title: Trophic relationships between metazooplankton communities and their plankton food sources in the Iles Eparses (Western Indian Ocean).
abstract: Coral reef and atoll lagoons are among the most diversified marine ecosystems but also the most affected by the combined effects of climate change and human activities. The Iles Eparses (Scattered Islands) in the Western Indian Ocean have been little affected by human pressure and can be considered to be "pristine" ecosystems. Metazooplankton plays a major role in the functioning and productivity of aquatic ecosystems, and this study was undertaken: (i) to determine the spatial abundance, distribution and species composition of metazooplankton, (ii) to assess the effect of metazooplankton grazing on pico- and nanophytoplankton and (iii) to analyze the trophic positions of metazooplankton by using the stable isotope signatures of a wide variety of taxa and particulate organic matter from the Iles Eparses and Mayotte. Tromelin Island (which is not located in the Mozambique Channel) had the lowest metazooplankton abundance with no cyanobacteria Trichodesmium spp. or mollusks (pteropods) presence, and with δ(15)N signatures of organisms that were higher than for the islands in the Mozambique Channel. Trichodesmium spp. was found in the Mozambique Channel and the plankton food web was probably based preferentially on these cyanobacteria with lower δ(15)N signatures indicating direct or indirect trophic transfer of diazotrophic nitrogen to metazooplankton. Three of the islands were distinct: Europa had the highest proportion of copepods, with oithonids being dominant, which is typical of rich mangrove systems, while Juan de Nova and Mayotte seemed to be the sites most affected by human activity with a high abundance of appendicularians and distinct particulate organic matter ∂(13)C signatures. Grazing experiments showed that food could be a limiting factor for metazooplankton in the Iles Eparses. However, the effect of metazooplankton grazing on phytoplankton appeared to be very low (0.01-2.32% of the total phytoplankton per day).
authors.affiliation: Littoral, Environnement et Sociétés (LIENSs) UMR 7266 CNRS, Université de La Rochelle, 2 rue Olympe de Gouges, 17000, La Rochelle, France. Electronic address: cdupuy@univ-lr.fr.
authors.forename: Christine
authors.initials: C
authors.lastname: Dupuy
authors.affiliation: Mediterranean Institute of Oceanography, Aix Marseille Université, CNRS, Université de Toulon, IRD, MIO UM 110, 13288, Marseille, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Pagano
authors.affiliation: MARBEC, UMR 248, IRD, Ifremer, Université Montpellier, CNRS, Université Montpellier, Place E. Bataillon, Case 093, 34095, Montpellier Cedex 5, France.
authors.forename: Patrice
authors.initials: P
authors.lastname: Got
authors.affiliation: CARRTEL, UMR 42, INRA, 75 avenue de Corzent, 74203, Thonon-les-bains, France.
authors.forename: Isabelle
authors.initials: I
authors.lastname: Domaizon
authors.affiliation: Littoral, Environnement et Sociétés (LIENSs) UMR 7266 CNRS, Université de La Rochelle, 2 rue Olympe de Gouges, 17000, La Rochelle, France.
authors.forename: Alexis
authors.initials: A
authors.lastname: Chappuis
authors.affiliation: Mediterranean Institute of Oceanography, Aix Marseille Université, CNRS, Université de Toulon, IRD, MIO UM 110, 13288, Marseille, France.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Marchessaux
authors.affiliation: MARBEC, UMR 248, IRD, Ifremer, Université Montpellier, CNRS, Université Montpellier, Place E. Bataillon, Case 093, 34095, Montpellier Cedex 5, France.
authors.forename: Marc
authors.initials: M
authors.lastname: Bouvy
mesh_terms: D000818:Animals; D020387:Food Chain; D019156:Indian Ocean; D062312:Islands; D010933:Plankton / Q000502:physiology*; D015048:Zooplankton / Q000502:physiology*
keywords: Feeding ecology; Grazing effect; Iles Eparses; Mayotte; Metazooplankton; Spatial distribution