CNRS Insular Research Center and Environment Observatory

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CNRS Insular Research Center and Environment Observatory

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Buston P.M.,Boston University | Jones G.P.,James Cook University | Planes S.,CNRS Insular Research Center and Environment Observatory | Thorrold S.R.,Woods Hole Oceanographic Institution
Proceedings of the Royal Society B: Biological Sciences | Year: 2012

A central question of marine ecology is, how far do larvae disperse? Coupled biophysical models predict that the probability of successful dispersal declines as a function of distance between populations. Estimates of genetic isolation-by-distance and self-recruitment provide indirect support for this prediction. Here,we conduct the first direct test of this prediction, using data from the well-studied system of clown anemonefish (Amphiprion percula) at Kimbe Island, in Papua New Guinea. Amphiprion percula live in small breeding groups that inhabit sea anemones. These groups can be thought of as populations within a metapopulation. We use the x- and y-coordinates of each anemone to determine the expected distribution of dispersal distances (the distribution of distances between each and every population in the metapopulation). We use parentage analyses to trace recruits back to parents and determine the observed distribution of dispersal distances. Then, we employ a logistic model to (i) compare the observed and expected dispersal distance distributions and (ii) determine the relationship between the probability of successful dispersal and the distance between populations. The observed and expected dispersal distance distributions are significantly different (p<0.0001). Remarkably, the probability of successful dispersal between populations decreases fivefold over 1 km. This study provides a framework for quantitative investigations of larval dispersal that can be applied to other species. Further, the approach facilitates testing biological and physical hypotheses for the factors influencing larval dispersal in unison, which will advance our understanding of marine population connectivity. © 2011 The Royal Society.

Van Hooidonk R.,National Oceanic and Atmospheric Administration | Maynard J.A.,CNRS Insular Research Center and Environment Observatory | Maynard J.A.,University of North Carolina at Wilmington | Planes S.,CNRS Insular Research Center and Environment Observatory
Nature Climate Change | Year: 2013

Climate-change impacts on coral reefs are expected to include temperature-induced spatially extensive bleaching events. Bleaching causes mortality when temperature stress persists but exposure to bleaching conditions is not expected to be spatially uniform at the regional or global scale. Here we show the first maps of global projections of bleaching conditions based on ensembles of IPCC AR5 (ref.) models forced with the new Representative Concentration Pathways (RCPs). For the three RCPs with larger CO2 emissions (RCP 4.5, 6.0 and 8.5) the onset of annual bleaching conditions is associated with ∼ 510 ppm CO2 equivalent; the median year of all locations is 2040 for the fossil-fuel aggressive RCP 8.5. Spatial patterns in the onset of annual bleaching conditions are similar for each of the RCPs. For RCP 8.5, 26% of reef cells are projected to experience annual bleaching conditions more than 5 years later than the median. Some of these temporary refugia include the western Indian Ocean, Thailand, the southern Great Barrier Reef and central French Polynesia. A reduction in the growth of greenhouse-gas emissions corresponding to the difference between RCP 8.5 and 6.0 delays annual bleaching in ∼ 23% of reef cells more than two decades, which might conceivably increase the potential for these reefs to cope with these changes. © 2013 Macmillan Publishers Limited. All rights reserved.

Sweet M.J.,Northumbria University | Bythell J.C.,Northumbria University | Nugues M.M.,CNRS Insular Research Center and Environment Observatory
PLoS ONE | Year: 2013

Benthic algae are associated with coral death in the form of stress and disease. It's been proposed that they release exudates, which facilitate invasion of potentially pathogenic microbes at the coral-algal interface, resulting in coral disease. However, the original source of these pathogens remains unknown. This study examined the ability of benthic algae to act as reservoirs of coral pathogens by characterizing surface associated microbes associated with major Caribbean and Indo-Pacific algal species/types and by comparing them to potential pathogens of two dominant coral diseases: White Syndrome (WS) in the Indo-Pacific and Yellow Band Disease (YBD) in the Caribbean. Coral and algal sampling was conducted simultaneously at the same sites to avoid spatial effects. Potential pathogens were defined as those absent or rare in healthy corals, increasing in abundance in healthy tissues adjacent to a disease lesion, and dominant in disease lesions. Potentially pathogenic bacteria were detected in both WS and YBD and were also present within the majority of algal species/types (54 and 100% for WS and YBD respectively). Pathogenic ciliates were associated only with WS and not YBD lesions and these were also present in 36% of the Indo-Pacific algal species. Although potential pathogens were associated with many algal species, their presence was inconsistent among replicate algal samples and detection rates were relatively low, suggestive of low density and occurrence. At the community level, coral-associated microbes irrespective of the health of their host differed from algal-associated microbes, supporting that algae and corals have distinctive microbial communities associated with their tissue. We conclude that benthic algae are common reservoirs for a variety of different potential coral pathogens. However, algal-associated microbes alone are unlikely to cause coral death. Initial damage or stress to the coral via other competitive mechanisms is most likely a prerequisite to potential transmission of these pathogens. © 2013 Sweet et al.

Mills S.C.,CNRS Insular Research Center and Environment Observatory
Coral Reefs | Year: 2012

The density-dependent prophylaxis hypothesis predicts that individuals at high density will invest more resources into immune defence than individuals at lower densities as a counter-measure to density-dependent pathogen transmission rates. Evidence has been found for this hypothesis in insects, but not in a non-arthropod taxon. To investigate this hypothesis in the coral-eating crown-of-thorns sea star, Acanthaster planci, density treatments were set up over 21 days, and pathogen infection was simulated with bacterial injection. Five immune responses: amoebocyte count, amoebocyte viability, lysosomal membrane integrity, respiratory burst and peroxidase activity were all upregulated at high density. These results demonstrate that immune investment shows phenotypic plasticity with adult population density in agreement with the density-dependent prophylaxis hypothesis. Here I show that the density-dependent prophylaxis hypothesis is neither dependent on larval density nor restricted to insects, and hence may potentially have important consequences on disease dynamics in any species with widely fluctuating population densities. This is the first demonstration of the density-dependent prophylaxis hypothesis outside arthropods. © 2012 Springer-Verlag.

Mourier J.,CNRS Insular Research Center and Environment Observatory | Planes S.,CNRS Insular Research Center and Environment Observatory
Molecular Ecology | Year: 2013

Conservation of top predators has been emphasized as essential in an ecosystem due to their role in trophic chain regulation. Optimizing conservation strategies for these endangered marine top predators requires direct estimates of breeding patterns and connectivity as these are essential to understanding the population dynamics. There have been some attempts to investigate breeding patterns of reef sharks from litter reconstruction using molecular analyses. However, direct fine-scale migrations of female sharks for parturition as well as connectivity at a medium scale like between islands remain mostly unknown. We used microsatellite DNA markers and a likelihood-based parentage analysis to determine breeding patterns of female blacktip reef sharks in Moorea (Society Islands, French Polynesia). Most females gave birth at their home island but some migrated to specific nursery areas outside the area they are attached to, sometimes going to another island 50 km away across deep ocean. Our analysis also revealed that females migrated to the same nursery for every birthing event. Many offspring showed a high level of inbreeding indicating an overall reduced population size, restricted movements and dispersal, or specific mating behaviour. Females represent the vectors that transport the genes at nursery grounds, and their fidelity should thus define reproductive units. As females seem to be philopatric, males could be the ones dispersing genes between populations. These results highlight the need to conserve coastal zones where female reef sharks seem to exhibit philopatry during the breeding season. © 2012 Blackwell Publishing Ltd.

Collin A.,CNRS Insular Research Center and Environment Observatory | Planes S.,CNRS Insular Research Center and Environment Observatory
Remote Sensing | Year: 2012

The worldwide waning health of coral reefs implies an increasing need for monitoring them at colony scale over large areas. Relaying fieldwork considerably, the remote sensing approach can address this need in offering spectral information relevant for coral health detection with 0.5 m spatial accuracy. We investigated the potential of spectral diversity indices to achieve the discrimination of coral-dominated assemblages and health states from novel satellite imagery (WorldView-2, WV2). Both Equitability's (E) and Pielou's (P) operators were used to quantify the evenness of the corrected visible spectral bands (two times 26 combinations of five bands) corresponding to remotely sensed colonies. Three scleractinian corals (Porites lobata, P. rus and Acropora pulchra) that are primarily involved in Moorea's reef building (French Polynesia) were examined in respect to their health state (healthy or unhealthy, referring to both bleached and dead coral, hereinafter). Using four classifiers, we showed that the Support Vector Machine (SVM) greatly discerned among the six coral classes based upon the five WV2 spectral bands (93%), thus surpassing the classification issued from the three traditionally used bands (80%). Coupling the WV2 dataset with E green-red, E yellow-red or E" coastal"-blue-green allowed the SVM performance to attain 96%. On the other hand, adding the E "coastal"-blue to the WV2-dataset contributed to a substantially increase of the classification accuracy derived from the Random Forest classifier, stepping from 64% to 77%. Significant contributions of spectral diversity indices to surveying coral health were further discussed in the light of spectral properties of coral-related pigments. These findings may play a major role for the extensive monitoring of coral health states at a fine scale, and for the management and restoration of damaged coral reefs. © 2012 by the authors.

Canavesio R.,CNRS Insular Research Center and Environment Observatory
Land Use Policy | Year: 2014

The main political concern in the southern areas of Madagascar is poverty alleviation. To alleviate poverty in the area, the government has chosen to enforce adjustment policies of the World Bank Group. According to the World Bank Group's argument, while artisanal mining is supposed to create significant economic, social and environmental problems, large-scale mining investment results in economic and social prosperity. This paper focuses principally on a re-analysis of the debates regarding the relationship between artisanal and large-scale mining and poverty alleviation in developing countries. Further, the paper offers an alternative viewpoint on these issues based on the example of Madagascar. In the last decade, Madagascar has experienced a significant increase in mining activity. Towards the end of the 90s, informal and artisanal mining emerged as one of the most important economic activities of the area with the development of the Ilakaka frontier. At the same time, foreign investments began to benefit from adjustment policies implemented by the government, and large-scale mining operations also commenced. As the local socio-economic system was deeply affected by these developments, it is wise to monitor the effects of each type of mining operation on poverty alleviation. On the one hand, it appears that governance insufficiency has hampered possibilities for broader economic prosperity through large-scale mining investments. On the other hand, while artisanal mining is frequently condemned by scholars, the negative comments seem to be overly pessimistic, as this activity can be demonstrated to provide considerable economic opportunities for both the native and migrant populations. © 2013 Elsevier Ltd.

Planes S.,CNRS Insular Research Center and Environment Observatory | Lemer S.,CNRS Insular Research Center and Environment Observatory
Molecular Ecology | Year: 2011

Studying the movement of individuals in the wild has always been a challenge in ecology. However, estimating such movement is essential in life sciences as it is the base-line for evaluating connectivity, a major component in developing management and conservation plans. Furthermore, movement, or migration, is an essential parameter in population genetics, as it directly affects genetic differentiation. The development of highly variable markers has allowed genetic discrimination between individuals within populations and at larger scales, and the availability of high-throughput technologies means that many samples and hence many individuals can be screened. These advances mean that we can now use genetic identification for tracking individuals, and hence follow both survival and reproductive output through the life cycle. The paper by Morrissey & Ferguson (2011, this issue) is a demonstration of this new capability, as authors were able to infer the movement of salmonid fish initially captured as juveniles, and later as reproductively mature adults. © 2011 Blackwell Publishing Ltd.

Mills S.C.,CNRS Insular Research Center and Environment Observatory | Cote I.M.,Simon Fraser University
Proceedings of the Royal Society B: Biological Sciences | Year: 2010

Cheating is common in cooperative interactions, but its occurrence can be controlled by various means ranging from rewarding cooperators to active punishment of cheaters. Punishment occurs in the mutualism involving the cleanerfish Labroides dimidiatus and its reef fish clients. When L. dimidiatus cheats, by taking scales and mucus rather than ectoparasites, wronged clients either chase or withhold further visits to the dishonest cleaner, which leads to more cooperative future interactions. Punishment of cheating L. dimidiatus may be effective largely because these cleaners are strictly site-attached, increasing the potential for repeated interactions between individual cleaners and clients. Here, we contrast the patterns of cheating and punishment in L. dimidiatus with its close relative, the less site-attached Labroides bicolor. Overall, L. bicolor had larger home ranges, cheated more often and, contrary to our prediction, were punished by cheated clients as frequently as, and not less often than, L. dimidiatus. However, adult L. bicolor, which had the largest home ranges, did not cheat more than younger conspecifics, suggesting that roaming, and hence the frequency of repeated interactions, has little influence on cheating and retaliation in cleaner-client relationships. We suggest that roaming cleaners offer the only option available to many site-attached reef fish seeking a cleaning service. This asymmetry in scope for partner choice encourages dishonesty by the partner with more options (i.e. L. bicolor), but to be cleaned by a cleaner that sometimes cheats may be a better option than not to be cleaned at all. © 2010 The Royal Society.

Almany G.R.,CNRS Insular Research Center and Environment Observatory
Current Biology | Year: 2015

Summary New work reveals that the large network of no-take marine reserves on the Great Barrier Reef is working splendidly. However, bold, global action is needed to eliminate threats that reserves cannot guard against. © 2015 Elsevier Ltd All rights reserved.

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