Connectivity between seamounts and coastal ecosystems in the Southwestern Indian Ocean

Type Article
Date 2020-06
Language English
Author(s) Crochelet Estelle1, 2, Barrier Nicolas3, 4, Andrello Marco3, 4, Marsac Francis3, 4, Spadone Aurélie5, Lett Christophe3, 4
Affiliation(s) 1 : ARBRE - Agence de Recherche pour la Biodiversité à la Réunion, 34 avenue de la Grande Ourse, 97434, Saint-Gilles, La Réunion, France
2 : IRD / ESPACE-DEV (UMR 228), Parc Technologique Universitaire, 2 rue Joseph Wetzell, CS 41 095, 97495, Sainte Clotilde Cedex, La Réunion, France
3 : Institut de Recherche pour le Développement (IRD), Sète, France
4 : MARBEC, Univ Montpellier, CNRS, Ifremer, IRD, Sète, France
5 : IUCN – International Union for Conservation of Nature, Gland, Switzerland
Source Deep-sea Research Part Ii-topical Studies In Oceanography (0967-0645) (Elsevier BV), 2020-06 , Vol. 176 , P. 104774 (18p.)
DOI 10.1016/j.dsr2.2020.104774
WOS© Times Cited 5
Keyword(s) Seamounts, Connectivity, Larval duration, Larval drift, Lagrangian modelling, Biophysical model, Surface drifters, Southwestern indian ocean, Ichthyop
Abstract

Understanding larval connectivity patterns is critical for marine spatial planning, particularly for designing marine protected areas and managing fisheries. Patterns of larval dispersal and connectivity can be inferred from numerical transport models at large spatial and temporal scales. We assess model-based connectivity patterns between seamounts of the Southwestern Indian Ocean (SWIO) and the coastal ecosystems of Mauritius, La Réunion, Madagascar, Mozambique and South Africa, with emphasis on three shallow seamounts (La Pérouse [LP], MAD-Ridge [MR] and Walters Shoal [WS]). Using drifter trajectory and a Lagrangian model of ichthyoplankton dispersal, we show that larvae can undertake very long dispersion, with larval distances increasing with pelagic larval duration (PLD). There are three groups of greater connectivity: the region between the eastern coast of Madagascar, Mauritius and La Réunion islands; the seamounts of the South West Indian Ridge; and the pair formed by WS and a nearby un-named seamount. Connectivity between these three groups is evident only for the longest PLD examined (360 d). Connectivity from seamounts to coastal ecosystems is weak, with a maximum of 2% of larvae originating from seamounts reaching coastal ecosystems. Local retention at the three focal seamounts (LP, MR and WS) peaks at about 11% for the shortest PLD considered (15 d) at the most retentive seamount (WS) and decreases sharply with increasing PLD. Information on PLD and age of larvae collected at MR and LP are used to assess their putative origin. These larvae are likely self-recruits but it is also plausible that they immigrate from nearby coastal sites, i.e. the southern coast of Madagascar for MR and the islands of La Réunion and Mauritius for LP.

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Crochelet Estelle, Barrier Nicolas, Andrello Marco, Marsac Francis, Spadone Aurélie, Lett Christophe (2020). Connectivity between seamounts and coastal ecosystems in the Southwestern Indian Ocean. Deep-sea Research Part Ii-topical Studies In Oceanography, 176, 104774 (18p.). Publisher's official version : https://doi.org/10.1016/j.dsr2.2020.104774 , Open Access version : https://archimer.ifremer.fr/doc/00613/72461/