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

Type Article
Date 2020-06
Language English
Author(s) Noyon Margaux1, Rasoloarijao Zo1, Huggett Jenny3, 4, Ternon Jean-Francois5, Roberts Michael1, 2
Affiliation(s) 1 : UK-SA NRF/DST Bilateral Research Chair: Ocean Sciences & Marine Food Security, Nelson Mandela University, Port Elizabeth, South Africa
2 : National Oceanography Centre, Southampton, United Kingdom
3 : Oceans and Coastal Research, Department of Environmental Affairs, Private Bag X4390, Cape Town, 8000, South Africa
4 : Marine Research Institute, Department of Biological Sciences, University of Cape Town, Private Bag X3, Rondebosch, 7701, Cape Town, South Africa
5 : MARBEC, Univ. Montpellier, CNRS, Ifremer, IRD, Sète, France
Source Deep-sea Research Part Ii-topical Studies In Oceanography (0967-0645) (Elsevier BV), 2020-06 , Vol. 176 , P. 104759 (17p.)
DOI 10.1016/j.dsr2.2020.104759
WOS© Times Cited 4
Keyword(s) Normalised biovolume size spectrum (NBSS), Mesoscale eddies, Topography, Oligotrophic environment, Pelagic ecology
Abstract

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 (60m, 240m and 18m deep) in the South West Indian Ocean, along a latitudinal gradient (19°S, 27°S and 33°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 Pérouse 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 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.

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Noyon Margaux, Rasoloarijao Zo, Huggett Jenny, Ternon Jean-Francois, Roberts Michael (2020). Comparison of mesozooplankton communities at three shallow seamounts in the South West Indian Ocean. Deep-sea Research Part Ii-topical Studies In Oceanography, 176, 104759 (17p.). Publisher's official version : https://doi.org/10.1016/j.dsr2.2020.104759 , Open Access version : https://archimer.ifremer.fr/doc/00609/72157/