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See detailBiodiversity of three representative groups of the Antarctic zoobenthos - Coping with change (BIANZO II)
Raes, Maarten; Vanreusel, Ann; Pasotti, Francesca et al

Report (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 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 detailDifferential isotopic turnover (C and N) detected in Antarctic scavenger amphipods
Nyssen, Fabienne ULg; Michel, Loïc ULg; Dauby, Patrick ULg et al

Poster (2008, August)

Metabolic activity is positively related to temperature, inversely to body mass and is a function of taxon specific life style features, in particular activity such as level of active movement. Therefore ... [more ▼]

Metabolic activity is positively related to temperature, inversely to body mass and is a function of taxon specific life style features, in particular activity such as level of active movement. Therefore, the isotope signal transfer velocity is expected to be lower in cold environments and in larger as well as less active organisms. Our study explores whether this may be a problem in trophic studies of a comparatively “slow” because cold system such as the high Antarctic shelf ecosystem and in comparatively large organisms such as benthic amphipod species within this system. We compare experimentally the velocity of stable isotope signal transfer from prey to consumer in three lysianassoid amphipods, Waldeckia obesa, Abyssorchomene plebs and Pseudorchomene coatsi. They have similar alimentation, but different size and lifestyle. Indeed, W. obesa is a very sedentary species spending most of the time immobilized on diverse substrates whereas P. coatsi is very motile, swimming rapidly around the aquarium. The third species, A. plebs has an intermediate behaviour, sharing time between short swim and resting on bottom. Those species also differ significantly in size: and are good representative of scavenger trophic guild on Antarctic shelf. After being starved, amphipods were kept by species and fed ad libitum with lyophilized fish during fifty days. Individuals were sacrificed weekly for isotopic analysis. At the end of the 7-week incubation with standardized food, rank correlation of δ13C and δ15N against time did not show any consistent trend for A. plebs (δ13C: p = 0.51 and δ15N p = 0.04) neither for the species W. obesa (δ13C: p = 0.77 and δ15N p = 0.26). By contrast, for P. coatsi, rank correlations were highly significant (p < 0.0001). The linear regression illustrated a clear increase of isotopic ratios all along the experiment. This metabolic discrepancy between species is probably a size-mass effect. Furthermore, for this species, ANCOVA of the individually measured isotopic ratios first transformed to an offset value (rate vs carbon ↔ nitrogen, covariate time) provided evidence for significant effects of the parameter “isotope” on isotopic temporal evolution. Indeed, the δ13C values evolve much faster than the δ15N ones. According to data, it would take double time for P. coatsi to balance its nitrogen isotopic signature than its carbon isotopic ratio when changing food. Those results are critically discussed. [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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See detailSCAR-MarBIN, the Antarctic marine biodiversity information network.
Danis, Bruno; et al.; Dauby, Patrick ULg et al

Poster (2007, April 12)

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See detailBIANZO: biodiversity of three representative groups of the Antarctic Zoobenthos: comparative structure, distribution and fucntion
De Broyer, Claude; Vanreusel, Ann; Vanhove, Sandra et al

Report (2007)

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See detailFood sources of two detritivore amphipods associated with the seagrass Posidonia oceanica leaf litter
Lepoint, Gilles ULg; Cox, Anne-Sophie; Dauby, Patrick ULg et al

in Marine Biology Research (2006), 2(5), 355-365

This study focused on the ingestion and assimilation of Posidonia oceanica (L.) Delile litter by Gammarella fucicola Leach and Gammarus aequicauda Martynov, two dominant detritivore amphipods of the P ... [more ▼]

This study focused on the ingestion and assimilation of Posidonia oceanica (L.) Delile litter by Gammarella fucicola Leach and Gammarus aequicauda Martynov, two dominant detritivore amphipods of the P. oceanica leaf litter. Scanning electron microscope observations indicated that leaf litter is highly colonized by diverse diatoms, bacteria and fungi, which may constitute a potential food source for the litter fauna. Gut content observations demonstrated that these species eat P. oceanica litter, and that this item is an important part of their ingested diet. Stable isotope analyses showed that the species do not experience the same gains from the ingested Posidonia. Gammarella fucicola displayed isotopic values, suggesting a major contribution of algal material (micro- and macro-epiphytes or drift macro-algae). On the other hand, the observed isotopic values of G. aequicauda indicated a more important contribution of P. oceanica carbon. The mixing model used agreed with this view, with a mean contribution of P. oceanica to approximately 50% (range 40-55%) of the assimilated biomass of G. aequicauda. This demonstrated that the two species, suspected to be detritus feeders, display in reality relatively different diets, showing that a certain degree of trophic diversity may exist among the detritivore community of the seagrass litter. [less ▲]

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See detailBIANZO, BIodiversity of ANtarctic ZOobenthos.
De Broyer, Claude; Vanreusel, Ann; De Ridder, Chantal et al

Poster (2006, March)

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See detailBiology of Posidonia
Gobert, Sylvie ULg; Cambridge, M. L.; Velimirov et al

in Larkum, Anthony WD; Orth, Robert J; Duarte, Carlos M (Eds.) Seagrasses: Biology, Ecology and Conservation (2006)

The aim of this chapter is to place emphasis on the dynamics of Posidonia systems in order to detect key ecosystem processes and to put in evidence the large differences between the Mediterranean and ... [more ▼]

The aim of this chapter is to place emphasis on the dynamics of Posidonia systems in order to detect key ecosystem processes and to put in evidence the large differences between the Mediterranean and Australian systems. These key processes shall be the basis to formulate new working hypothesis in order to verify newly emerging concepts and propose management plans in order to ensure the sustainability of the system. [less ▲]

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See detailScavenger amphipod crustaceans from Antarctic deep-sea: composition, distribution and ecofunctional role.
De Broyer, Claude; Nyssen, Fabienne; Dauby, Patrick ULg

Poster (2005, July)

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See detailDeûs meûs al rikwîre dès p'titès bièsses nin k'nohowes d'vin lès baheûrs abôminabes dè Pole Sûd
Dauby, Patrick ULg

Conference given outside the academic context (2005)

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See detailApplications of C and N stable isotopes to ecological and environmental studies in seagrass ecosystems
Lepoint, Gilles ULg; Dauby, Patrick ULg; Gobert, Sylvie ULg

in Marine Pollution Bulletin (2004), 49(11-12), 887-891

Stable isotopes of carbon and nitrogen are increasingly used in marine ecosystems, for ecological and environmental studies. Here, we examine some applications of stable isotopes as ecological integrators ... [more ▼]

Stable isotopes of carbon and nitrogen are increasingly used in marine ecosystems, for ecological and environmental studies. Here, we examine some applications of stable isotopes as ecological integrators or tracers in seagrass ecosystem studies. We focus on both the use of natural isotope abundance as food web integrators or environmental tracers and on the use of stable isotopes as experimental tools. As ecosystem integrators, stable isotopes have helped to elucidate the general structure of trophic webs in temperate, Mediterranean and tropical seagrass ecosystems. As environmental tracers, stable isotopes have proven their utility in sewage impact measuring and mapping. However, to make such environmental studies more comprehensible, future works on understanding of basic reasons for variations of N and C stable isotopes in seagrasses should be encouraged. At least, as experimental tracers, stable isotopes allow the study of many aspects of N and C cycles at the scale of a plant or at the scale of the seagrass ecosystem. (C) 2004 Elsevier Ltd. All rights reserved. [less ▲]

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See detailToxards a SCAR Marine Biodiversity Information Network (SCAR MarBIN)
De Broyer, Claude; Danis, Bruno; Meerhaege, Angelo et al

Poster (2004, September)

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See detailTowards a SCAR 'Marine Biodiversity Information Network'
De Broyer, Claude; Danis, Bruno; Meerhaeghe, A et al

Poster (2004, July)

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See detailCombination of trophic biomarkers to distinguish among Antarctic amphipods trophic guilds
Nyssen, Fabienne ULg; Dauby, Patrick ULg; Graeve, Martin

Conference (2004, July)

Peracarid crustaceans and amphipods in particular are an important group in the Southern Ocean and one of the most diverse in the macrozoobenthos. As a part of a multidisciplinary study of the amphipods ... [more ▼]

Peracarid crustaceans and amphipods in particular are an important group in the Southern Ocean and one of the most diverse in the macrozoobenthos. As a part of a multidisciplinary study of the amphipods ecological roles in Antarctic benthic systems, about 150 specimens belonging to 25 species of 10 of the most common amphipod families occurring in the Southern Ocean have been involved in this study of amphipod trophic patterns. Beside “classical” stomach content analysis or field observations, the use of naturally occurring stable isotopes of carbon (δ13C) and nitrogen (δ15N) has recently provided new insights into food web ecology. This method is based on the direct relationship established between the isotopic signature of an organism and that of its preys. Nitrogen-15 typically shows a step-wise increase with trophic level within a food chain. Closer to the value of the diet, carbon-13 is preferentially used to assess the relative proportion of potential primary sources in a trophic web (ex.: pelagic vs benthic contribution to food intake). Furthermore, for several species, the lipid signature – which has already been used successfully to help understand marine trophodynamics – and more particularly the fatty acid composition has been investigated as trophic biomarkers to reveal more precisely to which trophic guild they belong to. [less ▲]

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See detailContributions of benthic and planktonic primary producers to nitrate and ammonium uptake fluxes in a nutrient-poor shallow coastal area (Corsica, NW Mediterranean)
Lepoint, Gilles ULg; Gobert, Sylvie ULg; Dauby, Patrick ULg et al

in Journal of Experimental Marine Biology and Ecology (2004), 302(1), 107-122

By using the stable isotope N-15, we have measured in situ the uptake of nitrate and ammonium by the seagrass Posidonia oceanica, its leaf epiphyte community, the brown macroalgae Halopteris scoparia and ... [more ▼]

By using the stable isotope N-15, we have measured in situ the uptake of nitrate and ammonium by the seagrass Posidonia oceanica, its leaf epiphyte community, the brown macroalgae Halopteris scoparia and the suspended particulate organic matter (SPOM). In Revellata Bay (Gulf of Calvi, Westem Corsica), which is a very nutrient-poor region, the specific uptake rates (V) (mug N g N 1 h(- 1)) of SPOM measured at ambient concentrations are 10-1000 higher than those of benthic primary producers. Macroalgae have intermediary v, between the seagrass leaf and leaf epiphytes. V are quite variable and the reasons for this variability remain unclear. Despite the difference of specific uptake rates found between benthic and pelagic primary producers, when integrating the uptake fluxes for a water Column of 10 m depth, the contribution of benthic primary producers to N uptake fluxes (g N m(-) (2) h(-) (1)) is significant, corresponding on average to 40% of total uptake flux. This results from the dominance in terms of N biomass of benthic primary producers in this shallow nutrient-poor area. When reported for the entire volume of the Revellata Bay, the contribution of benthic primary producers is reduced to 5 - 10% of total N uptake flux. Although this contribution could appear relatively low, it results in a significant direct transfer of inorganic nitrogen from the water column to the benthic compartment. By this transfer, the benthic plants act as a biological pump incorporating the pelagic N into the benthic compartment for a time longer than the characteristic time of phytoplankton dynamics (month-years vs. day-week). (C) 2003 Elsevier B.V. Alt rights reserved. [less ▲]

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See detailThe crustacean scavenger guild in Antarctic shelf, bathyal and abyssal communities
De Broyer, Claude; Nyssen, Fabienne ULg; Dauby, Patrick ULg

in Deep-Sea Research Part II, Topical Studies in Oceanography (2004), 51(14-16), 1733-1752

Peracarid crustaceans form a significant part of the macrobenthic community that is responsible for scavenging on large food falls onto the sea floor. Although several studies are available about ... [more ▼]

Peracarid crustaceans form a significant part of the macrobenthic community that is responsible for scavenging on large food falls onto the sea floor. Although several studies are available about scavengers from tropical and temperate seas, very little information has been published about such species living in Antarctic waters, particularly at greater depths. The present paper is based on a collection of 31 baited trap sets deployed in the Weddell Sea, Scotia Sea, and off the South Shetland Islands, and presents results on the geographical and bathymetric distribution of the different taxa and on the eco-functional role of scavengers. <br /> <br />Some 68,000 peracarid crustaceans from 62 species were collected. About 98% of individuals belonged to the amphipod superfamily Lysianassoidea, and 2% to the isopod family Cirolanidae. Of these species, 31, including 26 lysianassoids (1400 individuals), were collected deeper than 1000 m. <br /> <br />High species richness was discerned for the eastern Weddell Sea shelf compared with other Antarctic areas. The Antarctic slope also seems to be richer in species than other areas investigated in the world, while in the abyss, scavenger species richness appears to be lower in Antarctica. A richness gradient was thus observed from the shelf to the deep. For amphipods, a number of species extend their distribution from the shelf to the slope and only one to the abyssal zone. <br /> <br />Amphipod species showed degrees of adaptation to necrophagy. The functional adaptations of the mandible and the storage function of the gut are discussed. Feeding experiments conducted on lysianassoid species collected at great depths and maintained in aquaria showed a mean feeding rate of about 1.4–4.1% dry body weight day−1, which is consistent with data obtained from other species. [less ▲]

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