References of "Gobert, Sylvie"
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See detailLa Posidonie, Cap Sur
Réseau Mer; Gobert, Sylvie ULg

Learning material (2007)

La posidonie sous le regard du scientifique, du gestionnaire, du plongeur, de l'historien, de l'élu du littoral, du plaisancier, du pêcheur, du baigneur et du juriste.

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See detailLong-Term Feeding Ecology and Habitat Use in Harbour Porpoises Phocoena Phocoena from Scandinavian Waters Inferred from Trace Elements and Stable Isotopes
Fontaine, Michael ULg; Tolley, K. A.; Siebert, U. et al

in BMC Ecology (2007), 7

BACKGROUND: We investigated the feeding ecology and habitat use of 32 harbour porpoises by-caught in 4 localities along the Scandinavian coast from the North Sea to the Barents Sea using time-integrative ... [more ▼]

BACKGROUND: We investigated the feeding ecology and habitat use of 32 harbour porpoises by-caught in 4 localities along the Scandinavian coast from the North Sea to the Barents Sea using time-integrative markers: stable isotopes (delta13C, delta15N) and trace elements (Zn, Cu, Fe, Se, total Hg and Cd), in relation to habitat characteristics (bathymetry) and geographic position (latitude). RESULTS: Among the trace elements analysed, only Cd, with an oceanic specific food origin, was found to be useful as an ecological tracer. All other trace elements studied were not useful, most likely because of physiological regulation and/or few specific sources in the food web. The delta13C, delta15N signatures and Cd levels were highly correlated with each other, as well as with local bathymetry and geographic position (latitude). Variation in the isotopic ratios indicated a shift in harbour porpoise's feeding habits from pelagic prey species in deep northern waters to more coastal and/or demersal prey in the relatively shallow North Sea and Skagerrak waters. This result is consistent with stomach content analyses found in the literature. This shift was associated with a northward Cd-enrichment which provides further support to the Cd 'anomaly' previously reported in polar waters and suggests that porpoises in deep northern waters include Cd-contaminated prey in their diet, such as oceanic cephalopods. CONCLUSION: As stable isotopes and Cd provide information in the medium and the long term respectively, the spatial variation found, shows that harbour porpoises experience different ecological regimes during the year along the Scandinavian coasts, adapting their feeding habits to local oceanographic conditions, without performing extensive migration. [less ▲]

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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 detailTrophic diversity and potential role of detritivorous crustaceans in Posidonia oceanica litter
Sturaro, Nicolas ULg; Gobert, Sylvie ULg; Cox, Anne-Sophie et al

Conference (2006, June)

Detrivorous crustaceans are pivotal components of the trophic food webs and are found to be the main constituents of the macrofauna in Posidonia oceanica litter. The coexistence of many of these species ... [more ▼]

Detrivorous crustaceans are pivotal components of the trophic food webs and are found to be the main constituents of the macrofauna in Posidonia oceanica litter. The coexistence of many of these species in the same biotope raises the question of trophic diversity and of its role in litter degradation process. Diet composition of five common species of detrivorous crustaceans in P. oceanica litter (i.e. the gammarid amphipods Gammarella fusicola and Gammarus aequicauda and the isopods Idotea baltica, Idotea hectica and Zenobiana prismatica) were studied using a combination of gut content and stable isotopes analysis. Despite the common food supply (i.e. Posidonia dead leaf, Posidonia epiphytes or drift macroalgae), there were considerable interspecific differences in diet composition. Gut content observations indicate that P. oceanica leaf litter is an important part of the ingested food of all the species. Algae material (macroepiphytes and drift macroalgae) inhabiting the litter is mainly found in G. fusicola, I. hectica and I. baltica. I. baltica displays a high proportion of crustacean fragments. Isotope ratios showed that most of the species do not assimilate much of the ingested Posidonia. Application of a mixing model using isotopic values to estimate the contribution of the potential different food sources confirms this view. On one hand, the tissue of G. aequicauda could be constituted by more than 50 % of P. oceanica carbon. On the other hand, for the other species studied, P. oceanica represented a minor contribution (10 - 30 %), although it is a major component of the gut contents. This could imply that micro-organism (diatoms, bacteria and fungi) living on the Posidonia detritus is a major food source of detrivorous. Moreover, I. baltica, Z. prismatica and G. fusicola have a diversified diet composed mainly of algae. Crustaceans are an important food source for I. baltica. By contrast, I. hectica indicated a major contribution of algae material. Our results demonstrate the trophic diversity existing between the detrivorous crustaceans species in P. oceanica litter. This trophic diversity is probably one of the factors that allows these species to coexist in the same biotope. The results also underline the potential role of these species in the degradation of P. oceanica litter by fragmenting mechanically the Posidonia detritus and by assimilating directly Posidonia carbon and transferring it to higher trophic level (i.e. coastal fishes). Moreover, it allows us to think that micro-organisms (diatoms, bacteria and fungi) colonising leaf litter may constitute an important food source for litter fauna. [less ▲]

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See detailUse of Posidonia oceanica sheaths as a biomonitor of metal pollution.
Gosselin, Marc; Bouquegneau, Jean-Marie ULg; Pergent, Gérard et al

in Biologia Marina Mediterranea (2006), 13

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See detailIn situ sampling of pore waters from seagrass meadows
Gobert, Sylvie ULg; Lepoint, Gilles ULg; Biondo, Renzo ULg et al

in Biologia Marina Mediterranea (2006), 13

A routine and low cost method to collect pore water in a seagrass meadow in situ and underwater is here proposed. The method consists of direct-suction filtered sampling allowing the determination of ... [more ▼]

A routine and low cost method to collect pore water in a seagrass meadow in situ and underwater is here proposed. The method consists of direct-suction filtered sampling allowing the determination of nutrient concentrations in the sampled water. Data ranges of nutrient (NO2-+NO3-; HPO4 2- and NH4+) concentrations in a P. oceanica meadow are also discussed [less ▲]

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See detailTrace Metal Concentrations in Posidonia Oceanica of North Corsica (Northwestern Mediterranean Sea): Use as a Biological Monitor?
Gosselin, Marc; Bouquegneau, Jean-Marie ULg; Lefèbvre, Frédéric et al

in BMC Ecology (2006), 6

BACKGROUND: Within semi-closed areas like the Mediterranean Sea, anthropic wastes tend to concentrate in the environment. Metals, in particular, are known to persist in the environment and can affect ... [more ▼]

BACKGROUND: Within semi-closed areas like the Mediterranean Sea, anthropic wastes tend to concentrate in the environment. Metals, in particular, are known to persist in the environment and can affect human health due to accumulation in the food chain. The seagrass Posidonia oceanica, widely found in Mediterranean coastal waters, has been chosen as a "sentinel" to quantify the distribution of such pollutants within the marine environment. Using a technique similar to dendrochronology in trees, it can act as an indicator of pollutant levels over a timeframe of several months to years. In the present study, we measured and compared the levels of eight trace metals (Cr, Ni, Cu, Zn, As, Se, Cd, and Pb) in sheaths dated by lepidochronology and in leaves of shoots sampled from P. oceanica meadows collected from six offshore sites in northern Corsica between 1988 and 2004; in the aim to determine 1) the spatial and 2) temporal variations of these metals in these areas and 3) to compared these two types of tissues. RESULTS: We found low trace metal concentrations with no increase over the last decade, confirming the potential use of Corsican seagrass beds as reference sites for the Mediterranean Sea. Temporal trends of trace metal concentrations in sheaths were not significant for Cr, Ni, Cu, As or Se, but Zn, Cd, and Pb levels decreased, probably due to the reduced anthropic use of these metals. Similar temporal trends between Cu levels in leaves (living tissue) and in sheaths (dead tissue) demonstrated that lepidochronology linked with Cu monitoring is effective for surveying the temporal variability of this metal. CONCLUSION: Leaves of P. oceanica can give an indication of the metal concentration in the environment over a short time period (months) with good accuracy. On the contrary, sheaths, which gave an indication of changes over long time periods (decades), seem to be less sensitive to variations in the metal concentration in the environment. Changes in human consumption of metals (e.g., the reduction of Pb in fuel) are clearly reflected in both organs. These results confirm that P. oceanica is a good bioindicator of metals and a good biomonitor species for assessing Cu in the environment. [less ▲]

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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 detailDescriptors of Posidonia oceanica meadows: Use and application
Pergent-Martini, Christine; Leoni, Vanina; Pasqualini, Vanina et al

in Ecological Indicators (2005), 5(3), 213-230

The conservation of the coastal marine environment requires the possession of information that enables the global quality of the environment to be evaluated reliably and relatively quickly. The use of ... [more ▼]

The conservation of the coastal marine environment requires the possession of information that enables the global quality of the environment to be evaluated reliably and relatively quickly. The use of biological indicators is often an appropriate method. Seagrasses in general, and Posidonia oceanica meadows in particular, are considered to be appropriate for biomonitoring because of their wide distribution, reasonable size, sedentary habit, easy collection and abundance and sensitivity to modifications of littoral zone. Reasoned management, on the scale of the whole Mediterranean basin, requires standardized methods of study, to be applied by both researchers and administrators, enabling comparable results to be obtained. This paper synthesises the existing methods applied to monitor P. oceanica meadows, identifies the most suitable techniques and suggests future research directions. From the results of a questionnaire, distributed to all the identified laboratories working on this topic, a list of the most commonly used descriptors was drawn up, together with the related research techniques (e.g. standardization, interest and limits, valuation of the results). It seems that the techniques used to study meadows are rather similar, but rarely identical, even though the various teams often refer to previously published works. This paper shows the interest of a practical guide that describes, in a standardized way, the most useful techniques enabling P. oceanica meadows to be used as an environmental descriptor. Indeed, it constitutes the first stage in the process. (c) 2005 Elsevier Ltd. All rights reserved. [less ▲]

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See detailRestoration of Posidonia oceanica meadows : means and limitations.
Gobert, Sylvie ULg; Lepoint, Gilles ULg; Bouquegneau, Jean-Marie ULg et al

in Proceedings of the seventh international conference on the Mediterranean coastal environment. Medcoast 05 (2005)

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See detailC, N, P concentrations and requirements of flowering Posidonia oceanica shoots
Gobert, Sylvie ULg; Lejeune, Pierre; Lepoint, Gilles ULg et al

in Hydrobiologia (2005), 533

The carbon, nitrogen and phosphorus contents in flowering and nonflowering shoots were compared after an important flowering event occurred in the Posidonia meadow of the Bay of Calvi. The flower ... [more ▼]

The carbon, nitrogen and phosphorus contents in flowering and nonflowering shoots were compared after an important flowering event occurred in the Posidonia meadow of the Bay of Calvi. The flower formation caused a significant increase of C and a significant decrease of N concentrations in intermediate and adult leaves. Minimum daily requirements in mg shoot(-1) day(-1) of 3.4 and 4.8 of C, 0.09 and 0.09 N, 0.01 and 0.02 of P respectively for nonflowering and flowering shoots were calculated. It shows that additional quantities of C and P are required for the inflorescence elaboration. The unchanged quantity of N required by the shoot for the inflorescence elaboration and the significant modification of N concentration in intermediate and adult leaves suggests that N is limited in the environment and that an efficient resorption of N occurs from leaves to ensure the inflorescence formation. [less ▲]

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See detailRecommandations pour un programme de surveillance adapté aux objectifs de la DCE (recommandations concernat le benthos marins)
Guillaumont; Gauthier, E.; Gobert, Sylvie ULg

Report (2005)

L'application de la DCE nécessite la mise en place de contrôles pour évaluer l'état écologique des Masses d'eau côtières.

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See detailEffect of transplantation on Posidonia oceanica shoots
Vangeluwe, Denis; Lepoint, Gilles ULg; Bouquegneau, Jean-Marie ULg et al

in Vie et Milieu-Life and Environment (2004), 54(4), 223-230

Posidonia oceanica shoots sampled from the healthy meadow in the bay of Revelatta (Corsica, France) were transplanted on metallic grids at 10 m depth. Transplanted shoots have been regularly monitored by ... [more ▼]

Posidonia oceanica shoots sampled from the healthy meadow in the bay of Revelatta (Corsica, France) were transplanted on metallic grids at 10 m depth. Transplanted shoots have been regularly monitored by the measurement of growth, biomass and C, N and P contents in the leaves and the belowground parts. After six months of experiment, the survival rates varied from 14 to 84 % on the different transplantation sites. Leaf biomass on the transplanted cuttings was lower than biomass in the control shoots but root biomass raised from December 2000 to May 2001 on the transplanted shoots. Transplant growth (8,3 +/- 2,3 mm.d(-1).shoot(-1)) after six months was similar to control growth (8,2 +/- 2,8 mm.d(-1). shoot(-1)). The C, N and P contents in transplants were significatively lower than in control shoots suggesting that transplanted cuttings are unable to meet their nutrient requirements. The modifications of the C, N, P contents in the belowground parts of the transplanted shoots indicate a mobilization of these nutrients in those compartments to produce new roots and restore a normal nutrients absorption. [less ▲]

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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 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 detailNitrogen dynamics in Posidonia oceanica cuttings: implications for transplantation experiments
Lepoint, Gilles ULg; Vangeluwe, Denis; Eisinger, Michael et al

in Marine Pollution Bulletin (2004), 48(5-6), 465-470

A N-15 tracer study was performed during an experimental transplantation trial of natural Posidonia oceanica cuttings. The experiment was done in situ at 17 m depth in the Revellata Bay (Calvi, NW Corsica ... [more ▼]

A N-15 tracer study was performed during an experimental transplantation trial of natural Posidonia oceanica cuttings. The experiment was done in situ at 17 m depth in the Revellata Bay (Calvi, NW Corsica, France). Despite high survival rates of transplants (>90%) after one year, the weight and the N content of transplants are significantly lower than those of reference plants. In absence of roots, the transplants are not able to meet their N requirement because, leaf uptake is insufficient to replenish the N lost during the natural leaf decay. This could constitute a major cause of long-term failure for transplantation experiments or natural recolonisation processes. The increase of the N-15 content in the roots shows that the plant re-allocates the nitrogen of one organ (i.e. leaves, rhizomes) to ensure the growth of another (i.e. roots). (C) 2003 Elsevier Ltd. All rights reserved. [less ▲]

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