Saint-Denis-d'Oléron, France
Saint-Denis-d'Oléron, France

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Mora C.,Dalhousie University | Aburto-Oropeza O.,University of California at San Diego | Ayala-Bocos A.,Autonomous University of Baja California Sur | Ayotte P.M.,University of Hawaii at Manoa | And 62 more authors.
PLoS Biology | Year: 2011

Difficulties in scaling up theoretical and experimental results have raised controversy over the consequences of biodiversity loss for the functioning of natural ecosystems. Using a global survey of reef fish assemblages, we show that in contrast to previous theoretical and experimental studies, ecosystem functioning (as measured by standing biomass) scales in a non-saturating manner with biodiversity (as measured by species and functional richness) in this ecosystem. Our field study also shows a significant and negative interaction between human population density and biodiversity on ecosystem functioning (i.e., for the same human density there were larger reductions in standing biomass at more diverse reefs). Human effects were found to be related to fishing, coastal development, and land use stressors, and currently affect over 75% of the world's coral reefs. Our results indicate that the consequences of biodiversity loss in coral reefs have been considerably underestimated based on existing knowledge and that reef fish assemblages, particularly the most diverse, are greatly vulnerable to the expansion and intensity of anthropogenic stressors in coastal areas. © 2011 Mora et al.


Crochelet E.,Parc Technologique University | Crochelet E.,IRD Montpellier | Chabanet P.,Parc Technologique University | Pothin K.,Reserve Naturelle Marine de la Reunion | And 6 more authors.
Ocean and Coastal Management | Year: 2013

The pelagic larval period is probably the least understood life stage of reef fish, yet the processes of larval dispersal and settlement exert a strong influence on the persistence of reef fish populations. A thorough understanding of these processes is essential to determining whether distant populations are connected and how to adapt management plans to patterns in connectivity. Managers may erroneously assume that local populations are isolated when they are actually replenished by distant reefs beyond their jurisdiction. Researchers increasingly rely on numerical hydrodynamic models that simulate the spatiotemporal dispersal of larvae by ocean currents to elucidate these connections and guide marine spatial planners, yet relatively little work has been done to validate these models with empirical data. In this study, we tested a dispersal simulation model against in situ observations of young post-larval fish to investigate a whether larvae settling at La Réunion (in the western Indian Ocean) might have originated at Mauritius, 200km distant. First, we collected post larval specimens of honeycomb grouper (Epinephelus merra) shortly after an episodic mass settlement that occurred in 2002 at La Réunion. Using sclerochronology, we established the age of the fish from their otoliths. Finally, we simulated dispersal of larvae from La Réunion, Mauritius, and other reefs in the region by ocean currents using a 2D Eulerian advection-diffusion model driven by current velocities derived from satellite remote sensing. The simulation suggested that larvae spawned at La Réunion were carried away from the island while larvae spawned at Mauritius were carried to La Réunion. The otolith-derived ages of the fish were compatible with this hypothesis, when we accounted for the time required for larvae to drift from Mauritius to La Réunion. The combined results suggest a dispersal connection from Mauritius to La Réunion. To best maintain populations of adult reef fish at La Réunion, managers should protect stocks spawning at Mauritius. Although more study is needed to characterize patterns of regional connectivity and account for seasonal and inter-annual variations in these patterns, the example presented here demonstrates the possibility of distant connections in the western Indian Ocean. We urge managers in the region to look beyond their own jurisdictions, view their jurisdictions as part of a connected network, and undertake a collaborative approach to protecting the network as a whole. © 2013 Elsevier Ltd.


Riou A.,IRD Montpellier | Bareille G.,French National Center for Scientific Research | Morat F.,IRSTEA | Pothin K.,Reserve Naturelle Marine de la Reunion | And 2 more authors.
Fisheries Research | Year: 2016

Due to the relative geographical isolation of Reunion Island the grouper Epinephelus merra is assumed to be self-recruited but almost nothing is known about its larval history. We used elemental composition of the otoliths (Ba, Sr, Mn, Mg, Na) of fifty-eight one year-old groupers collected from four main coral reefs on the west coast of Reunion Island, to determine environmental variations during their early life history. Hierarchical clustering analysis of the otolith chemical composition of core and early larval phase, allowed the identification of three groups of larvae. Larvae from the first group (cluster 1) were born and dispersed in Ba-enriched water bodies, while the second and third groups included larvae that had crossed Ba-poor water masses. Larvae of group 1 were primarily found in the southern sector (74%) decreasing northward, while group 3 were more abundant in the northern sector (56%) and cluster 2 showed a scattered distribution. Such opposite spatial distributions might suggest that clusters 1 and 3 originated from opposite dispersal kernels, south and north respectively. It is possible however that larvae from both groups came from the same spawning ground but represented different cohorts that experienced changing geochemical conditions either at the spawning site or within the surrounding pelagic environment, over the course of the breeding season. Both scenarios on the origin and dispersion may thus suggest significant influence of hydrographic features causing or preventing larvae from becoming displaced far from their natal area. © 2016 Elsevier B.V.


Muths D.,French Research Institute for Exploitation of the Sea | Tessier E.,Reserve Naturelle Marine de la Reunion | Gouws G.,South African Institute For Aquatic Biodiversity | Craig M.,University of Puerto Rico at Mayaguez | And 4 more authors.
Marine Ecology Progress Series | Year: 2011

The reef fish Myripristis berndti (Jordan & Everman 1903) is a pantropical species. A genetic analysis was conducted on 353 individuals from 10 localities distributed across the SW Indian Ocean (SWIO) in order to determine patterns of connectivity in the SWIO. Both the mtDNA sequences (711-bp cytochrome b sequences) and the microsatellites (8 newly developed loci) reveal spatial patterns of differentiation within the SWIO. There is, however, a discrepancy between the structure observed with each kind of marker. MtDNA revealed that 3 peripheral populations (NW Kenya, SE Reunion, and SW Europa) were isolated from the 7 more central populations, which form a more densely connected population network, while microsatellite data indicated a more restricted connectivity with significant differentiation between most pairs of localities. Higher genetic differences between Reunion and Europa were found, which might be explained by geography and isolation by distance pattern. In contrast, the genetic signature of Kenya-the most divergent locality identified by mtDNA basis but not with microsatellite-was probably the consequence of a particular colonisation history. These results indicate a much more restricted connectivity than previously thought for this species. © 2011 Inter-Research.


Muths D.,French Research Institute for Exploitation of the Sea | Gouws G.,Reserve Naturelle Marine de La Reunion | Mwale M.,Reserve Naturelle Marine de La Reunion | Tessier E.,South African Institute For Aquatic Biodiversity | Bourjea J.,French Research Institute for Exploitation of the Sea
Canadian Journal of Fisheries and Aquatic Sciences | Year: 2012

Examining the genetic structure of species allows an estimate of the level of evolutionary connectivity between localities; this information is important for marine biodiversity protection, in particular, for the delineation of marine protected areas. In this context, a total of 601 Lutjanus kasmira (Forsskål, 1775) were sampled in 16 localities of the western Indian Ocean and analyzed with both mitochondrial cytochrome b sequencing and eight microsatellite loci genotyping. Both genetic markers indicate that differentiation was not significant even between samples separated by more than 4000 km. This absence of genetic differentiation among samples was favored by ecological plasticity of the species and is now ensured by resultant high levels of dispersal. Nevertheless, some significant genetic structure was detected for the areas of Mauritius and Moroni, as well as within populations in all localities, which will have to be explained by additional studies on local processes.


Muths D.,French Research Institute for Exploitation of the Sea | Tessier E.,Reserve Naturelle Marine de La Reunion | Bourjea J.,French Research Institute for Exploitation of the Sea
Marine Ecology | Year: 2015

The reef fauna connectivity of the West Indian Ocean (WIO) is one of the least studied globally. Here we use genetic analyses of the grouper Epinephelus merra (Bloch 1793) to determine patterns of connectivity and to identify barriers to dispersal in this WIO marine area. Phylogeographic and population-level analyses were conducted on cytochrome b sequences and microsatellites (13 loci) from 557 individuals sampled in 15 localities distributed across the West Indian Ocean. Additional samples from the Pacific Ocean were used to benchmark the WIO population structure. The high level of divergence revealed between Indian and Pacific localities (of about 4.5% in sequences) might be the signature of the major tectonic and climatic changes operating at the Plio-Pleistocene transition, congruently with numerous examples of Indo-Pacific speciation. In comparison, the E. merra sequences from the Indian Ocean constitute a monophyletic clade with a low average genetic distance (d < 0.5%). However both genetic markers indicated some structure within this ocean. The main structure revealed was the isolation of the Maldives from the WIO localities (a different group signature identified by clustering analysis, great values of differentiation). Both marker types reveal further significant structure within the WIO, mainly the isolation of the Mascarene Islands (significant AMOVA and isolation-by-distance patterns) and some patchy structure between the northernmost localities and within the Mozambique Channel. The WIO genetic structure of E. merra appeared congruent with main biogeographic boundaries and oceanographic currents. © 2014 Blackwell Verlag GmbH.

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