References of "Lepoint, Gilles"
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See detailCarbon cycling in the mixolimnion of Lake Kivu : results from the CAKI project
Borges, Alberto ULg; Descy, Jean-Pierre; Delille, Bruno ULg et al

Conference (2009, January 19)

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See detailEvidence for wastewater influence in a low impacted area throughout stable isotope analyses of the limpet Patella caerulea and epilithic biofilms
Vermeulen, Simon ULg; Lepoint, Gilles ULg; Gobert, Sylvie ULg

Poster (2009, January)

Eutrophication is considered to be one of the main threats to marine environments leading to changes in trophic status of ecosystems and alteration of biological diversity. Carbon and Nitrogen stable ... [more ▼]

Eutrophication is considered to be one of the main threats to marine environments leading to changes in trophic status of ecosystems and alteration of biological diversity. Carbon and Nitrogen stable isotopes analyses were performed on the limpet Patella caerulea and one of its food sources (epilithic biofilms) to assess their potential as early indicators of eutrophication. Samples were seasonally collected in 2005-2006 on five locations gradually exposed to urban sewage in the Calvi Bay and in the Marseilles harbour. Stable isotope signatures of Patella caerulea muscles exhibited steady site - specific values over seasons. In contrast to this time – integrated signal, wide variations in biofilm values show that either composition or isotopic ratios of food sources may vary greatly in time and space. Elevated δ15N values of limpets and biofilms, typical of wastewater influence but unrelated to nitrogen loads, indicate the biological availability of sewage-derived nitrogen in the Calvi Bay and the Marseilles harbour. A reference level of δ15N values is rapidly reached with increasing depth that indicates the limited vertical extent of pollution in the Calvi Bay. [less ▲]

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See detailSeed nutrient content and nutritional status of Posidonia oceanica seedlings in the northwestern Mediterranean Sea
Balestri, Elena; Gobert, Sylvie ULg; Lepoint, Gilles ULg et al

in Marine Ecology. Progress Series (2009), 388

Successful seedling establishment is rare in Posidonia oceanica. The first year after germination is likely to be the most critical phase in the recruitment process, but little is still known on the ... [more ▼]

Successful seedling establishment is rare in Posidonia oceanica. The first year after germination is likely to be the most critical phase in the recruitment process, but little is still known on the factors affecting seedling survival. Mature fruits of P. oceanica released from a meadow of the north-western Mediterranean were deposited by currents on the adjacent beach in May 2004. In May and December 2005, some seedlings established in the previous summer were uprooted by storms and deposited on the beach. This material provided the opportunity to examine seed mass and nutrient content, and the nutritional status of seedlings. Our findings support the hypothesis that growth limitation may be an important cause of mortality for seedlings during the first year of establishment in poor-nutrient sites. [less ▲]

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See detailTrophic niches of thirteen damselfishes (Pomacentridae) at the Grand Récif of Toliara, Madagascar
Frederich, Bruno ULg; Fabri, Grégory ULg; Lepoint, Gilles ULg et al

in Ichthyological Research (2009), 56

The damselfishes, with more than 340 species, constitute one of the most important families that live in the coral reef environment. Most of our knowledge of reef-fish ecology is based on this family, but ... [more ▼]

The damselfishes, with more than 340 species, constitute one of the most important families that live in the coral reef environment. Most of our knowledge of reef-fish ecology is based on this family, but their trophic ecology is poorly understood. The aim of the present study was to determine the trophic niches of 13 sympatric species of damselfishes by combining stable isotope (d15N and d13C) and stomach content analyses. Isotopic signatures reveal three main groups according to their foraging strategies: pelagic feeders (Abudefduf sexfasciatus, A. sparoides, A. vaigiensis, Chromis ternatensis, C. dimidiata, Dascyllus trimaculatus and Pomacentrus caeruleus), benthic feeders (Chrysiptera unimaculata, Plectroglyphidodon lacrymatus and Amphiprion akallopisos) and an intermediate group (D. aruanus, P. baenschi and P. trilineatus). Stomach contents reveal that planktonic copepods and filamentous algae mainly represent the diets of pelagic feeders and benthic feeders, respectively. The intermediate position of the third group resulted from a partitioning of small planktonic prey, small vagile invertebrates and filamentous algae. In this last feeding group, the presence of a wide range of d13C values in P. trilineatus suggests a larger trophic niche width, related to diet-switching over time. Some general considerations about the feeding habits of damselfishes reveal that their choice of habitat on the reef and their behavior appear to be good predictors of diet in this group. Benthic (algae and/or small invertebrates) feeders appear to be solitary and defend a small territory on the bottom; zooplankton feeders remain in groups just above the reef, in the water column. [less ▲]

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See detailNiche differentiation among neotropical soldierless soil-feeding termites revealed by stable isotope ratios
Bourguignon, Thomas; Sobotnik, Jan; Lepoint, Gilles ULg et al

in Soil Biology & Biochemistry (2009), 41

Termites represent one of the most abundant belowground animal taxa in tropical rainforests, where their species richness is much higher than in any other ecosystem. This high diversity in soil ecosystems ... [more ▼]

Termites represent one of the most abundant belowground animal taxa in tropical rainforests, where their species richness is much higher than in any other ecosystem. This high diversity in soil ecosystems is however difficult to explain by classical Hutchinsonian niche theory, as there is little evidence for spatial or temporal separation between species. Using δ13C and δ15N isotopic ratios, we tested if resource partitioning along the humification gradient occurs in neotropical soldierless termites of the Anoplotermes-group. Two distinct sites were investigated to check if interspecific differences are transposable between sites. Significant differences in δ15N were found between species of the Anoplotermes-group. Although some species displayed higher intersite δ15N variation than others, species-average δ15N values for both sites were highly correlated, showing that sympatric soldierless soil-feeding termites feed on distinct components of the soil. Our data also suggest that some species are more likely to shift along this gradient than others, in response to overall habitat conditions or to the presence of competitors. Feeding niche differentiation can therefore account for the high species richness and diversity of soldierless soil-feeding termites in neotropical rainforests. [less ▲]

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See detailTrophic relationships in a tropical stream food web assessed by stable isotope analysis
Coat, Sophie; Monti, Dominique; Bouchon, Claude et al

in Freshwater Biology (2009), 54(5), 1028-1041

1. Stable isotope analysis, coupled with dietary data from the literature, was used to investigate trophic patterns of freshwater fauna in a tropical stream food web (Guadeloupe, French West Indies). 2 ... [more ▼]

1. Stable isotope analysis, coupled with dietary data from the literature, was used to investigate trophic patterns of freshwater fauna in a tropical stream food web (Guadeloupe, French West Indies). 2. Primary producers (biofilm, algae and plant detritus of terrestrial origin) showed distinct delta C-13 signatures, which allowed for a powerful discrimination of carbon sources. Both autochthonous (C-13-enriched signatures) and allochthonous (C-13-depleted signatures) resources enter the food web. The migrating behaviour of fishes and shrimps between marine and freshwater during their life cycles can be followed by carbon isotopes. Here, shrimp delta C-13 signatures were shown to shift from -16 parts per thousand (for juveniles under marine influence) to -24.7 parts per thousand (for adults in freshwater habitats). For resident species, delta C-13 values partly reflected the species' habitat preferences along the river continuum: species living in river mouths were C-13-enriched in comparison with those collected upstream. 3. Nitrogen isotopic ratios were also discriminating and defined three main trophic guilds among consumers. The delta N-15 values of herbivores/detritivores were 5.0-8.4 parts per thousand, omnivores 8.8-10.2 parts per thousand and carnivores 11-12.7 parts per thousand. 4. Mixing model equations were employed to calculate the possible range of contribution made by respective food sources to the diet of each species. The results revealed the importance of omnivorous species and the dependence of riverine biota on terrestrial subsidies, such as leaf detritus and fruits. Finally, the abundance of shrimps and their feeding habits placed in relief their key role in tropical freshwater food webs. Isotopic analysis provides a useful tool for assessing animal feeding patterns. [less ▲]

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See detailCarbon cycling in the mixolimnion of Lake Kivu (East Africa)
Borges, Alberto ULg; Descy, J.-P.; Delille, Bruno ULg et al

Poster (2009)

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See detailCarbon cycling in the mixolimnion of Lake Kivu (East Africa)
Borges, Alberto ULg; Descy, J.-P.; Delille, Bruno ULg et al

Conference (2009)

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See detailCarbon cycling in the mixolimnion of Lake Kivu (East Africa)
Borges, Alberto ULg; Descy, J.-P.; Delille, Bruno ULg et al

Poster (2009)

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See detailTrophic diversity among amphipod crustaceans from Posidonia oceanica meadows : A stable isotope assessment
Michel, Loïc ULg; Lepoint, Gilles ULg; Gobert, Sylvie ULg et al

Conference (2008, October 31)

Vagile invertebrates are regarded as key-components of Posidonia oceanica meadow ecosystems, particularly in organic matter transfers from primary producers to higher level consumers. Among these ... [more ▼]

Vagile invertebrates are regarded as key-components of Posidonia oceanica meadow ecosystems, particularly in organic matter transfers from primary producers to higher level consumers. Among these invertebrates, amphipod crustaceans are one of the most abundant and diverse groups, and probably play an important role in meadow ecosystem functioning. However, their trophic ecology is poorly known, and these crustaceans are generally regarded as vegetal epiphytes consumers or generalist detritivores, due to the lack of accurate studies. Here, we focused on the study of the interspecific trophic diversity, and on the importance of other food sources (Posidonia leaves and litter, animal epiphytes, suspended particular organic matter, …) in those amphipods’ diet. To assess these phenomena, we used stable isotopes ratios of carbon and nitrogen as trophic tracers. It appears that, while some species (such as Apherusa chiereghinii and Aora spinicornis) seem to feed mainly on epiphytes, others, like Dexamine spiniventris, exploit different food sources. These results thus tend to show that amphipod trophic diversity could have been underestimated in the past. Moreover, they enhance the comprehension of the feeding ecology of these animals, and therefore of the way they interact with the Posidonia meadow ecosystem. [less ▲]

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See detailMulti-scale spatial variability of amphipod assemblages from the foliar stratum of the Posidonia oceanica (L.) Delile meadow
Sturaro, Nicolas ULg; Lepoint, Gilles ULg; Michel, Loïc ULg et al

Conference (2008, October)

Studying spatial patterns is of ecological importance in order to understand the causes of the distribution and abundance of organisms, and it also provides valuable basis for management and conservation ... [more ▼]

Studying spatial patterns is of ecological importance in order to understand the causes of the distribution and abundance of organisms, and it also provides valuable basis for management and conservation. In the Mediterranean coastal zone, the Posidonia oceanica seagrass meadows constitute one of the dominant ecosystems and are an important habitat for vagile invertebrates. Among these, amphipods comprise a large number of species, with considerable abundance and biomass, as well as being an important trophic resource for fish populations. Until now, little attention has been given to the horizontal variability at different spatial scales of amphipod assemblages associated with P. oceanica meadows. A hierarchical sampling design, spanning three orders of magnitude (from 1 to 100s of metres) was elaborated. Sampling was undertaken in March 2007 in the meadows of Calvi Bay (NW Corsica), at depths ranging from 10 to 13 m, using a suction sampler. Our results indicated an important horizontal variability of the studied assemblage, and this at different spatial scales. In addition, these results tend to show that the small scale (~ 1 m and ~ 10 m) influenced abundance, while the medium-scale (~ 100 m) influenced diversity. Some potential causes of the observed patterns are discussed. These results emphasize the importance of considering different spatial scales in the study of the vagile invertebrates associated with P. oceanica meadows. [less ▲]

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See detail15th Benelux Congress of Zoology abstract book
Colleye, Orphal ULg; Dauby, Patrick ULg; Fabri, Gregory et al

Book published by Editions de l'université de Liège (2008)

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See detailCarbon dioxide dynamics in lake Kivu during the dry and wet seasons
Borges, Alberto ULg; Delille, Bruno ULg; Descy, J.-P. et al

Poster (2008, April)

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See detailDistribution of trace elements in organs of six species of cetaceans from the Ligurian Sea (Mediterranean), and the relationship with stable carbon and nitrogen ratios
Capelli, R.; Das, Krishna ULg; De Pellegrini, R. et al

in Science of the Total Environment (2008), 390

Mercury (total and organic), cadmium, lead, copper, iron, manganese, selenium and zinc concentrations were measured in different organs of 6 different cetacean species stranded in an area of extraordinary ... [more ▼]

Mercury (total and organic), cadmium, lead, copper, iron, manganese, selenium and zinc concentrations were measured in different organs of 6 different cetacean species stranded in an area of extraordinary ecological interest (Cetaceans’ Sanctuary of the Mediterranean Sea) along the coast of the Ligurian Sea (North-West Mediterranean). Stable-isotopes ratios of carbon (13C/12C) and nitrogen (15N/14N) were also measured in the muscle. A significant relationship exists between 15N/14N, mercury concentration and the trophic level. The distribution of essential and non-essential trace elements was studied on several organs, and a significant relationship between selenium and mercury, with a molar ratio close to 1, was found in the cetaceans’ kidney, liver and spleen, regardless of their species. High selenium concentrations are generally associated with a low organic to total mercury ratio. While narrow ranges of concentrations were observed for essential elements in most organs, mercury and selenium concentrations are characterised by a wide range of variation. Bio-accumulation and bio-amplification processes in cetaceans can be better understood by comparing trace element concentrations with the stable-isotopes data. [less ▲]

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See detailIsotopic ratios and elemental contents as indicators of seagrass C processing and sewage influence in a tropical macrotidal ecosystem (Madagascar, Mozambic channel)
Lepoint, Gilles ULg; Frederich, Bruno ULg; Gobert, Sylvie ULg et al

in Scientia Marina (2008), 72(1), 109-117

Isotopic ratios and elemental concentrations of carbon and nitrogen were measured in seven seagrass species colonising different tidal flats near Toliara (SW Madagascar) in order to determine the ... [more ▼]

Isotopic ratios and elemental concentrations of carbon and nitrogen were measured in seven seagrass species colonising different tidal flats near Toliara (SW Madagascar) in order to determine the potential use of these parameters for assessing C processing and sewage use by tropical seagrasses. Nitrogen concentrations measured in upper intertidal seagrasses near Toliara were almost twice those measured on the tidal flat near a healthy mangrove situated 20 km away from Toliara town. At Toliara Beach, δ15N values were correlated with the N concentrations of Halodule sp., one of the dominant species on the tidal flat. This correlation did not exist for Halophila ovalis, the other dominant species. An increase in N concentrations and δ15N values demonstrates the influence of sewage coming directly onto Toliara Beach on the N cycles of intertidal seagrasses. Nevertheless, this influence seems restricted to the upper littoral zone and was not the main cause of seagrass die-off. On the other hand, at the mangrove site, δ15N values were not correlated with the N concentrations of Halodule sp. or Thalassia hemprichii, showing that natural δ15N variability is driven by other factors than the δ15N of N sources. Moreover, inter-individual variability of δ15N values was greater than inter-specific or inter-site variability, making the δ15N difficult to interpret in the context of human-disturbance influence on the N cycle of tropical seagrasses. δ13C values were close to -9‰, indicating the use of HCO 3– as an inorganic carbon source by the seven investigated species. Contrary to our hypothesis, variation between sites and location on the tidal flat was limited, suggesting limited impact on δ13C values of sewage, emersion duration and mechanisms for HCO 3– incorporation. [less ▲]

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See detailDiet and foraging ecology of Roseate terns and lesser noddies breeding sympatrically on Aride Island, Seychelles
Monticelli, David; Ramos, J. A.; Tavares, P. C. et al

in Waterbirds (2008), 31(239), 248

Inferences on seabird ecology from stable isotopes ratios (δ13C, δ15N) and mercury concentrations analysis of feathers have been made for temperate and polar species but are far more rare for tropical ... [more ▼]

Inferences on seabird ecology from stable isotopes ratios (δ13C, δ15N) and mercury concentrations analysis of feathers have been made for temperate and polar species but are far more rare for tropical species. In this paper, we used this approach combined with analysis of regurgitations and feeding observations at colonies to examine diet segregation between Roseate Terns (Sterna dougallii) and Lesser Noddies (Anous tenuirostris) breeding sympatrically on Aride Island (Seychelles), western Indian Ocean. Our results indicated extensive overlap between the two species in trophic level and foraging area during the breeding season. Goatfish predominated (93-97%) in all diet samples of adults and chicks collected in the colonies, except in prey fed to mates by Roseate Terns, of which scad and tuna comprised 20%. The isotopic analyses of feathers replaced by adults during molt (primary and body feathers) suggested, however, that the two species differ in foraging ecology during the nonbreeding period. Roseate Tern adults had consistently lower δ15N values than Lesser Noddies which, in turn, had δ15N values comparable to those of chick feathers grown on Aride. Moreover, low but similar mercury levels were found in body feathers of Lesser Noddy adults and Roseate Tern chicks, whereas Roseate Tern adults were significantly more contaminated. Overall, these results support the hypothesis that the Lesser Noddy is largely sedentary, being associated with the same food web in the vicinity of the colonies year-round. In contrast, Roseate Terns rely on distinct prey during the molting (nonbreeding) season which may be also consistent with a change in food web (i.e., a migratory regime) although the assignment of potential wintering areas remain difficult without isotopic basemaps currently available for the Indian Ocean. [less ▲]

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See detailPCDD, PCDF AND PCB DETERMINATION IN DOLPHINS REVEALS A WORLD HOTSPOT FOR PCBS IN GUANABARA BAY, BRAZIL
Dorneles, Paulo; Lailson-Brito, José; Eppe, Gauthier ULg et al

in Organohalogen Compounds (2008), 70

The main objective of the present study was to determine the current concentrations of PCDDs, PCDFs and PCBs in dolphins from a region of high industrialization and urbanization in the Southern Hemisphere ... [more ▼]

The main objective of the present study was to determine the current concentrations of PCDDs, PCDFs and PCBs in dolphins from a region of high industrialization and urbanization in the Southern Hemisphere. Since most of these compounds biomagnify in food chains and changes in ratios of stable isotopes of nitrogen (15N/14N) have been used to elucidate trophic relationships 7, measurements of these isotopes have been carried out in marine tucuxi dolphins and their prey in Guanabara Bay. Stable isotopes were measured, firstly, to quantitatively assess the trophic level of the dolphin, and, secondly, to provide information for future human risk assessment investigations related to fish consumption [less ▲]

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See detailLINK BETWEEN MARINE MAMMAL EXPOSURE TO PERFLUOROOCTANE SULFONATE (PFOS) AND STABLE-CARBON ISOTOPE RATIOS IN NERITIC AND OCEANIC WATERS OFF BRAZIL
Dorneles, Paulo; Lailson-Brito, José; Meyer, Johan et al

in Organohalogen Compounds (2008), 70

The main objective of the present study was to determine the current concentrations of PFOS in dolphins from neritic and oceanic waters of a region of high industrialization and urbanization in the ... [more ▼]

The main objective of the present study was to determine the current concentrations of PFOS in dolphins from neritic and oceanic waters of a region of high industrialization and urbanization in the Southern Hemisphere. Since stable carbon isotopes can be used to point out relative contributions to the diet of different potential primary sources in trophic networks, indicating for example the inshore versus offshore contribution to food intake 7,8, stable carbon isotope measurements were carried out in the same dolphins in order to clarify inter-species differences. [less ▲]

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See detailLactation effect on the trace element dynamics in northern elephant seals (Mirounga angustirostris)
Habran, Sarah ULg; Debier, Cathy; Lepoint, Gilles ULg et al

Conference (2007, November 30)

Northern elephant seals, Mirounga angustirostris, are exceptional mammals: females fast entirely during nursing while their pups may quadruple in weight over the 25-day suckling period. Females thus lose ... [more ▼]

Northern elephant seals, Mirounga angustirostris, are exceptional mammals: females fast entirely during nursing while their pups may quadruple in weight over the 25-day suckling period. Females thus lose approximately a third of body mass and produce energy-rich milk with a high fat content. Stable carbon and nitrogen isotope ratios (d13C and d15N used as diet markers) and total mercury concentrations (Hg) were measured in tissues (blood cells, serum, full blood, milk and blubber) from 20 mother-pup pairs on days 4 and 21 of lactation. A systematic difference was observed between isotopic values in blood cells and serum of the mothers, linked to diet and distinct biochemical composition between blood components. d13C differed between inner and outer blubber layers and were similar between inner blubber and milk. High Hg concentrations (up to 350 ng.g-1ww at the beginning of lactation) were found in the blood of mother elephant seals linked to their high d15N values in blood cells. Hg transfer through placenta and milk was observed between mothers and pups. A significant increase of blood Hg concentration in mothers (+285 ng.g-1ww) and a decrease in pups (-93 ng.g-1ww) were observed between days 4 and 21 of lactation. Both processes were explained by a remobilization of proteins and lipids during fasting and milk production in mothers and by a dilution of Hg in pups due to their high mass increase during this period. This study confirms that lactation modifies stable nitrogen isotope ratios in tissues, as well as mercury levels in blood from mothers and pups, and highlights the existence of a transplacental and transmammary transfer of mercury in northern elephant seals. Therefore, physiological processes and body condition should be considered carefully when interpreting stable isotope ratios and Hg concentrations in the framework of biomonitoring. [less ▲]

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See detailNocturnal vertical migrations by amphipods of the Posidonia oceanica (L.) Delile foliar stratum : Importance of the litter cover
Michel, Loïc ULg; Sturaro, Nicolas ULg; Lepoint, Gilles ULg et al

Poster (2007, November)

In seagrass meadows, several groups of vagile invertebrates are well known to perform a nocturnal rise from the lower layers of the meadow to the foliar stratum. This vertical migration is generally ... [more ▼]

In seagrass meadows, several groups of vagile invertebrates are well known to perform a nocturnal rise from the lower layers of the meadow to the foliar stratum. This vertical migration is generally regarded as a defense mechanism against predation by diurnal fishes, as well as a mean to maximize the exploitation of trophic resources offered by the meadow. Here, we focused on the amphipods from a Mediterranean Posidonia oceanica meadow. We sampled the community present in the meadows of Calvi Bay (NW Corsica) using two different techniques (hand-towed net and litter collecting). Samples were taken at two seasons, during both night and daytime. Our results confirm the nocturnal rise to the foliar stratum. Combined to an analysis of the recent literature, they also tend to show that amphipods spend the daytime not in the matte itself, as it has been proposed in the past, but in the thin layer of Posidonia litter present at the interface between the foliar stratum and the root/rhizome system. This would emphasize the role of the litter cover in the complexity of the habitat within the meadow, and therefore in the vagile invertebrate community structure and the functioning of the whole meadow as an ecosystem. [less ▲]

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