Ocean, along a latitudinal gradient (19 degrees S, 27 degrees S and 33 degrees S). Samples were analysed using a ZooScan, allowing the use of a size-based approach. Differences were observed between seamount areas, but overall zooplankton communities did not seem to be affected by the changes in topography. Only in the lee of La Perouse seamount was the zooplankton community slightly more concentrated than upstream, suggesting that zooplankton were flushed downstream of the seamount. The southernmost and shallowest seamount, Walters Shoal, had low abundance and its size spectrum differed greatly from the two other seamounts further north. These differences were attributed to seasonality and mesozooplankton population dynamics, whereas the other two seamounts exhibited a more "typical" oligotrophic pelagic ecosystem, at equilibrium and dominated by small organisms. At the time of sampling, the unnamed seamount south of Madagascar was influenced by a mesoscale dipole that impacted the zooplankton distribution, potentially masking any seamount effect. The normalised biomass size spectrum approach contributed to a better understanding of the ecosystem dynamics (i.e. equilibrium vs. non-steady state) but revealed little variability within a stable oligotrophic environment. specialized Normalised biovolume size spectrum (NBSS) Mesoscale eddies Topography Oligotrophic environment Pelagic ecology OCEAN INDIEN 030 034 036 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 176 No spécial art. 104759 [17 ] 2020 0967-0645 https://www.documentation.ird.fr/hor/fdi:010079448 10.1016/j.dsr2.2020.104759 0967-0645 [F B010079448] https://www.documentation.ird.fr/hor/fdi:010079448 https://www.documentation.ird.fr/intranet/publi/2020/08/010079448.pdf Accès réservé (Intranet de l'IRD) IRD - Base Horizon / Pleins textes 2020-09-17 2025-02-24 fdi:010079448 fre