References of "Lepoint, Gilles"
     in
Bookmark and Share    
Full Text
Peer Reviewed
See detailTrophic niche width, shift, and specialization of Dascyllus aruanus in Toliara lagoon, Madagascar
Frederich, Bruno ULg; Lehanse, Olivier; Vandewalle, Pierre ULg et al

in Copeia (2010), 2010(2), 218-226

Intrapopulation diet specializations may result from the use of different dietary items or foraging tactics by individuals within a single population. The damselfish, Dascyllus aruanus, is a highly site ... [more ▼]

Intrapopulation diet specializations may result from the use of different dietary items or foraging tactics by individuals within a single population. The damselfish, Dascyllus aruanus, is a highly site-attached coral reef fish living in size hierarchies among branched corals. The trophic niche width and feeding specialization of this species were explored using stable isotopes and stomach content analyses. Intra-group niche variation was mainly related to fish size. Within social groups, D. aruanus gradually shifted its foraging tactics according to size; smaller fish fed on benthic prey such as isopods and copepods, and the larger fish foraged in the water column on planktonic copepods and larger-sized prey. Group density was found to explain some variation in trophic niche characteristics; greater specialization on prey size was observed in the colony having the highest density. All members of the largest colony foraged more frequently in the water column. Knowing that planktonic copepods are more energy-rich than benthic ones, a positive group-size effect facilitating access to preferred prey is suggested. Group size and group density effects on trophic specialization did not have any impact on body condition, suggesting that the behavioral plasticity of D. aruanus in its foraging strategies permits compensation for the maintenance of body conditions. [less ▲]

Detailed reference viewed: 87 (4 ULg)
Full Text
Peer Reviewed
See detailTrophic diversity of idoteids (Crustacea, Isopoda) inhabiting the Posidonia oceanica litter
Sturaro, Nicolas ULg; Caut, Stéphane; Gobert, Sylvie ULg et al

in Marine Biology (2010), 157(2), 237-247

The coexistence of three idoteid species in Posidonia oceanica litter raises the question of trophic diversity and their role in the litter degradation process. Hence, diet composition of Idotea balthica ... [more ▼]

The coexistence of three idoteid species in Posidonia oceanica litter raises the question of trophic diversity and their role in the litter degradation process. Hence, diet composition of Idotea balthica, Idotea hectica and Cleantis prismatica was studied using a combination of gut contents and stable isotopes analysis. Gut content observations indicate that P. oceanica dead leaves are an important part of the ingested food for the three species, although their tissues are constituted of only a small to medium fraction of P. oceanica carbon. Our results also underlined the potential role of these species in the degradation of P. oceanica litter by mechanically fragmenting the litter and by assimilating a small to medium fraction of carbon. Moreover, we showed that there were considerable inter- and intra-specific differences in diet composition. Diet differed between juveniles and adults for I. balthica. Crustaceans are an important food source for adults of I. balthica, while I. hectica indicated a major contribution of algal material. C. prismatica showed an intermediate diet. This trophic diversity is probably one of the factors allowing these species to coexist in the same biotope. [less ▲]

Detailed reference viewed: 79 (17 ULg)
See detailFood and feeding of Limnothrissa miodon and Lamprichthys tanganicanus in Lake Kivu
Masilya, M Pascal; Isumbisho, Mwapu Pascal; Darchambeau, François ULg et al

Poster (2010, January 13)

Detailed reference viewed: 11 (1 ULg)
Full Text
Peer Reviewed
See detailSampling methods for amphipods of Posidonia oceanica meadows: a comparative study
Michel, Loïc ULg; Lepoint, Gilles ULg; Dauby, Patrick ULg et al

in Crustaceana (2010), 83(1), 39-47

Efficient sampling of amphipod crustaceans associated with Posidonia oceanica (L.) Delile meadows is difficult, due to their complex community structure and to the heterogeneity of the meadows. Here we ... [more ▼]

Efficient sampling of amphipod crustaceans associated with Posidonia oceanica (L.) Delile meadows is difficult, due to their complex community structure and to the heterogeneity of the meadows. Here we compare three sampling techniques: the hand-towed net, the air-lift, and light traps. Each of the methods shows specific advantages and disadvantages, hence the most important feature to consider in the choice of the method would be its adequacy with regard to the study purpose. Moreover, the most accurate way to sample amphipods from P. oceanica meadows could be to combine several methods, keeping in mind their respective strengths and weaknesses, and to adapt the sampling protocol to the aims of the study at issue. [less ▲]

Detailed reference viewed: 128 (20 ULg)
Full Text
Peer Reviewed
See detailBulk organic geochemistry of sediments from Puyehue Lake and its watershed (Chile, 40°S): Implications for paleoenvironmental reconstructions
Bertrand, Sébastien; Sterken, Mieke; Vargas-Ramirez, Lourdes et al

in Palaeogeography, Palaeoclimatology, Palaeoecology (2010), 294

Since the last deglaciation, the mid-latitudes of the southern Hemisphere have undergone considerable environmental changes. In order to better understand the response of continental ecosystems to ... [more ▼]

Since the last deglaciation, the mid-latitudes of the southern Hemisphere have undergone considerable environmental changes. In order to better understand the response of continental ecosystems to paleoclimate changes in southern South America, we investigated the sedimentary record of Puyehue Lake, located in the western piedmont of the Andes in South-Central Chile (40°S). We analyzed the elemental (C, N) and stable isotopic ([delta]13C, [delta]15N) composition of the sedimentary organic matter preserved in the lake and its watershed to estimate the relative changes in the sources of sedimentary organic carbon through space and time. The geochemical signature of the aquatic and terrestrial end-members was determined on samples of lake particulate organic matter (N/C: 0.130) and Holocene paleosols (N/C: 0.069), respectively. A simple mixing equation based on the N/C ratio of these end-members was then used to estimate the fraction of terrestrial carbon ([latin small letter f with hook]T) preserved in the lake sediments. Our approach was validated using surface sediment samples, which show a strong relation between [latin small letter f with hook]T and distance to the main rivers and to the shore. We further applied this equation to an 11.22 m long sediment core to reconstruct paleoenvironmental changes in Puyehue Lake and its watershed during the last 17.9 kyr. Our data provide evidence for a first warming pulse at 17.3 cal kyr BP, which triggered a rapid increase in lake diatom productivity, lagging the start of a similar increase in sea surface temperature (SST) off Chile by 1500 years. This delay is best explained by the presence of a large glacier in the lake watershed, which delayed the response time of the terrestrial proxies and limited the concomitant expansion of the vegetation in the lake watershed (low [latin small letter f with hook]T). A second warming pulse at 12.8 cal kyr BP is inferred from an increase in lake productivity and a major expansion of the vegetation in the lake watershed, demonstrating that the Puyehue glacier had considerably retreated from the watershed. This second warming pulse is synchronous with a 2 °C increase in SST off the coast of Chile, and its timing corresponds to the beginning of the Younger Dryas Chronozone. These results contribute to the mounting evidence that the climate in the mid-latitudes of the southern Hemisphere was warming during the Younger Dryas Chronozone, in agreement with the bipolar see-saw hypothesis. [less ▲]

Detailed reference viewed: 83 (15 ULg)
Full Text
See detailA 500-yr record of Northern Patagonian environmental changes: Lago Plomo and Lago Bertrand
Fagel, Nathalie ULg; Brix, J.; El Ouahabi, M. et al

Poster (2010)

Detailed reference viewed: 24 (4 ULg)
Full Text
Peer Reviewed
See detailGeochemical evidence (C, N and Pb isotopes) of recent anthropogenic impact in south-central Chile from two environmentally distinct lake sediment records
Fagel, Nathalie ULg; Bertrand, Sebastien; Mattielli, Nadine et al

in Journal of Quaternary Science (2010), 25(7), 1100-1112

In this paper, we compare the elemental and isotopic (C, N, Pb) geochemistry of lake sediments from two contrasted environments in south-central Chile. The first lake, Laguna Chica de San Pedro (LCSP), is ... [more ▼]

In this paper, we compare the elemental and isotopic (C, N, Pb) geochemistry of lake sediments from two contrasted environments in south-central Chile. The first lake, Laguna Chica de San Pedro (LCSP), is situated in the urbanised area of the Biobio Region (36°S). The second lake, Lago Puyehue (40° S), is located 400 km to the southeast of LCSP and within an Andean national park. Our aim is to identify environmental impacts associated with increasing industrial activities and land degradation during the last 150 a. In LCSP, shifts in C/N atomic ratios, 13C and 15N from 1915-1937 to the late 1980s are attributed to successive land degradation episodes in the lake watershed. Based on a Pb isotopic mixing model, we estimate that up to 20% of lead in LCSP sediments is supplied from urban atmospheric pollution. By contrast, human impact in the watershed of Lago Puyehue is very limited. We observe no change in organic geochemistry during the last 150 a and lead contamination remains lower than 5%, even during the last decades. Although contamination levels are much higher in LCSP than in Lago Puyehue, a peak in anthropogenic Pb is recorded during the same period (1974-1976) at both sites. This maximum contamination level is consistent with increased industrial activity in the vicinity of Concepción. [less ▲]

Detailed reference viewed: 63 (9 ULg)
Full Text
Peer Reviewed
See detailTracing sewage and natural freshwater input in a Northwest Mediterranean bay: Evidence obtained from isotopic ratios in marine organisms
Lassauque, Julien; Lepoint, Gilles ULg; Thibaut, T. et al

in Marine Pollution Bulletin (2010), 60(6), 843-851

Elemental carbon and nitrogen levels and isotope ratios were assessed in different biological compartments of a Northwest (NW) Mediterranean bay to trace the various sources of nutrient input from natural ... [more ▼]

Elemental carbon and nitrogen levels and isotope ratios were assessed in different biological compartments of a Northwest (NW) Mediterranean bay to trace the various sources of nutrient input from natural (river runoffs) and anthropogenic (harbor outflows, fish farms and urban sewage outfall) sources. Samples from transplanted mussels and natural sea grass communities (Posidonia oceanica leaves and epiphytes) were harvested from different locations throughout the bay during the touristic summer and rainy seasons. The results from the nitrogen analysis revealed that sewage and harbor outflow promote higher nitrogen levels, enrichment of N-15 in the tissues, and a higher seasonal variability in sea grass and epiphytes. In mussel tissues, the delta N-15 was also influenced by sewage and harbor outflow, whereas delta C-13 was influenced by terrestrial inputs. These results suggest that natural and anthropogenic nutrient inputs have a temporary and localized influence and affect the sensitivity of natural isotopic ratios to changes in hydrologic conditions, especially to rain and tourism. (C) 2010 Elsevier Ltd. All rights reserved. [less ▲]

Detailed reference viewed: 60 (3 ULg)
Full Text
See detailMultidisciplinary study of the trophic diversity and functional role of amphipod crustaceans associated to Posidonia oceanica meadows
Michel, Loïc ULg; Lepoint, Gilles ULg; Gobert, Sylvie ULg et al

Poster (2009, November 27)

Posidonia oceanica is a seagrass endemic to the Mediterranean Sea, and is able to form large monospecific areas, called meadows. These meadows are critical features of the Mediterranean coastal zones, and ... [more ▼]

Posidonia oceanica is a seagrass endemic to the Mediterranean Sea, and is able to form large monospecific areas, called meadows. These meadows are critical features of the Mediterranean coastal zones, and are of great ecologic and economic importance. Posidonia oceanica meadows shelter high biomasses and biodiversities of amphipod crustaceans. In other temperate meadows, such as Atlantic Zostera marina 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, due to the lack of precise studies, and little is known about the trophic ecology of amphipods. In this context, our research is structured in three main tasks. We chose the Calvi Bay (NW Corsica, France) as a study site, and sampling is undertaken from the STARESO research station (University of Liège, Belgium). First, we study the exact composition of the amphipod community, as well as its temporal variation at diel and seasonal scale. This task is based on in situ collection of samples using three methods: the hand-towed net, litter collection and light traps. Completion of this task will allow us to have accurate and reliable data, taken on our study site, concerning the abundance and specific diversity of amphipods associated with P. oceanica meadows. The second task is a reconstruction of the diet of the studied animals. Indeed, amphipods from P. oceanica meadows are usually regarded as vegetal epiphytes grazers, or generalist detritivores, but few studies focus on the interspecific trophy diversity, or on the importance of alternative food sources. Our approach relies on in situ sampling of amphipods and potential food items. The techniques used combine traditional methods (gut content observation) and use of trophic markers, such as measurements of C and N stable isotope rations and fatty acid composition analysis. Finally, we use in vitro and in situ microcosms experiments to evaluate the impact of amphipod feeding activity on the ecosystem functioning, and more precisely on the dynamics of the epiphyte cover. By quantifying this interaction, our purpose is to put back the results obtained in the first two parts into a wider context, the functioning of the Posidonia oceanica meadow as an ecosystem. Thus, by combining in situ sampling and in vitro experimentation, and by combining traditional and innovating techniques, we hope, at the end of this research, to enhance the knowledge of the trophic diversity and the functional role of amphipod crustaceans associated with Mediterranean Posidonia meadows. [less ▲]

Detailed reference viewed: 82 (28 ULg)
Full Text
See detailUse of C & N stable isotopes to evaluate interspecific trophic diversity among amphipods from Posidonia oceanica meadows
Michel, Loïc ULg; Lepoint, Gilles ULg; Nyssen, Fabienne ULg et al

Poster (2009, January 27)

Amphipods are one of the most diverse and abundant taxa of vagile invertebrates associated to Mediterranean Posidonia oceanica meadows. Therefore, they likely play an essential part in those ecosystems’ ... [more ▼]

Amphipods are one of the most diverse and abundant taxa of vagile invertebrates associated to Mediterranean Posidonia oceanica meadows. Therefore, they likely play an essential part in those ecosystems’ functioning, notably in organic matter transfers from producers to higher level consumers. Nevertheless, their trophic ecology remains poorly known, and they are generally regarded as epiflora grazers or generalist detritivores. Here, we focused on interspecific trophic diversity, and on the importance of other food sources (epifauna, Posidonia leaves & litter, suspended organic matter, …) in those amphipod’s diet. To achieve these goals, we used C and N stable isotopes ratios as trophic tracers. We noticed considerable trophic diversity among amphipods from different species, with δ13C values ranging from -16 to -26 ‰. Moreover, while some species (such as Apherusa chiereghinii and Aora spinicornis) seem to feed mainly on epiphytes, others, like Dexamine spiniventris, exploit other food sources. This study enhances the comprehension of the feeding ecology of these amphipods, and therefore of the way they interact with the Posidonia meadow ecosystem. [less ▲]

Detailed reference viewed: 80 (30 ULg)
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)

Detailed reference viewed: 8 (0 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 107 (26 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 181 (15 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 82 (15 ULg)
Full Text
Peer Reviewed
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 ▲]

Detailed reference viewed: 96 (3 ULg)