Metabarcoding as a tool to enhance marine surveillance of nonindigenous species in tropical harbors: A case study in Tahiti

Globalization has increased connectivity between countries enhancing the spread of marine nonindigenous species (NIS). The establishment of marine NIS shows substantial negative effects on the structure and functioning of the natural ecosystems by competing for habitats and resources. Ports are often hubs for the spread of NIS via commercial and recreational vessels. Prevention, detection, and mitigation efforts are required to avoid and manage the establishment of NIS in new ecosystems. In this study, metabarcoding approaches targeting the nuclear small-subunit ribosomal RNA (18S rRNA) gene and mitochondrial cytochrome c oxidase I (COI) gene were used to investigate planktonic and sessile (i.e., biofouling) communities and NIS at four locations in Tahiti, including two marinas and one port with varying anthropogenic impacts, and a relatively pristine site (Manava) used as a control. ASV richness values showed significant differences (18S rRNA gene: p = .023; COI: p < .001) between locations in the plankton samples, with the control site (low impact) having the highest diversity for both genes. ASV richness was also significantly different among locations for the biofouling samples in the COI dataset (p = .002). Community composition differed between locations with spatial patterns appearing stronger for the plankton samples compared with the biofouling samples. Detection of NIS based on selected lists of globally invasive species revealed a wide diversity of potentially invasive taxa especially in the more anthropogenically impacted regions. The use of a multigene approach improved the detection of NIS. This study demonstrates the utility of using a metabarcoding approach to routinely monitor areas most at risk from NIS establishment in Tahiti and other coastal nations. These coastal nations are vulnerable to shipping-mediated incursions, and baseline information is required for both native diversity and nonindigenous diversity.publishedVersio

Diversity, systematics and biogeography of French Polynesian Lobophora (Dictyotales, Phaeophyceae)

We re-evaluated the diversity of Lobophora using an integrative taxonomic approach based on a broad sampling across French Polynesian archipelagos. Our results show that French Polynesia supports at least 37 Lobophora species of which ~57% (21) are endemic. This level of endemicity is comparable to that presently known in the Caribbean and the western Indian Ocean, while French Polynesian coastlines cover a much smaller length. With a third of the species in common, French Polynesia shares considerable biogeographic affinities with the Melanesian Islands, situated over 4000 km to the west. Distribution ranges of a few species reach the western Indian Ocean, and two species also occur in the Atlantic. We hypothesize that Lobophora species in French Polynesia have mainly evolved into endemic species from colonizers originating from the Central Indo-Pacific. These rare dispersal events to ocean archipelagos followed by a long period of isolation and speciation represent an important process responsible for the high level of endemism in remote archipelagos. While south-eastern Pacific Islands could be considered an ‘evolutionary graveyard’ for the genus Lobophora as little local radiation occurred, this may simply be due to recent evolutionary history. Based on these new data, the diversity of Lobophora represents ~10% of French Polynesian seaweed diversity. Eighteen new species of Lobophora are here described from French Polynesia

Macroalgal diversity for sustainable biotechnological development in French tropical overseas territories

This review focuses on the diversity of French tropical overseas macroalgae and their biotechnological applications. After listing the specific diversity, i.e. 641 species in French Antilles in the Atlantic Ocean, 560 species in the Indian Ocean, and 1015 species in the South Pacific Ocean, we present the potential of their metabolites and their main uses. Among the great diversity of metabolites, we focus on carbohydrates, proteins, lipids, pigments and secondary metabolites, in particular terpenes and phenolic compounds. The main applications of reef macroalgae are described in human and animal consumptions, phycocolloids extraction, production of active ingredients for health, cosmetics, agriculture, and bioremediation. For each application, we list what has been done, or will be done in French tropical overseas territories and point out the challenges faced when using this chemo-diversity, and problems linked to their exploitation. Finally, we discuss challenges to develop seaweed farming, their uses in carbon sequestration and resilience to global change, their uses for alternative proteins together with the production of bioenergy and biomaterials. As a conclusion, we encourage the research on the chemo-diversity of French reef macroalgae for industrial applications as these organisms represent a reservoir of active ingredients that is still insufficiently explored

Diversité et valorisation des algues brunes proliférantes de la famille des Dictyotaceae des lagons de Tahiti

International audienc

Photosynthesis, pigment composition and antioxidant defences in the red alga Gracilariopsis tenuifrons (Gracilariales, Rhodophyta) under environmental stress

International audienc

Les crustacés de l'île de Juan de Nova (Crustacea Decapoda Stomatopoda) mission BIORECIE 3-19 décembre 2013

Les crustacés décapodes et stomatopodes sont inventoriés pour la première fois de l’île de Juan de Nova. Au total 111 espèces sont reconnues, 69 crabes, 28 anomoures, 10 crevettes, 3 stomatopodes et 1 langouste. Cette liste est disponible sur Internet, avec des photographies, dans la base IRENav/CRUSTA (http://crustiesfroverseas.free.fr/search_result.php?refregion=Juan de Nova). Le bilan de cet inventaire est plus modeste que ceux effectués précédemment pendant les campagnes BIORECIE, à Europa en 2011 (175 espèces) et aux Glorieuses en 2012 (157 espèces). Plus qu’à une plus faible biodiversité, ce résultat est attribué aux difficultés d’échantillonnage à Juan de Nova, avec un platier difficile d’accès, très étendu (2-3 km) et découvrant par ailleurs peu aux moments des basses mer de cette campagne. La faune terrestre est un peu plus riche qu’à Europa, avec la présence du crabe de cocotier Birgus latro et du crabe Geograpsus grayi, mais un peu plus pauvre qu’aux Glorieuses qui compte deux espèces supplémentaires (Coenobita brevimanus et Discoplax rotunda). Une tentative de distribution des espèces par habitats est proposée en adoptant une cartographie simplifiée : milieu terrestre, supra et intertidal, platier sableux, platier corallien, front récifal et récif externe. Les inventaires pour les îles Eparses sont également comparés à celui réalisé pour les Comores, essentiellement Mayotte (483 espèces), zone mieux échantillonnée et beaucoup plus riche car disposant de biotopes plus étendus et plus variés. La faune des îles Eparses est typiquement indo-ouest pacifique dans sa composition avec cependant un petit groupe d’espèces qui ne sont connues que de l’ouest de l’océan Indien. Trois espèces ne sont toujours connues que de îles Eparses : Pagurixus annulus et P. europa Komai & Poupin (2013) et Thalamita pseudospinifera Crosnier (1975) Une forme a été identifiée comme cryptique, correspondant vraisemblablement à une nouvelle espèce (Calcinus aff. pulcher)

Insights into the Metabolome of the Cyanobacterium Leibleinia gracilis from the Lagoon of Tahiti and First Inspection of Its Variability

Cyanobacteria are known to produce a large diversity of specialized metabolites that can cause severe (eco)toxicological effects. In the lagoon of Tahiti, the benthic cyanobacterium Leibleinia gracilis is commonly found overgrowing the proliferative macroalga Turbinaria ornata or dead branching corals. The specialized metabolome of the cyanobacterium L. gracilis was therefore investigated together with its variability on both substrates and changes in environmental parameters. For the study of the metabolome variability, replicates of L. gracilis were collected in the same location of the lagoon of Tahiti before and after a raining event, both on dead corals and on T. ornata. The variability in the metabolome was inferred from a comparative non-targeted metabolomic using high resolution mass spectrometry (MS) data and a molecular network analysis built through MS/MS analyses. Oxidized fatty acid derivatives including the unusual 11-oxopalmitelaidic acid were found as major constituents of the specialized metabolome of this species. Significant variations in the metabolome of the cyanobacteria were observed, being more important with a change in environmental factors. Erucamide was found to be the main chemical marker highly present when the cyanobacterium grows on the macroalga. This study highlights the importance of combined approaches in metabolomics and molecular networks to inspect the variability in the metabolome of cyanobacteria with applications for ecological questions

Illustrated Checklist of the Decapoda at Europa Island

International audienc

Crustacea Decapoda of Glorieuses Islands, with notes on the distribution of the coconut crab (Birgus latro) in the Western Indian Ocean

International audienc

Chemogeography of the red macroalgae asparagopsis: metabolomics, bioactivity, and relation to invasiveness

Introduction The Latitudinal Gradient Hypothesis (LGH) foresees that specialized metabolites are overexpressed under low latitudes, where organisms are subjected to higher herbivory pressure. The widespread macroalga Asparagopsis taxiformis is composed of six distinct genetic lineages, some of them being introduced in many regions. Objectives To study (i) metabolic fingerprints of the macroalga and (ii) its bioactivity in space and time, both as proxies of its investment in defensive traits, in order to assess links between bioactivities and metabotypes with macroalgal invasiveness. Methods 289 macroalgal individuals, from four tropical and three temperate regions, were analyzed using untargeted metabolomics and the standardized Microtox (R) assay. Results Metabotypes showed a low divergence between tropical and temperate populations, while bioactivities were higher in temperate populations. However, these phenotypes varied significantly in time, with a higher variability in tropical regions. Bioactivities were high and stable in temperate regions, whereas they were low and much variable in tropical regions. Although the introduced lineage two exhibited the highest bioactivities, this lineage could also present variable proliferation fates. Conclusion The metabolomic approach partly discriminates macroalgal populations from various geographic origins. The production of chemical defenses assessed by the bioactivity assay does not match the macroalgal genetic lineage and seems more driven by the environment. The higher content of chemical defenses in temperate versus tropical populations is not in accordance with the LGH and cannot be related to the invasiveness of the macroalgae