Comparison of mesozooplankton communities at three shallow seamounts in the South West Indian Ocean - Université de Montpellier Accéder directement au contenu
Article Dans Une Revue Deep Sea Research Part II: Topical Studies in Oceanography Année : 2020

Comparison of mesozooplankton communities at three shallow seamounts in the South West Indian Ocean

Margaux Noyon
  • Fonction : Auteur
Zo Rasoloarijao
  • Fonction : Auteur
Jenny Huggett
  • Fonction : Auteur
Michael Roberts
  • Fonction : Auteur

Résumé

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.

Dates et versions

hal-03411055 , version 1 (02-11-2021)

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Citer

Margaux Noyon, Zo Rasoloarijao, Jenny Huggett, Jean-Francois Ternon, Michael Roberts. Comparison of mesozooplankton communities at three shallow seamounts in the South West Indian Ocean. Deep Sea Research Part II: Topical Studies in Oceanography, 2020, 176, pp.104759. ⟨10.1016/j.dsr2.2020.104759⟩. ⟨hal-03411055⟩
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