References of "Michel, Loïc"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailTowards a framework for assessment and management of cumulative human impacts on marine food webs
Giakoumi, Sylvaine; Halpern, Benjamin S.; Michel, Loïc ULg et al

in Conservation Biology (in press)

Effective ecosystem-based management requires understanding ecosystem responses to multiple human threats, rather than focusing on single threats. To understand ecosystem responses to anthropogenic ... [more ▼]

Effective ecosystem-based management requires understanding ecosystem responses to multiple human threats, rather than focusing on single threats. To understand ecosystem responses to anthropogenic threats holistically, it is necessary to know how threats affect different components within ecosystems and ultimately alter ecosystem functioning. We used a case study of a Mediterranean seagrass (Posidonia oceanica) food web and expert knowledge elicitation in an application of the initial steps of a framework for assessment of cumulative human impacts on food webs. We produced a conceptual seagrass food web model, determined the main trophic relationships, identified the main threats to the food web components, and assessed the components’ vulnerability to those threats. Some threats had high (e.g., coastal infrastructure) or low impacts (e.g., agricultural runoff) on all food web components, whereas others (e.g., introduced carnivores) had very different impacts on each component. Partitioning the ecosystem into its components enabled us to identify threats previously overlooked and to reevaluate the importance of threats commonly perceived as major. By incorporating this understanding of system vulnerability with data on changes in the state of each threat (e.g., decreasing domestic pollution and increasing fishing) into a food web model, managers may be better able to estimate and predict cumulative human impacts on ecosystems and to prioritize conservation actions. [less ▲]

Detailed reference viewed: 40 (14 ULg)
Full Text
Peer Reviewed
See detailDominant amphipods of Posidonia oceanica seagrass meadows display considerable trophic diversity
Michel, Loïc ULg; Dauby, Patrick ULg; Gobert, Sylvie ULg et al

in Marine Ecology (in press)

Gut content examination and trophic markers (fatty acids, stables isotopes of C and N) were combined to delineate the diet of the dominant species of amphipods from Mediterranean Posidonia oceanica ... [more ▼]

Gut content examination and trophic markers (fatty acids, stables isotopes of C and N) were combined to delineate the diet of the dominant species of amphipods from Mediterranean Posidonia oceanica seagrass meadows and to highlight trophic diversity among this community. Our results indicate that, although all dominant species heavily relied on macroalgal epiphytes, considerable interspecific dietary differences existed. Carbon stable isotope ratios notably showed that some of the amphipod species favored grazing on epiphytes from leaves or litter fragments (Apherusa chiereghinii, Aora spinicornis, Gammarus aequicauda), while others like Dexamine spiniventris preferred epiphytes from rhizomes. The remaining amphipods (Caprella acanthifera, Ampithoe helleri and Gammarella fucicola) readily consumed both groups. In addition, SIAR modeling suggested that most species had a mixed diet, and relied on several food items. Fatty acid analysis and gut contents revealed that contribution of microepiphytic diatoms and of benthic and suspended particulate organic matter to the diet of amphipods were anecdotal. None of the examined species seemed to graze on their seagrass host (low 18:2(n-6) and 18:3(n-3) fatty acids contents), but G. aequicauda partly relied on seagrass leaf detritus, as demonstrated by the lesser 13C-depletion of their tissues. Overall, our findings suggest that amphipods, because of their importance in transfers of organic matter from primary producers and detritus to higher rank consumers, are key-items in P. oceanica associated food webs. [less ▲]

Detailed reference viewed: 94 (31 ULg)
Full Text
See detailApplications of stable isotopes in environmental studies at the University of Liege
Sturaro, Nicolas ULg; Borges, Alberto ULg; Das, Krishna ULg et al

Poster (2015, March 26)

Measurement and use of stable isotope ratios have a long history at the University of Liege (Belgium). Since at least 30 years, applications of stable isotopes in marine ecosystems have been developed ... [more ▼]

Measurement and use of stable isotope ratios have a long history at the University of Liege (Belgium). Since at least 30 years, applications of stable isotopes in marine ecosystems have been developed within the Laboratory of Oceanology and, more recently, within the Chemical Oceanography Unit. In the Laboratory of Oceanology, one research axis is the measurement of stable isotope composition (C, N, S) in organic matter to delineate trophic web structure and to study animal diet, their trophic niches and their alteration by human activities. This methodology has been successively applied worldwide in different habitats and ecosystems (marine, freshwater, terrestrial) in temperate and tropical areas. Mediterranean food web and fish trophic ecology have received a particular attention. Coupling between trophic ecology and ecotoxicology is another area of investigation. This has been applied mainly to marine vertebrates and freshwater ecosystems. Stable isotope labelling is also used in our laboratory to study and quantify various ecological processes such as inorganic nitrogen incorporation and trophic transfers. The laboratory facilities, renewed in 2012 and managed by Dr. Gilles Lepoint, are composed of an elemental analyser (EA, vario MICRO cube, Elementar) and a gas chromatography (GC, Agilent) coupled to an isotope ratio mass spectrometer (IRMS, Isoprime 100). The GC is also equipped with a quadrupole mass spectrometer. In 2014, the Chemical Oceanography Unit, headed by Dr. Alberto Borges, has acquired and implemented an off-axis cavity ring-down spectroscopy (CRDS) for the measurements of δ15Nα, δ15Nβ, δ18O of N2O. This enables characterization of the N2O origin in a variety of aquatic environments including groundwater in Wallonia, rivers and lakes in Wallonia and Africa, coastal environments (Scheldt estuary, Lake Grevelingen, North Sea), Mediterranean seagrass beds, and Antarctic and Arctic sea-ice. [less ▲]

Detailed reference viewed: 25 (3 ULg)
Full Text
See detailUse of C, N and S stable isotope ratios to highlight resource segregation among hermit crabs from tropical seagrass meadows
Michel, Loïc ULg; Frederich, Bruno ULg; Lavitra, Thierry et al

Poster (2015, March 26)

Polyspecific seagrass meadows are ubiquitous features of tropical coastal zones. These ecosystems are of critical ecological importance, and provide a wide range of socio-economical services to local ... [more ▼]

Polyspecific seagrass meadows are ubiquitous features of tropical coastal zones. These ecosystems are of critical ecological importance, and provide a wide range of socio-economical services to local populations. Meadows however undergo multiple threats linked to human activities (increased nutrient input, overfishing, invertebrate overharvesting, etc.). It is currently hard to assess how seagrass meadows could respond to anthropogenic impacts due to poor knowledge of their functional ecology. In an effort to unravel trophic interactions ruling the food webs associated to seagrass beds of the Toliara Great Reef (SW Madagascar), we studied resource segregation between two common Diogenidae hermit crabs (Dardanus scutellatus and Ciliopagurus tricolor) using stable isotope ratios. C, N and S stable isotope ratios of bulk muscle tissue were measured via CF-EA-IRMS (Elementar Vario MicroCube EA coupled to an Isoprime 100 MS). Interspecific differences were noted in isotopic composition of carbon (δ13C = -12.22 ± 1.73 ‰ for D. scutellatus, δ13C = -14.55 ± 0.73 ‰ for C. tricolor), nitrogen (δ15N = 4.73 ± 0.53 ‰ for D. scutellatus, δ15N = 5.20 ± 0.61 ‰ for C. tricolor) and sulfur (δ34S = 14.08 ± 2.32 ‰ for D. scutellatus, δ34S = 16.73 ± 1.49 ‰ for C. tricolor), suggesting that the two species do not feed on the same items. In addition, SIBER (Stable Isotope Bayesian Ellipses in R) modeling based on C and N data clearly showed that no overlap was present in the core isotopic niches of the two species. It also indicated that the isotopic niche of D. scutellatus was greater than the one of C. tricolor, implying that the former feeds on a greater number of items than the latter. While hermit crabs are generally considered as omnivorous species, this study highlighted differences in the foraging ecology of D. scutellatus and C. tricolor. These differences could help to limit competition for food between these two species, and facilitate their coexistence in Malagasy seagrass beds. [less ▲]

Detailed reference viewed: 42 (5 ULg)
Full Text
Peer Reviewed
See detailBiodiversity and seasonal variations of zooneuston in the northwestern Mediterranean Sea
Collard, France ULg; Collignon, Amandine ULg; Hecq, Jean-Henri ULg et al

in Belgian Journal of Zoology (2015), 145(1), 40-48

Neuston includes animals and plants inhabiting the surface layer of the water column. The neustonic area is an accumulation zone for bacteria, organic molecules but also terrestrial debris. The surface ... [more ▼]

Neuston includes animals and plants inhabiting the surface layer of the water column. The neustonic area is an accumulation zone for bacteria, organic molecules but also terrestrial debris. The surface layer is also the air/water exchange region. Therefore, neustonic organisms are directly exposed to several constraints such as wind stress and turbulence. The present study aims to characterize the zooneuston in terms of abundance and biodiversity and to evaluate the impacts of wind stress on neustonic abundance. Zooneustonic and zooplanktonic (depth of 5 meters) samples were collected twice a month between 30th August 2011 and 10th July 2012 in Calvi Bay, Corsica. Zooneustonic biodiversity was high and, notably, twenty-eight copepod genera were identified. Among these copepods, several organisms, belonging to the Pontellidae family, were much more frequent in neuston than in underlying plankton and their abundance depended on wind direction. Taxon-specific trends in seasonal abundance variation were present. For example, individuals of the Acantharia Lithoptera spp. were found in summer whereas the Pontellidae Anomalocera patersoni appeared in winter. Overall, our data provide a first step towards a better knowledge of neuston community structure in the Mediterranean Sea. [less ▲]

Detailed reference viewed: 20 (3 ULg)
Full Text
See detailAre amphipods influenced by Posidonia oceanica seagrass features?
Sturaro, Nicolas ULg; Lepoint, Gilles ULg; Michel, Loïc ULg et al

Poster (2014, December 12)

In the Mediterranean Sea, the seagrass Posidonia oceanica plays an important role as habitat for invertebrates, among which amphipod crustaceans represent a dense and diverse assemblage. Recent studies ... [more ▼]

In the Mediterranean Sea, the seagrass Posidonia oceanica plays an important role as habitat for invertebrates, among which amphipod crustaceans represent a dense and diverse assemblage. Recent studies have observed that amphipod density and biomass vary significantly on small spatial scales. This patchiness may be caused by different factors, such as recruitment, competition, and predation; however, habitat features, resulting in availability of resources such as food or shelter, may also be important in structuring these assemblages. This study examined the relationships between amphipod and habitat features in a P. oceanica meadow of the Revellata Bay (Corsica). The sampling was carried out in a continuous meadow colonizing soft substrates at constant depth in August 2008. We quantified the density and biomass of each amphipod species, as well as habitat features, namely shoot density, leaf and epiphyte biomasses, percentage of leaves per shoot having alteration marks and litter biomass. Using multiple regression analyses, few weak significant relationships were identified between amphipod and habitat features. The number of species and the diversity appeared unaffected by the measured habitat features. In contrast, total amphipod density and biomass were generally positively related to the shoot density and epiphyte biomass of P. oceanica, respectively. Overall, habitat features accounted for 0-30% of the variation in the densities of the amphipod species. A distance-based linear model explained a total of 25.8% of the variation of the amphipod assemblages (of which 18.6% was explained by litter biomass). Amphipods are therefore influenced by some P. oceanica features, but only weakly. Furthermore, some features appeared to influence individual species whereas others functioned at the assemblage level. The main challenge remains in evaluating the scale at which these features act and the way in which they influence the structure of assemblages. [less ▲]

Detailed reference viewed: 17 (1 ULg)
Full Text
See detailStable isotope ratios reveal trophic niche partitioning among hermit crabs from tropical polyspecific seagrass meadows
Michel, Loïc ULg; Frederich, Bruno ULg; Lavitra, Thierry et al

Poster (2014, December 12)

Polyspecific seagrass meadows are ubiquitous features of tropical coastal zones. These ecosystems are of critical ecological importance, and provide a wide range of socio-economical services to local ... [more ▼]

Polyspecific seagrass meadows are ubiquitous features of tropical coastal zones. These ecosystems are of critical ecological importance, and provide a wide range of socio-economical services to local populations. Meadows however undergo multiple threats linked to human activities (increased nutrient input, overfishing, invertebrate overharvesting, etc.). It is currently hard to assess how seagrass meadows could respond to anthropogenic impacts due to poor knowledge of their functional ecology. In an effort to unravel trophic interactions ruling the food webs associated to seagrass beds of the Toliara Great Reef (SW Madagascar), we studied resource segregation between two common Diogenidae hermit crabs (Dardanus scutellatus and Ciliopagurus tricolor) using stable isotope ratios. Interspecific differences were noted in isotopic composition of carbon (δ13C = -12.22 ± 1.73 ‰ for D. scutellatus, δ13C = -14.55 ± 0.73 ‰ for C. tricolor), nitrogen (δ15N = 4.73 ± 0.53 ‰ for D. scutellatus, δ15N = 5.20 ± 0.61 ‰ for C. tricolor) and sulfur (δ34S = 14.08 ± 2.32 ‰ for D. scutellatus, δ34S = 16.73 ± 1.49 ‰ for C. tricolor), suggesting that the two species do not feed on the same items. In addition, SIBER (Stable Isotope Bayesian Ellipses in R) modeling based on C and N data clearly showed that no overlap was present in the core isotopic niches of the two species. It also indicated that the isotopic niche of D. scutellatus was greater than the one of C. tricolor, implying that the former feeds on a greater number of items than the latter. While hermit crabs are generally considered as omnivorous species, this study highlighted differences in the foraging ecology of D. scutellatus and C. tricolor. These differences could help to limit competition for food between these two species, and facilitate their coexistence in Malagasy seagrass beds. [less ▲]

Detailed reference viewed: 68 (15 ULg)
Full Text
See detailApplications of stable isotopes in trophic ecology and ecotoxicology
Lepoint, Gilles ULg; Remy, François ULg; Michel, Loïc ULg et al

Scientific conference (2014, September 19)

Detailed reference viewed: 33 (14 ULg)
Full Text
See detailFrom nets to bottom traps: is exploitation of Norway lobsters a suitable option for Corsican common spiny lobster fishermen?
Patrissi, Michela; Astrou, Adèle; Pelaprat, Corinne et al

Poster (2014, May 20)

In Corsica (NW Mediterranean), most of the fishing activity is composed of small-scale artisanal fisheries, and takes place on the western coast. The common spiny lobster (Palinurus elephas) is the main ... [more ▼]

In Corsica (NW Mediterranean), most of the fishing activity is composed of small-scale artisanal fisheries, and takes place on the western coast. The common spiny lobster (Palinurus elephas) is the main target of Corsican netters. However, its populations have been declining since the 1950's, questioning the sustainability of this activity. We therefore tried to assess whether the fishing effort, currently mostly focused on common spiny lobsters, could be moved towards other commercially-interesting deep crustaceans, such as the Norway lobster (Nephrops norvegicus), through diversification of artisanal fishing practices. With the help of local fishermen, we set up Scottish traps for Norway lobsters at depths of 300 to 400 meters, on sandy and muddy bottoms of both eastern and western coasts. Despite several tests using different baits and soak times at various depths or seasons, catches on the western coast were low. On the other hand, on the eastern coast, experimentation showed interesting yields, and large mean size (i.e. high commercial value) for both sexes. While more studies are needed to confirm these results and improve knowledge of Norway lobster stocks, trap fishing of this species on eastern coast of Corsica could be a suitable alternative for diversification of artisanal fisheries. [less ▲]

Detailed reference viewed: 34 (1 ULg)
Full Text
See detailLong term spatial and temporal variability in catches of common spiny lobster Palinurus elephas (Fabricius, 1787) in Corsica (NW Mediterranean): fisheries trends, biological trends or both?
Pere, Anthony; Astrou, Adèle; Patrissi, Michela et al

Conference (2014, May 20)

The small-scale fishing fleet of Corsica (France, NW Mediterranean) is mostly composed of small artisanal boats. The common spiny lobster, Palinurus elephas, is the most valuable of all caught species. As ... [more ▼]

The small-scale fishing fleet of Corsica (France, NW Mediterranean) is mostly composed of small artisanal boats. The common spiny lobster, Palinurus elephas, is the most valuable of all caught species. As a result, it is the main target of most fishermen during the 7-months fishing season. Populations of this species seem to decrease since the 1950's. The aim of this study was to understand if this decline could be linked with overfishing, or if other biological, ecological or climatic factors could explain this population drop. To achieve this goal, we combined 1) a meta-analysis of all data concerning fishing effort and captures in published and grey literature and 2) an on-board monitoring program that started in 2004. Using obtained data, we followed fleet structure, fishing effort and captures evolution from 1950 to 2011. Our results point out an important capture decrease during the 20th century. This trend started during the 1950’s and 1960’s, when trammel nets replaced traditional wood traps. A micro-regional analysis revealed that exploitation intensity widely varied among different areas around the island. Moreover, landings and catch rates showed important spatial and temporal variations. This could be caused by changes in recruitment rates. However, recruitment processes of this species are still poorly understood. Improving our knowledge of common spiny lobster life cycle will likely lead to a more comprehensive and efficient assessment of Corsican stocks of this species. [less ▲]

Detailed reference viewed: 52 (5 ULg)
Full Text
See detailStable isotopes as descriptors of trophic niches
Michel, Loïc ULg

Scientific conference (2014, March 25)

Detailed reference viewed: 31 (5 ULg)
Full Text
See detailAbstract Book of ZOOLOGY 2014, 21st Benelux Congress of Zoology
Lepoint, Gilles ULg; Michel, Loïc ULg; Schnitzler, Joseph ULg et al

Book published by Royal Belgian Zoological Society (2014)

Detailed reference viewed: 31 (4 ULg)
Full Text
Peer Reviewed
See detailBoundary lines in symbiosis forms
Parmentier, Eric ULg; Michel, Loïc ULg

in Symbiosis (2013)

Symbiosis can take different forms (parasitism, mutualism, commensalism, etc.) but boundaries between different types of symbiotic interactions are not well defined. The kinds of symbiotic associations ... [more ▼]

Symbiosis can take different forms (parasitism, mutualism, commensalism, etc.) but boundaries between different types of symbiotic interactions are not well defined. The kinds of symbiotic associations between organisms cannot however be restricted to isolated and distinct categories. These associations are part of a broad continuum in which it is difficult to know where one type of association ends and another begins. Moreover, different scientists use the same term to mean different things or different terms tomean the same thing. This can obscure what is biologically important and what is not. This communication proposes a new classification scheme, which simply and comprehensively illustrates relationships between the various kinds of associations. The scheme illustrates relationships clearly and highlights the continuum between types of associations. It further indicates where modifications to the scheme are possible over time. The classification of the association between two organisms can be reduced to two factors: 1) the impact incurred by the host (benefit or damage) and 2) the relative duration of the association (RDA), i.e. the ratio of the duration of the association to the life expectancy of the symbiont. The conceptual figure provides concrete examples and illustrates some relationships that can change during different life stages. This figure should help teachers and students in the understanding of symbiosis, and could be a starting point for future discussions in the continuously developing research fields studying ecological and evolutionary implications of symbiotic relationships. [less ▲]

Detailed reference viewed: 64 (12 ULg)
Peer Reviewed
See detailStables isotopes in the fin whale Balaenoptera physalus from the Mediterranean Sea: implications for management and conservation
Das, Krishna ULg; Lepoint, Gilles ULg; Michel, Loïc ULg et al

Poster (2013, April)

The fin whale (Balaenoptera physalus) is the commonest large whale species in the Mediterranean Sea, found mostly over deep, offshore waters of the western and central portion of the region. This whale is ... [more ▼]

The fin whale (Balaenoptera physalus) is the commonest large whale species in the Mediterranean Sea, found mostly over deep, offshore waters of the western and central portion of the region. This whale is known to feed mainly on krill in contrast to its Atlantic counterpart, displaying a more diversified diet. δ13C and δ15N values were analysed by IR-MS (Isoprime 100) coupled to an N-C-S elemental analyser (Vario MICRO Cube, Elementar) in 113 skin biopsies from Mediterranean fin whales sampled in 2010 and 2011 during WWF campaign at sea. A lipid normalization equation was applied (adapted from Post al. 2007) because the measured C:N ratio was > 3.5. Normalized δ13C and δ15N values ranged from -20.3 to -17.3 ‰ and from 5.9 to 8.9 ‰, respectively. These values are in good agreement with those collected previously on baleen plates from Mediterranean fin whales (Bentaleb et al., 2011). A mean enrichment of 3.4 ‰ was observed between δ15N values measured in fin whale skin biopsies and Mediterranean krill (Meganyctiphanes norvegica) confirming the importance of the krill as a major food source. The narrow width of the isotopic niche of the Mediterranean fin whale (evaluated by SIBER Stable Isotope Bayesian Ellipses) compared to the Atlantic fin whale (Ryan et al. 2012) raises many concerns in the context of global changes and long-term consequences. One could expect that species displaying narrow niches would be more susceptible to ecosystem fragmentation and other anthropogenic impacts. [less ▲]

Detailed reference viewed: 166 (9 ULg)
Full Text
Peer Reviewed
See detailDiet- and tissue-specific incorporation of isotopes in the shark Scyliorhinus stellaris, a North Sea mesopredator
Caut, Stephane; Jowers, Michael J.; Michel, Loïc ULg et al

in Marine Ecology. Progress Series (2013), 492

Elucidating predator–prey relationships is an important part of understanding and assessing the structure and function of ecosystems. Sharks are believed to play a significant role in marine ecosystems ... [more ▼]

Elucidating predator–prey relationships is an important part of understanding and assessing the structure and function of ecosystems. Sharks are believed to play a significant role in marine ecosystems, although their specific trophic ecology is largely unexplored. Stable isotopes of nitrogen ( 15N) and carbon ( 1318 C) are a widely applied tool in food web studies but there is a need to quantify stable isotope dynamics in animals, particularly sharks. In this study, diet-tissue discrimination factors (DTDF = stable isotope in consumer tissue – stable isotope in diet) and turnover rates (time for the isotope to be assimilated into the consumer’s tissue) of stable isotopes were estimated in blood, fin, and muscle tissue for the shark species Scyliorhinus stellaris fed two diets with different isotope values. Subsequently, these diet- and tissue-specific DTDFs were used in isotopic mixing models to quantify the diet of Scyliorhinus canicula caught in the North Sea and compared with stomach content data. DTDFs for 15N ( 15N) and 13C ( 13C) ranged from –1.95‰ to 3.49‰ and from 0.52‰ to 5.14‰, respectively, and varied with tissue and diet type. Isotope turnover rates in plasma and red blood cells, expressed as half-lives, range from 39 to 135 days. A majority of the variability of DTDFs reported in this and other studies with sharks can be explained by linear relationships between DTDF and dietary isotopic values. From these relationships, we propose a method for isotope mixing models that uses diet specific DTDFs, which improves diet reconstruction estimates of animals, particularly mesopredator sharks that consume a large range of prey types. [less ▲]

Detailed reference viewed: 73 (20 ULg)
Full Text
Peer Reviewed
See detailDiet of harbor porpoises along the Dutch coast: a combined stable isotope and stomach contents approach
Jansen, Okka; Michel, Loïc ULg; Lepoint, Gilles ULg et al

in Marine Mammal Science (2013), 29(3), 295-311

High stranding frequency of porpoises, Phocoena phocoena, along the Dutch coast since 2006 has led to increased interest in the ecology of porpoises in the North Sea. Stranded porpoises were collected ... [more ▼]

High stranding frequency of porpoises, Phocoena phocoena, along the Dutch coast since 2006 has led to increased interest in the ecology of porpoises in the North Sea. Stranded porpoises were collected along the Dutch coast (2006–2008) and their diet was assessed through stomach content and stable isotope analysis (d13C and d15N) of porpoise muscle and prey. Stable isotope analysis (SIAR) was used to estimate the con- tribution of prey species to the porpoises’ diet. This was compared to prey composi- tion from stomach contents, to analyze differences between long- and short-term diet. According to stomach contents, 90.5% of the diet consisted of gobies, whiting, lesser sandeel, herring, cod, and sprat. Stable isotope analysis revealed that 70-83% of the diet consisted of poor cod, mackerel, greater sandeel, lesser sandeel, sprat, and gobies, highlighting a higher importance of pelagic, schooling species in the porpoises’ diet compared to stomach contents. This could be due to prey distribution as well as differ- ences in behavior of porpoises and prey between the coastal zone and offshore waters. This study supports the need for multi-method approaches. Future ecological and fishery impact assessment studies and management decisions for porpoise conservation should acknowledge this difference between the long- and short-term diet. [less ▲]

Detailed reference viewed: 103 (22 ULg)
Full Text
See detailTrophic tracers reveal considerable diversity among diets of dominant amphipods from Posidonia oceanica seagrass meadows
Michel, Loïc ULg; Dauby, Patrick ULg; Gobert, Sylvie ULg et al

Poster (2012, August 20)

Mediterranean Posidonia oceanica meadows shelter a high biomass and an important biodiversity of amphipod crustaceans. In other temperate meadows, the amphipods play an important part in the functioning ... [more ▼]

Mediterranean Posidonia oceanica meadows shelter a high biomass and an important biodiversity of amphipod crustaceans. In other temperate meadows, the amphipods play an important part in the functioning of the ecosystem, notably in organic matter transfers from producers to higher level consumers. However, the situation in Posidonia oceanica meadows remains unclear, and little is known about the trophic ecology of amphipods, which are generally regarded as generalist herbivores/detritivores despite the lack of precise studies. Here, we combined gut content examination and trophic markers (fatty acids, stables isotopes of C and N) to delineate the diet of the dominant species of amphipods from Posidonia oceanica seagrass meadows and to highlight trophic diversity among this community. Our results indicate that contribution of microepiphytic diatoms and of benthic and suspended particulate organic matter to the diet of amphipods were anecdotal. On the other hand, all dominant species heavily relied on macroalgal epiphytes, suggesting a certain extent of overlapping in the diets of the dominant species. Considerable interspecific differences nonetheless existed, notably concerning grazing preferences towards epiphytes from leaves or litter fragments vs. epiphytes from rhizomes. In addition, the use of the SIAR isotopic mixing model showed that most species had a mixed diet, and relied on several food items. None of the examined species seemed to graze on their seagrass host, but Gammarus aequicauda partly relied on seagrass leaf detritus. Overall, our findings demonstrate that amphipods have the potential to be key-items in trophic and functional interactions occurring among Mediterranean Posidonia oceanica meadows. [less ▲]

Detailed reference viewed: 57 (10 ULg)
Full Text
See detailStare-Capmed : Présentation générale du projet et exemple d'une action : "Impact de l'ancrage sur la dynamique des herbiers de posidonies".
Michel, Loïc ULg; Champenois, Willy ULg; Borges, Alberto ULg et al

Conference (2012, May 16)

STARE-CAPMED (STAtion of Reference and rEsearch on Change of local and global Anthropogenic Pressures on Mediterranean Ecosystems Drifts) est un projet de recherche mis en place par Stareso S.A.S. depuis ... [more ▼]

STARE-CAPMED (STAtion of Reference and rEsearch on Change of local and global Anthropogenic Pressures on Mediterranean Ecosystems Drifts) est un projet de recherche mis en place par Stareso S.A.S. depuis janvier 2012. Il a pour objectif d’établir un site de référence à long terme pour la compréhension, par la recherche fondamentale, des processus de l’évolution des écosystèmes méditerranéens côtiers et océaniques en réponse aux changements actuels globaux et locaux des pressions anthropiques. Centré sur la Baie de Calvi et le proche large, il vise à fournir un référentiel basé sur des mesures à haute fréquence qui doivent pouvoir complémenter les réseaux de surveillance basse fréquence et de recherches existants et ainsi faire progresser la compréhension des processus. En outre, le projet doit fournir aux utilisateurs finaux (collectivités locales et régionales, administrations nationales, ...) des orientations de gestion basées sur l’analyse étayée des processus en jeux. Financé par l’Agence de l’eau RMC et la Collectivité Territoriale de Corse, le projet, multidisciplinaire, se décline actuellement selon 10 axes de travail : • Suivi du cadre hydrographique et physico-chimique • Suivi et quantification des pressions anthropiques • Ecosystème planctonique • Benthos de substrat meuble • Benthos de substrat dur et faune vagile • Phanérogames marines et écosystèmes associés • Mouillages et processus d’altération des herbiers de posidonies • Ecotoxicologie et polluants émergents • Bilan CO2 et métabolisme des écosystèmes • Zones protégées, espèces nouvelles, recrutement Pour chacun de ces axes, la stratégie d’échantillonnage est basée sur la comparaison de données obtenues durant des périodes où l’impact anthropique est faible (octobre-avril) avec celles obtenues durant des périodes de pression intense (mai-septembre), et sur la comparaison de données issues de sites de référence peu impactés avec celles provenant de sites où l’impact anthropique est reconnu. A titre d’exemple, le but de l’action "Mouillages et processus d’altération des herbiers de posidonies" est de mettre en évidence les conséquences des altérations liées à l’arrachage de faisceaux de posidonies sur la vitalité de l’herbier. Des zones où la pression de mouillage est reconnue seront définies sur base des travaux de cartographie de l’herbier, également réalisés dans le cadre du projet STARE-CAPMED. Elles seront comparées avec des zones d’herbiers sains témoins par la caractérisation du sédiment (mesures de compacité in situ, mesures des concentrations en O2 et nutriments et du pH de l’eau interstitielle, granulométrie et teneur en matière organique du sédiment, proportions de rhizomes et morts) ainsi que par la définition de l’état physiologique des faisceaux de posidonies (mesures biométriques classiques, analyses des contenus élémentaires en carbone, azote et phosphore) et par l’application d’indices écologiques définis par la DCE (PREI, BIPO, …). Les résultats obtenus permettront d’avoir une vue d’ensemble des processus par lesquels l’impact physique des mouillages de bateaux de plaisance occasionne des dégâts aux herbiers de posidonies. Ils pourront ainsi fournir une base de connaissances solide aux gestionnaires soucieux de limiter cet impact. [less ▲]

Detailed reference viewed: 261 (34 ULg)
Full Text
Peer Reviewed
See detailFeeding ecology of harbour porpoises: stable isotope analysis of carbon and nitrogen in muscle and bone
Jansen, Okka; Geert, Aarts; Das, Krishna ULg et al

in Marine Biology Research (2012), 8(9), 829-841

Harbour porpoises are the most common small cetaceans in the North Sea and Dutch coastal waters. To study their trophic level and feeding location, stable carbon and nitrogen isotope ratios (d13C and d15N ... [more ▼]

Harbour porpoises are the most common small cetaceans in the North Sea and Dutch coastal waters. To study their trophic level and feeding location, stable carbon and nitrogen isotope ratios (d13C and d15N) were analysed in muscle and bone samples collected from 157 porpoises stranded along the Dutch coast (2006􏰄2008). In addition, samples from 30 prey species were analysed. Prey samples showed high d15N values in species of higher trophic level. In addition, geographic differences in isotopic composition were found, with higher d15N and d13C values in prey from more southern, coastal and estuarine areas. Based on muscle d15N values, we found neonatal enrichment and that larger porpoises, in particular males, seem to feed on lower trophic level species, compared to smaller individuals. Also bone d15N values show that larger animals had fed on lower trophic levels in distant times. Porpoises from the Eastern Scheldt reveal distinct d13C values in muscle, but not in bone. This shows that these animals had foraged in the Eastern Scheldt for a longer time period but were not born there. Seasonal variation in bone d15N and d13C values revealed two distinct groups of porpoises along the Dutch coast, a winter group (mainly males) that migrated from neighbouring regions and a Dutch subpopulation in summer. These results furthered our insight about shifts in trophic level and feeding location of harbour porpoises from the southern North Sea over time. [less ▲]

Detailed reference viewed: 81 (9 ULg)