The nutritional quality of non-calcified macroalgae in Guadeloupe (Lesser Antilles) evaluated by their biochemical composition

Biochemical compositions of 15 species and 1 genus of macroalgae were studied. Concentrations of macronutrients were measured to evaluate their nutritional quality. High concentrations of proteins, lipids and soluble carbohydrates generally indicate a high nutritional quality because these compounds are readily metabolically available for consumers and provide a large proportion of energy. Insoluble carbohydrates are more difficult to digest and high concentrations indicate a low nutritional quality. Three groups of macroalgae were identified according to their biochemical characteristics. The first group clusters Ceramium cf nitens, Ulva cf lactuca and Lobophora cf variegata due to their high concentrations of proteins and soluble carbohydrates, and low proportion of ashes. These species presented high nutritional qualities and, according to previous studies, are preferredby herbivorous fishes. A second group constituted by Dictyota cf pulchella, Caulerpa cupressoides, C. sertularioides and Sargassum cf polyceratium presented intermediate nutritional qualities due to higher concentrations of lipids and insoluble carbohydrates. Finally, the others species and genus are characterized by a high proportion of ashes and a low nutritional quality. However, some of these species (Acanthophora spicifera, Padina cf sanctae-crucis or Laurencia cf chondrioides) are cited as preferred macroalgae for some herbivorous fishes. The present study indicates that the biochemical composition in macronutrients only partially explains the food choice made by fishes. The consumption of macroalgae by herbivores depends also on the presence of deterrent molecules, the composition in micronutrients, and their palatability that often decreased with increasing size. Most of macroalgae are preferentially consumed when young and small

Host use of the elkhorn coral crab <i>Domecia acanthophora</i> (Brachyura : Domeciidae), with a phylogeny of the genus

Coral-dwelling crabs form a diverse community on coral reefs, and various families independently colonised scleractinian corals. Species of Domecia have a circumtropical distribution, with two known species in the Indo-Pacific, one in the West Atlantic and one in the East Atlantic. New host records for the West Atlantic species D. acanthophora are recorded from Guadeloupe, as well as the first dwellings in Acropora prolifera from Curaçao. Here we provide an overview of all known hosts of Domecia species and, based on COI mtDNA, the first phylogeny of the genus. The coral Orbicella faveolata and the sponge Callyspongia sp. are recorded as new hosts for D. acanthophora. Host records for this species now include eight scleractinian hosts, Millepora fire corals and records on sponges. Our phylogenetic reconstruction shows that D. acanthophora is closest to the wide-ranging Indo-Pacific species D. hispida, and more distantly related to D. glabra. Domecia acanthophora appears to be less host specific than its congeners D. hispida and D. glabra that predominantly associate with Pocillopora and Acropora corals, respectively. Differences in host-specificity between Indo-Pacific and Atlantic species are briefly discussed in the light of similar observations on other coral-dwelling crab species

Detection of Adsorbed Chlordecone on Microplastics in Marine Sediments in Guadeloupe: A Preliminary Study

Plastic pollution in the oceans is recognized as a worldwide problem. Since the 1950s, the production of plastics has been increasing and the first reports of microplastics (particles \u3c 500 μm) in the marine environment began to appear in the 1970s. These particles represent a growing environmental problem due to their dispersion in seawater and marine organisms. Additionally, microparticles in general can adsorb pollutants that will then become bioavailable to organisms by being desorbed during digestion, which could be an important pathway for the contamination of organisms. In Guadeloupe and Martinique, an organochlorine pesticide called “chlordecone” was used from 1972 to 1993 in banana plantations and this very persistent pollutant contaminates soils, rivers, and coastal marine areas and accumulates in marine foodwebs. To examine these issues, we had two goals: 1) to assess the contamination of marine sediments by microplastics surrounding Guadeloupe; and 2) to determine the ability of microplastics to adsorb chlordecone, as has been demonstrated for other organochlorine pollutants. To do so, marine sediments were collected in triplicate from 12 sites in coral reef environments around the island. Microplastics from each sample were then enumerated by size, color and shape under a binocular microscope. The results indicate that microplastics are found in all the studied sites and that their distribution could be linked to marine currents or proximity to areas of significant human activities (port activities, agglomeration, etc.). Finally, our preliminary results indicated that chlordecone could be adsorbed onto microplastics, with a concentration ranging from 0.00036—0.00173 µg/µg of microfilter

Bilan des connaissances sur la contamination de la faune marine par la chlordécone en Guadeloupe et en Martinique

Le projet Chlohal, intitulé « Consolidation des connaissances sur la contamination de la faune halieutique par la chlordécone » a été mis en place grâce à une collaboration entre l\u27IFREMER et l\u27Université des Antilles et de la Guyane. Le premier objectif de ce projet est de compléter les connaissances actuelles sur le niveau de contamination des espèces et leur distribution géographique. Le second objectif a pour but de comprendre le mode de transfert de la molécule au sein des milieux marins (mangrove, herbiers, récifs coralliens) en analysant la contamination des différents compartiments trophiques, des producteurs primaires aux prédateurs

Trophic niches of the herbivourous fishes of the Caribbean : contributions of stable isotopes

Les poissons herbivores jouent un rôle écologique majeur face au phénomène de « coral-algal phase-shift », qui sévit depuis le début des années 80 dans les récifs coralliens de la Caraïbe. Dans cette étude, les habitudes alimentaires des principales espèces de poissons herbivores ont été étudiées afin de comprendre comment ces espèces utilisent et se partagent les ressources trophiques en milieu récifal et dans les herbiers. Les niches trophiques de ces espèces ont été décrites par deux méthodes complémentaires: les analyses des contenus des tractus digestifs et les analyses des isotopes stables du carbone C3C/ 12C) et de l'azoteCSN/ '4N). La qualité nutritionnelle des sources alimentaires a été évaluée par leurs concentrations de macronutriments (protéines, lipides, glucides solubles et insolubles) afin d'expliquer en partie le choix des ressources par les herbivores. Parmi les 14 espèces de poissons étudiées, appartenant aux familles des Pomacentridae, des Acanthuridae et des Scaridae, huit types de niches trophiques ont été décrits, indiquant une diversité fonctionnelle de ces espèces. Les niches trophiques décrites sont occupées par une ou plusieurs espèces, indépendamment de leur morphologie et de leurs affinités taxinomiques. Les résultats de cette étude suggèrent une complémentarité entre ces espèces, en terme d'utilisation des ressources, et soulèvent la question de leur conservation afin de préserver leur rôle écologique dans les écosystèmes côtiers de la Caraïbe.Herbivorous fishes play a major ecological role against the « coral-algal phase-shift » phenomenon in the coral reefs of the Caribbean. In this study, the feeding patterns of the most important species of herbivorous fishes have been studied to understand how these species use and share the trophic resources on reefs and seagrass beds . Trophic niches of these species have been described by two complementary methods: the analyses oftheir digestive contents and the analyses of stable isotopes of carbon C3C/ J2C) and nitrogen (lsN/14N). The nutritional quality of the sources has been evaluated by their concentrations of macronutrients (proteins, lipids, soluble and insoluble carbohydrates) to explain partially the choice of resources by herbivorous fishes . Among the 14 studied species of herbivorous fishes (Pomacentridae, Acanthuridae and Scaridae), eight types of trophic niches have been described, indicating a functional diversity of these species . The trophic niches are occupied by one or several species, independently oftheir morphology or their taxonomie affinities. The results of this study suggest a complementarity among these species and raise the question of their conservation to preserve their ecological role on marine ecosystems of the Caribbean

Biosorption capacity of genus Dictyota facing organochlorine pesticide pollutions in coastal areas of the Lesser Antilles

International audienceMeasurements of chlordecone, an organochlorine insecticide with high persistence in natural environments, have been carried out on several species and genus of macroalgae in Guadeloupe and Martinique. These data were statistically compared to determine the ability of the genus Dictyota to accumulate chlordecone, compared to other collected macroalgae. The comparisons were conducted between phylogenetic groups (Rhodophyta, Phaeophyta and Chlorophyta), and between sites (Guadeloupe vs Martinique). Concentrations of chlordecone measured in Dictyota spp. samples were significantly higher than the other groups regardless to the site. Phaeophytes are generally characterized by a higher capacity for biosorption of contaminants. In this study, however, only the Dictyota spp. samples followed this pattern. Therefore, this genus is of interest in cases of phycoremediation of the chlordecone

The invasive lionfish, Pterois volitans, used as a sentinel species to assess the organochlorine pollution by chlordecone in Guadeloupe (Lesser Antilles)

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Partitioning of food resources among three sympatric scorpionfish (Scorpaeniformes) in coastal waters of the northern Yellow Sea

International audienceThe partitioning of food resources among three abundant co-occurring reef-associated scorpionfish, Hexagrammos agrammus, Hexagrammos otakii and Sebastes schlegelii, was determined on an artificial reef zone in nearshore and offshore coastal waters of northern China, using stomach content and stable isotope analyses (δ13C and δ15N). The three species consumed similar prey items, mainly a variety of crustaceans, teleosts, polychaetes and macroalgae, but the proportions of the items differed among species. The dietary composition of all three scorpionfish differed significantly in nearshore waters, but not between H. otakii and S. schlegelii in offshore waters, where both species fed predominantly on carideans, penaeids and brachyurans. The δ13C values varied significantly among the three scorpionfish in nearshore waters, and tended towards significance (P = 0.053) between H. otakii and S. schlegelii in offshore waters, suggesting that they partition food resources. Bayesian mixing models further confirmed that all scorpionfish were generalist carnivorous and that the main food sources were assimilated in different proportions. In the nearshore waters, resource partitioning occurs among the three scorpionfish, reducing the potential for competition and the feeding ecology implies that they have dietary plasticity, which facilitates their coexistence and maintains local benthic fish community stability

Diversity of trophic niches among herbivorous fishes on a Caribbean reef (Guadeloupe, Lesser Antilles), evidenced by stable isotope and gut content analyses

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