References of "Lepoint, Gilles"
     in
Bookmark and Share    
See detailStable isotope ratios suggest limited trophic importance of seagrasses for invertebrate consumers from Malagasy tropical polyspecific seagrass meadows
Michel, Loïc ULg; Wang, Haolin; Frederich, Bruno ULg et al

Conference (2015, October 09)

Polyspecific seagrass meadows are of critical ecological importance in tropical coastal zones. These ecosystems provide a wide range of socio-economical services to local populations. Meadows however ... [more ▼]

Polyspecific seagrass meadows are of critical ecological importance in tropical coastal zones. These ecosystems 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 difficult to assess how seagrass meadows could respond to anthropogenic impacts due to poor knowledge of their functional ecology. Here, stable isotope ratios of carbon, nitrogen and sulfur were used to unravel trophic interactions ruling the food webs associated to seagrass beds of the Toliara Great Reef (SW Madagascar). The contributions of various potential food items (sediment-associated and suspended particulate organic matter, plankton, leaves, roots and epiphytes of 7 seagrasses and thalli of 7 dominant macroalgae) to the diet of 20 invertebrate taxa (one sea urchin, 2 sea stars, 2 sea cucumbers, 5 gastropods including one sea hare, one bivalve, 2 amphipods, one leptostracan, one cumacean 2 hermit crabs and 3 shrimps) were assessed using a Bayesian stable isotope mixing model. Model outputs revealed that important trophic diversity existed among the invertebrate assemblage. In some groups (e.g. hermit crabs and amphipods), resource use by morphologically and taxonomically close taxa was markedly different. Many of the dominant taxa heavily relied on macroalgae for their nutrition. On the other hand, few species apparently consumed seagrass tissues. Moreover, when they did, seagrass generally accounted for a minor portion of the diet only. Overall, our results suggest that seagrass grazing in meadows of the Toliara Great Reef could be lower than in other tropical areas. These discrepancies could be linked with seasonal variation in resource availability or with eutrophication. Higher nutrient load is indeed known to cause ecosystem phase shifts and it may induce diet shift to algivory in some invertebrate consumers. [less ▲]

Detailed reference viewed: 43 (5 ULg)
Full Text
See detailApplying Stable Isotopes Bayesian Ellipses (SIBER) to characterise trophic niches of large cetaceans from the north-Western Medterranean Sea
Pinzone, Marianna ULg; Michel, Loïc ULg; Ody, Denis et al

Poster (2015, October 08)

Diet composition and feeding preferences are of critical importance to understand a species' ecology; better knowledge of these matters is necessary for efficient conservation. Few is known on the trophic ... [more ▼]

Diet composition and feeding preferences are of critical importance to understand a species' ecology; better knowledge of these matters is necessary for efficient conservation. Few is known on the trophic ecology of Mediterranean cetacean populations and the elusiveness of these organisms limits acquisition of new information. Here, we analysed C and N isotopic ratios of skin biopsies of 17 fin whales Balaenoptera physalus, 15 long-finned pilot whales Globicephala melas and 25 sperm whales Physeter macrocephalus sampled through darting between summer 2010 and 2013 in the North-Western Mediterranean Sea. We subsequently used the SIBER R package to explore isotopic niche parameters as a proxy for trophic niches assessment. Fitting of standard ellipses to each species revealed that no niche overlap between the odontocetes and fin whales was present, in accordance with the lower trophic level of the latter. Moreover, overlap between the isotopic niches of the two odontocetes was limited, confirming resource partitioning between these two species. This could be linked with differences in hunting periods and depths and consequently in prey availability. Bayesian modelling of standard ellipses revealed that the isotopic niche of fin whales was larger than the two odontocetes in over 99.80% of 106 model simulations. It is the first time that such variability is observed in Mediterranean fin whales. This suggests possible exploitation of food items from different trophic levels (krill, small fishes) or from other regions, such as other areas in the Mediterranean Sea and the North-East Atlantic. Modelling also suggested that no meaningful differences were present in the width of isotopic niches of the two odontocetes. The very narrow isotopic niche of pilot whales is in strong contrast with the generalist feeding behaviour this species is believed to have according to literature analysis. Our results open new perspectives on the ecological role of Mediterranean cetaceans. [less ▲]

Detailed reference viewed: 15 (4 ULg)
Full Text
Peer Reviewed
See detailDGTs, a complementary tool towards more efficient biomonitoring practices
Richir, Jonathan ULg; Lepoint, Gilles ULg; Donnay, Annick et al

Conference (2015, October 01)

Among the diversity of contaminants, trace elements (TEs) remain of concern because of their persistence, their ability to accumulate in biota and their toxicity. The direct measurement of their dissolved ... [more ▼]

Among the diversity of contaminants, trace elements (TEs) remain of concern because of their persistence, their ability to accumulate in biota and their toxicity. The direct measurement of their dissolved concentrations only gives punctual and fluctuating information, and often remains below detection limits of analytical methods. The more appropriate use of sentinel organisms, or bioindicators, to monitor TEs has thus often been preferred in environmental surveys. The introduction of the diffusive gradients in thin films (DGTs) technique has however participated to progressively change this binary view - bioindicator vs water - of the coastal monitoring of TEs, and DGTs rapidly became a relevant complementary tool to bioindicators, has illustrated below. In the framework of the STARECAPMED project, the ecology and the ecotoxicology of TEs were studied in the seagrass Posidonia oceanica (L.) Delile and the mussel Mytilus galloprovincialis Lamarck, 1819. DGTs (free- and pore-water probes) were deployed before sampling of organisms. TEs were also analyzed in suspended matter (dissolved and suspended-particulate TE speciation). Studies were performed in the Calvi Bay (Corsica, France), northwestern Mediterranean. TE concentrations in organisms and suspended matter or in DGT resins were measured by DRC-ICP-MS after HNO3/H202 mineralization or after a 24h elution in HNO3 1M, respectively. (1) TE bioaccumulation was first seasonally studied in P. oceanica over 3 years. Dissolved TE concentrations monitored with DGTs were low to very low. TE bioaccumulation dynamics in P. oceanica could thus be linked to the natural physiological cycle of the plant, in clean environmental conditions. (2) To complement that field survey, isolated seagrasses were in situ contaminated with TEs at environmental relevant concentrations. Through the use of DGTs, TE uptake kinetics were modelled for seagrasses exposed to know bioavailable concentrations of contaminants, as were loss kinetics during the following depuration phase. The TE sequestration ability of a healthy P. oceanica meadow facing sudden trace metal contamination events could also be quantified. (3) The deployment of pore-water DGT probes in bare-sand or seagrass colonized sediments further showed that, through its stabilizing function of the seabed, P. oceanica maintained higher TE levels in the pore-water. P. oceanica meadows thus offer a significant “depuration-filtering” ecological service along highly anthropized Mediterranean coasts. M. galloprovincialis are widely used in large spatial scale coastal monitoring surveys. (4) The deployment of caged mussels together with DGTs showed that the little contaminated water body of the Calvi Bay was relatively homogenous. It also allowed to calculate TE bioaccumulation towards mussels in reference conditions, and to compare it to native mussel populations. (5) Finally, during a 5 months mussel caging survey, mussels and suspended matter were collected weekly to monthly, such as were deployed DGTs. The physiological status of mussels, the speciation of TEs between their dissolved and suspended-particulate phases, and their relative influence on TE bioaccumulation dynamics in mussels were investigated. In conclusion, these case studies properly demonstrate how DGT probes can be used as a relevant and complementary tool to bioindicators. Their concomitant use should therefore be privileged in monitoring surveys. [less ▲]

Detailed reference viewed: 37 (4 ULg)
Full Text
Peer Reviewed
See detailTrace metal speciation? An essential aspect of biomonitoring to avoid wrong conclusions
Richir, Jonathan ULg; Lepoint, Gilles ULg; Donnay, Annick et al

Poster (2015, September 29)

The Mediterranean mussel Mytilus galloprovincialis is widely used as a bioindicator species in active monitoring surveys. As a filter feeder artificially maintained in the water column, it bioaccumulates ... [more ▼]

The Mediterranean mussel Mytilus galloprovincialis is widely used as a bioindicator species in active monitoring surveys. As a filter feeder artificially maintained in the water column, it bioaccumulates trace metals from the surrounding water in their dissolved and particulate forms. However, most monitoring surveys don’t take into account that speciation aspect when studying trace metal accumulation kinetics in mussels. In the framework of the STARECAPMED project, we monitored trace metal concentrations in the flesh of mussels together with their “most bioavailable” dissolved and particulate fractions in the water column for almost 5 months (February-June 2011). Mussels were purchased from 2 little contaminated French shellfish farms (SARL Etang de Diane and ferme marine des Aresquiers), placed in several pouches to allow regular sampling, and immerged near the Oceanographic Research Station STARESO in the Calvi bay, northwestern Corsica. Mussels and water samples for suspended matter filtration were collected every week to two weeks, as were deployed DGTs. Seawater samples were filtered through 47 mm hydrophilic PTFE membrane filters with a 0.45 µm pore size until clogging. In the laboratory, mussel flesh and filters were digested in Teflon vessels with acids (HNO3/H202) in a closed microwave digestion lab station. DGT resins were eluted for 24h in 1.0 M HNO3. Trace metal concentrations (Cr, Mn, Co, Ni, Cu, Zn, Ag, Cd, Pb) were measured by DRC-ICP-MS. Analytical accuracy was checked by analyzing CRMs. All the studied metals except Pb and Zn were present in the water column to over 80% in their dissolved form. The contribution of the dissolved pathway was thus likely to be predominant in the oligotrophic Calvi bay. Dissolved trace metals showed little temporal variability of their levels, likely resulting from the integration over time of their levels in the DGT probes and the lack of seasonality of this fraction. In contrast, Zn showed great variability of its particulate fraction during the survey. Such temporal variability was also observed for Cr, more abundant in its particulate form at the end of the survey, and for Mn and Pb that conversely tended to decrease. The dynamic of trace metals in the mussel flesh is regulated by the environmental bioavailability of dissolved and particulate metals, the ecophysiological status of mussels and the trophic conditions of the water body. In the oligotrophic Calvi bay, showing background contamination levels by metals, the trophic conditions played a major role once out of the spring plankton bloom. It led to the increase of metal concentrations measured in the flesh of mussels undergoing starvation. However, some metals such as Cu and Co displayed only little temporal variations of their concentrations, these essential micronutrients being well regulated. The combined study of trace metal bioavailability and mussel ecophysiology in defined environmental conditions allows discriminating against biotic and abiotic factors regulating contaminant uptake in mussels, thus avoiding wrong conclusions about the observed dynamics of the studied contaminants. Mussels are a good proxy of coastal water quality, but their proper use notably requires adjustment of raw contaminant concentrations with trophic status of monitored sites. [less ▲]

Detailed reference viewed: 31 (2 ULg)
Full Text
Peer Reviewed
See detailComparison of isotopic turnover dynamics in two different muscles of a coral reef fish during the settlement phase
Gajdzik, Laura ULg; Lepoint, Gilles ULg; Lecchini, David et al

in Scientia Marina (2015), 79(3), 325-333

The temporal variation in carbon and nitrogen isotopic compositions (noted as δ13C and δ15N) was investigated in the convict surgeonfish (Acanthurus triostegus) at Moorea (French Polynesia). Over a period ... [more ▼]

The temporal variation in carbon and nitrogen isotopic compositions (noted as δ13C and δ15N) was investigated in the convict surgeonfish (Acanthurus triostegus) at Moorea (French Polynesia). Over a period of 24 days, juveniles were reared in aquaria and subjected to two different feeding treatments: granules or algae. The dynamics of δ13C and δ15N in two muscles (the adductor mandibulae complex and the epaxial musculature) having different functions were compared. At the end of experiments, a steady-state isotopic system in each muscle tissue was not reached. Especially for the algal treatment, we found different patterns of variation in isotopic compositions over time between the two muscles. The turnovers of δ13C showed opposite trends for each muscle but differences are mitigated by starvation and by the metamorphosis. Our study highlighted that the metabolism of coral reef fish may be subjected to catabolism or anabolism of non-protein precursors at settlement, inducing variation in isotopic compositions that are not linked to diet change. [less ▲]

Detailed reference viewed: 43 (7 ULg)
Full Text
Peer Reviewed
See detailSelective top-down control of epiphytic biomass by amphipods from Posidonia oceanica meadows: implications for ecosystem functioning
Michel, Loïc ULg; Dauby, Patrick ULg; Dupont, Alessandra et al

in Belgian Journal of Zoology (2015), 145(2), 83-93

Mediterranean Posidonia oceanica meadows shelter an important biomass and biodiversity of amphipod crustaceans that graze on epiphytes. However, their actual significance for ecosystem functional ... [more ▼]

Mediterranean Posidonia oceanica meadows shelter an important biomass and biodiversity of amphipod crustaceans that graze on epiphytes. However, their actual significance for ecosystem functional processes is hard to estimate, due to the lack of adequate data. Here, a field microcosm-based inclusion experiment was used to test if three of the dominant taxa of the amphipod community (Apherusa chiereghinii, Dexamine spiniventris and Gammarus spp.) could exert top-down control on seagrass leaf epiphytes. Influence of amphipod activity on nutrient availability for the host species was also investigated. All grazer taxa significantly reduced biomasses of erect macroalgae and erect sessile animals present on leaves. None of them consumed encrusting epiflora or epifauna. This selective top-down control could have important implications for the structure of the epiphytic community of P. oceanica leaves, which is one of the most diverse and abundant of all seagrass species. Grazing activity of all taxa caused higher N content of seagrass leaves, likely through amphipod excretion and/or sloppy feeding. Since P. oceanica meadows often grow in oligotrophic zones where plant growth can be nutrient-limited, this N enrichment could enhance seagrass production. Overall, the ecological interaction between P. oceanica and amphipods could be seen as a facultative mutualistic relationship. Our results suggest that amphipod mesograzers are key-elements in some of the functional processes regulating these complex and yet endangered ecosystems, which are essential components of Mediterranean coastal zones. [less ▲]

Detailed reference viewed: 115 (15 ULg)
Full Text
See detailSTARECAPMED (STAtion of Reference and rEsearch on Change of local and global Anthropogenic Pressures on Mediterranean Ecosystems Drifts) - Année 2014. Rapport de recherches.
Richir, Jonathan ULg; Abadie, Arnaud ULg; Binard, Marc ULg et al

Report (2015)

La prise de conscience, par le grand public, de l'impact grandissant de l'homme sur l'océan est récente. Elle se traduit par une volonté politique sincère de correction par des mesures de protection, de ... [more ▼]

La prise de conscience, par le grand public, de l'impact grandissant de l'homme sur l'océan est récente. Elle se traduit par une volonté politique sincère de correction par des mesures de protection, de gestion et de développement durable. Ces politiques, et leurs conséquences économiques et sociétales lourdes, ne peuvent être acceptées que si les décisions se fondent sur des connaissances scientifiques incontestables et montrent des résultats scientifiquement prouvés. Par ailleurs, ces décisions doivent prendre en compte des impacts qui s'opèrent à des échelles de temps et d’espace très variables, de quelques heures à plusieurs dizaines d’années et de quelques mètres à plusieurs milliers de km. En termes politiques, l'information scientifique nécessaire à la prise de décision doit pouvoir couvrir les différentes échelles depuis le niveau local et régional, jusqu'à l'échelle nationale, européenne voire globale, et cela sur le plus long terme possible. Enfin, pour être complète, l'information scientifique sur les écosystèmes marins doit pouvoir répondre à trois questions objectives : (i) quel est l'état? (ii) quelle est l'évolution? (iii) quels sont les mécanismes et processus mis en jeux? et à une question plus prospective : (vi) que peux-t-on prévoir et comment agir? Le présent rapport ne peut pas, à lui seul, refléter toute la richesse du programme STARECAPMED. En 3 ans, STARECAPMED a généré plusieurs centaines de milliers de données nouvelles, ré-exploité plusieurs centaines de publications, rapports et autres enregistrements passés et présents. Le programme a aussi généré de nombreux documents, rapports et mémoires. Enfin, des publications internationales et des thèses de doctorat sont en cours de réalisation ou abouties. Afin de rester lisible, nous avons donc choisi de présenter ce rapport 2014 sous la forme de 12 exemples parmi les travaux en cours. Ces exemples sont traités selon un schéma identique en 4 points simples : (i) La présentation du cas d’étude dans le projet global ; (ii),Les approches innovatrices développées ; (iii),La présentation de résultats marquants ; (iv),Les délivrables de STARECAPMED pour les politiques publiques. [less ▲]

Detailed reference viewed: 92 (36 ULg)
Full Text
See detailChanges of macrofauna stable isotope compositions in a very inconstant seagrass detritic habitat: actual diet modification or baseline shift?
Remy, François ULg; Mascart, Thibaud ULg; Dauby, Patrick ULg et al

Conference (2015, May 20)

Decayed leaves of the Neptune grass Posidonia oceanica, detached and then exported during storms, constitute an important compartment in terms of organic matter transfer from the seagrass bed to the other ... [more ▼]

Decayed leaves of the Neptune grass Posidonia oceanica, detached and then exported during storms, constitute an important compartment in terms of organic matter transfer from the seagrass bed to the other habitats, particularly coastal habitats. These exported litter accumulations (ELA) support a diverse (more than 130 species) and abundant (up to 4900 id.m-2) vagile macrofauna (invertebrates > 500µm) assemblage which may play a key role in the degradation, enrichment and carbon transfer from P. oceanica dead material to coastal food chains. Indeed, preliminary results of vagile invertebrates gut content observations show that even if only a few of these species ingest a large proportion of P.oceanica dead leaves fragments, most of the others ingest a small but non-negligible part, suggesting a potential role of the whole community in the mechanical fragmentation of the dead leaves. ELA are very dynamic habitats with highly variable food availability, quality, and composition. Such an inconstant habitat may result in drastic modifications of the invertebrate community but also of its trophic structure and ecology. To test this hypothesis of influence of pulsed availability, quality and composition of food sources on the vagile macrofauna diet, we took seasonal samples in Calvi Bay (Corsica, 8°45’E; 42°35’N), at two sites between August 2011 and May 2012. Stable isotopes analysis (C&N) were conducted at an individual level on dominant macrofauna species and mixing and isotopic niche model packages in R were used. Bayesian inference “SIBER” package highlighted significant seasonal and spatial differences of diet at the community, specific and even intraspecific level. Data confirm the potential transfer of seagrass material to animal tissues but in various proportions depending of the species and the season. But one question remained: are these variations reflection a true diet change, or only a spatiotemporal baseline variation of the food sources isotopic composition? “SIAR” Bayesian mixing model showed that it depends on the species and that the two responses co-occur. We emphasized the need to work at the specific level but also with an adequate temporal resolution for sampling to encompass diet and baseline variability. [less ▲]

Detailed reference viewed: 76 (5 ULg)
Full Text
See detailApplication of stable isotopes in trophic ecology: importance of TEF and seasonal baseline for robust interpretations.
Remy, François ULg; Darchambeau, François ULg; Dauby, Patrick ULg et al

Conference (2015, April 02)

Nitrogen, carbon and sulfur stable isotopes are very powerful tools for trophic ecologists to delineate food webs of various ecosystems. More recently… the use of mixing models has exponentially increased ... [more ▼]

Nitrogen, carbon and sulfur stable isotopes are very powerful tools for trophic ecologists to delineate food webs of various ecosystems. More recently… the use of mixing models has exponentially increased to give a more specific vision of organism’s diets and trophic relationships. Two case studies will be presented to give a summary of what’s been done in Liège Oceanology Lab to improve our interpretation of stable isotopes results. First is an experimental calculation of the Trophic Enrichment Factors (TEFs) for one dominant detritivorous species of Mediterranean amphipod inhabiting seagrass detritus: Gammarus aequicauda (Martynov, 1931). This experimental study was planned after a strange result of the SAIR mixing model, giving results opposed to all observations and knowledge we had about this species. Thus, the impact of 3 very different food sources (amphipod powder, algae power, seagrass powder) on the turnover rate of C and N isotopic compositions was tested, and afterwards TEFs for C and N for each source were calculated. Animal food source showed to be the most effectively assimilated with a fast turnover rate while seagrass and algae showed very slow assimilation. TEFs calculations showed to be interesting because TEFs seem not to depend on the natural feeding type of the invertebrate but more on the type of food source. Animal source showed carnivorous TEFs values while seagrass and algae source showed typical detritivorous values. SIAR results with these new custom values gave more coherent values highlighting the major importance of TEFs values for mixing models data interpretation. Second is a simple question: are the seasonal isotopic composition variations observed for many seagrass detritus macrofauna species due to actual diet changes, or only to isotopic baseline shift of the food sources? Macrofauna and all potential food sources were sampled near STARESO Oceanographic Station (Corsica, 8°45’E; 42°35’N) in 2011-2012 at each season at two different sites. SIBER software runs with C and N isotopic data showed spatio-temporal isotopic variations at community, interspecific and intraspecific level. SIBER did not gave us information about the origin of these changes, but coupled with SIAR and our custom TEFs, species actually showing drastic changes of diet were identified, while others seem to reflect more a source baseline isotopic composition shift. Working at specific level is compulsory for fine conclusions. These two case studies highlight the importance of mixing model use and of accurate TEF values to run these models properly to draw robust and reliable conclusions using stable isotopic data. [less ▲]

Detailed reference viewed: 172 (9 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: 108 (14 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: 93 (6 ULg)
Full Text
See detailEco-toxicological analysis of free-ranging cetaceans from the North-western Mediterranean Sea
Pinzone, Marianna ULg; Ody, Denis; Lepoint, Gilles ULg et al

Conference (2015, March 25)

The numerous anthropogenic activities occurring nowadays in the North-western Mediterranean Sea strongly affect top predators such as marine mammals, especially through the bioaccumulation of lipophilic ... [more ▼]

The numerous anthropogenic activities occurring nowadays in the North-western Mediterranean Sea strongly affect top predators such as marine mammals, especially through the bioaccumulation of lipophilic contaminants. In order to assess the eco-toxicological status of local living cetaceans blubber biopsies were collected between 2006 and 2013. Selected persistent organic pollutants POPs (31PCBs, 15 organochlorine compounds, 9 PBDEs and 17 PCDD/Fs) were analyzed in 49 long-finned pilot whales Globicephala melas, 61 sperm whales Physeter macrocephalus and 70 fin whales Balaenoptera physalus. δ13C, δ15N values and POPs levels were assessed through IR-MS and GC-MS respectively. To assess the toxic potency of the dioxin-like compounds, the TEQ approach was applied. δ15N values were 12.2±1.3‰ for sperm whales, 10.5±0.7‰ for pilot whales and 7.7±0.8‰ in fin whales, positioning sperm whales at higher trophic levels. δ13C instead was similar and amounted to −17.3±0.4‰, −17.8±0.3‰ and −18.7±0.4‰ respectively. Pilot whales presented higher concentrations than sperm whales for ΣPCBs (38666±25731ng.g-1 lw and 22849±15566ng.g-1 lw respectively), ΣPBDEs (712±412ng.g-1 lw and 347±173ng.g-1 lw respectively) and ΣDDTs (46081±37506ng.g-1 lw and 37647±38518ng.g-1 lw respectively). Fin whales presented the lowest values, in accordance with its trophic position (ΣPCBs: 5721±5180ng.g-1 lw, ΣPBDEs: 177±208ng.g-1 lw and ΣDDTs: 6643±5549ng.g-1 lw). The PCA analysis confirmed how p,p’DDT and p,p’DDE were influential in differentiating the species, as a consequence of their migratory behavior and distribution. Pollutant concentrations were significantly higher than both their Southern Hemisphere and North Atlantic counterparts, possibly due to the particular Mediterranean geomorphology, which influences pollutants distribution and recycle. Dioxin-like  PCBs accounted for over 80% of the total TEQ. This study demonstrated (1) an important exposure to pollutants of Mediterranean toothed-whales, often surpassing the estimated threshold toxicity value of 17000ng.g−1 lw for blubber in marine mammals; and (2) how their geographical distribution can influence the pollutants profile and concentrations. [less ▲]

Detailed reference viewed: 53 (5 ULg)
Full Text
Peer Reviewed
See detailHow do harpacticoid copepods colonize detrital seagrass leaves?
Mascart, Thibaud ULg; Agusto, Laura; Lepoint, Gilles ULg et al

in Marine Biology (2015), 162(5), 929-943

An experiment was carried out investigating the colonization ability and specific pattern of copepods towards a provisional benthic habitat. Since copepods are known to disperse passively and actively ... [more ▼]

An experiment was carried out investigating the colonization ability and specific pattern of copepods towards a provisional benthic habitat. Since copepods are known to disperse passively and actively, the experiment aimed to investigate the pool of colonizers of macrophytodetritus and the species-specific active colonization pathways. The experiment was performed in a Mediterranean seagrass Posidonia oceanica meadow on defaunated macrophytodetritus accumulations (mainly dead seagrass leaves) for two time intervals (24 h and 96 h). Active colonization by copepods, independently of their adjacent potential source pool habitat (bare sandy sediments, P. oceanica canopy, water column and macrophytodetritus) occurred within 24 h. Natural densities (as in the control treatments) were only reached by active colonization through the water column. Both neither diversities nor species composition of natural macrophytodetritus were ever reached by one single migratory pathway, therefore only a combination of interstitial migration and water column migration can explain the species occurrence under natural condition. Moreover, every potential adjacent source pool habitat, contributed species to the newly colonized macrophytodetritus. However, the main colonizers were mostly species with good swimming capabilities. The diverse pool of species present in the newly colonized macrophytodetritus underlines the complex communities and dispersion capabilities of copepods. Hence, macrophytodetritus possesses the potential ability to be a colonizer source pool for every adjacent habitat and thus behaves as a copepod hub for the entire seagrass ecosystem. [less ▲]

Detailed reference viewed: 37 (11 ULg)
Full Text
See detailInfluences of blubber composition and profile in the assessment of POPs levels in free-ranging cetaceans
Pinzone, Marianna ULg; Budzinski, Hélène; Tasciotti, Aurelie et al

Poster (2015, February 28)

Investigating the food and feeding ecology of free-ranging cetaceans has always been very challenging. Still now, mass stranding events represent almost the only opportunity to collect valid information ... [more ▼]

Investigating the food and feeding ecology of free-ranging cetaceans has always been very challenging. Still now, mass stranding events represent almost the only opportunity to collect valid information on these large and elusive animals. Biopsy darting is a non-lethal tissue sampling technique which permits the collection of tissues from living and healthy individuals. However, important discussions exist about how efficient this method is in chemical analyses where the percentage lipid content of the tissue is of great importance. Biopsies of skin and blubber were conducted on 49 long-finned pilot whales (Globicephala melas), 61 sperm whales (Physeter macrocephalus) and 70 fin whales (Balaenoptera physalus) in the North Western Mediterranean Sea (NWMS) from 2006 to 2013. Lipid content, δ13C, δ15N values and ΣPCBs were analysed and compared with previous studies conducted on stranded and biopsied individuals. Lipids extraction was operated via ASE; δ13C, δ15N values and POPs levels were assessed through IR-MS and GC-MS respectively. δ15N values were 12.2±1.3‰ for sperm whales, 10.5±0.7‰ for pilot whales and 7.7±0.8‰ in fin whales, positioning sperm whales at higher trophic levels. δ13C instead was similar and amounted to −17.3±0.4‰, −17.8±0.3‰ and −18.7±0.4‰ respectively. Pilot whales presented the highest concentrations of ΣPCBs (38666 ± 25731ng.g-1 lw) followed by sperm whales (22849 ± 15566ng.g-1 lw) and fin whales (5721±5180ng.g-1 lw). Lipids percentage differed significantly between species. Sperm whales showed the lowest lipid content with an average of 12±9%, whereas for long-finned pilot whales it was 22±21% and for fin whales 31±14%. Lipid content of the two odontocetes varied between years of sampling, whilst for fin whales remained similar. The PCBs concentrations, especially in sperm whales, were in discordance with previous studies conducted in the same area and our δ13C, δ15N values. We hypothesized that (1) the extreme low lipid content found in the blubber, (2) the extraction procedure and (3) the biopsies technique, could explain such different pattern. Several papers demonstrated how POPs concentrations in cetaceans blubber are strongly influenced by its thickness, stratification and lipid profile. Therefore, the particular characteristics of blubber composition of deep—diving income breeders such as sperm whales, may not allow an efficient representation of POPs concentrations through the use of biopsies. [less ▲]

Detailed reference viewed: 28 (5 ULg)
Full Text
Peer Reviewed
See detailSeasonal variability of meiofauna, especially harpacticoid copepods, in Posidonia oceanica macrophytodetritus accumulations
Mascart, Thibaud ULg; Lepoint, Gilles ULg; Deschoemaeker, Silke et al

in Journal of Sea Research (2015), 95

The overall aim of this study was (1) to assess the diversity and density of meiofauna taxa, especially harpacticoid copepod species, present within accumulated seagrass macrophytodetritus on unvegetated ... [more ▼]

The overall aim of this study was (1) to assess the diversity and density of meiofauna taxa, especially harpacticoid copepod species, present within accumulated seagrass macrophytodetritus on unvegetated sand patches and (2) to elucidate the community structure of detritus-associated harpacticoid copepods in relation to natural temporal variability of physico-chemical characteristics of accumulations. This was investigated in a Posidonia oceanica (L.) Delile seagrass ecosystem in the northwest Mediterranean Sea (Bay of Calvi, Corsica, 42°35’N, 8°43’E) using a triplicate macrophytodetritus core field sampling in two contrasting sites over the four seasons of 2011. Meiofauna higher taxa consisted of 50% Copepoda, which 87% belonged to the Harpacticoida order. Nematoda was the second most abundant taxa. The copepod community displayed a wide variety of morphologically similar and ecologically different species (i.e. mesopsammic, phytal, phytal-swimmers, planktonic and parasitic). The harpacticoid copepod community followed a strong seasonal pattern with highest abundances and species diversity in May-August, revealing a link with the leaf litter epiphyte primary production cycle. Aside from the important role in sheltering, housing and feeding potential of macrophytodetritus, a harpacticoid community BEST analysis demonstrated a positive correlation with habitat complexity and a negative correlation with water movements and P. oceanica leaf litter accumulation. [less ▲]

Detailed reference viewed: 80 (22 ULg)
Full Text
Peer Reviewed
See detailEarly colonization on Artificial Seagrass Units and on Posidonia oceanica (L.) Delile leaves
Pete, Dorothée ULg; Lepoint, Gilles ULg; Bouquegneau, Jean-Marie ULg et al

in Belgian Journal of Zoology (2015), 145(1), 59-68

Many epiphytes grow on Posidonia oceanica (L.) Delile leaves but early stages of that colonization are not well known. To study this early colonization without destroying the plant, Artificial Seagrass ... [more ▼]

Many epiphytes grow on Posidonia oceanica (L.) Delile leaves but early stages of that colonization are not well known. To study this early colonization without destroying the plant, Artificial Seagrass Units (ASUs) were utilised. The first nine days of colonization by macroscopic eukaryotic organisms on natural P. oceanica leaves and on ASUs were studied. The capability of those ASUs to mimic P. oceanica in the long term was also evaluated. Indeed, early colonists of a substrate can influence the settling of later ones by “priority effects”. Thus if the pioneer community is the same on both substrates, they will more likely be the same after a longer exposure time. On both substrates, colonization began by the settling of crustose-calcareous algae and foraminiferans. The number of organisms increased more quickly on ASUs than on natural leaves but Shannon-Wiener diversity index was higher for P. oceanica leaves. The low colonization rate on natural leaves may have been due to different microclimatic conditions on the two substrates and to a less developed biofilm than on ASUs. The high diversity observed on natural leaves was mainly related to the presence of bryozoan ancestrulae, which were absent on ASUs. Different microhabitats on each substrate (different algae morphotypes) can explain this difference. Thus, at such an early colonization stage, pioneer communities were different on the two substrates, suggesting that later communities would be different too. However, ASUs could be used in environmental perturbation studies instead of natural leaves, thanks to their high colonization rate. [less ▲]

Detailed reference viewed: 56 (6 ULg)