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See detailOrganisms as ecosystems engineers: the case of amphipod grazers from Posidonia oceanica meadows
Michel, Loïc ULg; Schnitzler, Joseph ULg; Dupont, Alessandra et al

Poster (2011, February 25)

Posidonia oceanica is a seagrass endemic to the Mediterranean Sea, and is able to form large monospecific areas, called meadows. These meadows shelter high biomasses and biodiversities of amphipod ... [more ▼]

Posidonia oceanica is a seagrass endemic to the Mediterranean Sea, and is able to form large monospecific areas, called meadows. These meadows shelter high biomasses and biodiversities of amphipod crustaceans. Moreover, It is now established that several species of these amphipods feed on the macro-epiphytes present on the leaves of the seagrass. Here, we performed in situ experiments to assess whether this grazing activity could impact the dynamics of the leaves’ epiphytic cover, and thus influence the functioning of the meadow as an ecosystem. We used microcosms containing monospecific populations of 3 amphipods taxa (Apherusa chiereghinii, Dexamine spiniventris and Gammarus spp.), and placed them directly in the meadow, at a depth of 10m. Biomasses of erected macroalgae and erected animals (hydrozoans, bryozoans) were lower in all grazed treatments. However, none of the studied taxa seemed to consume encrusting epiphytes, either vegetal or animal. This selective grazing pressure by amphipods may release encrusting epiphytes from competition for space, light and/or nutriments with the fast-growing erected algae, and could thus play an important role in the structuring of the epiphytic cover from P. oceanica leaves. Moreover, this top-down control might keep erected algae biomass to a normal, sustainable level, therefore also benefiting the seagrass itself. Our results also indicate that amphipod trophic activity caused nitrogen enrichment in both grazed (erected algae) and non-grazed (encrusting algae & seagrass leaves) vegetal tissues. A plausible interpretation could be that sloppy feeding and excretion by the grazers enhanced availability of this nutrient, which is typically limiting for photosynthesis in shallow P. oceanica meadows. This emphasizes the fact that grazing is not a simple negative interaction, but that it can also benefit the primary producers. Our results thus indicate that amphipods from P. oceanica meadows seem to be bound to the epiphytic cover of the leaves by complex and multilateral trophic interactions, and have an indirect influence on the seagrass itself. Amphipods may therefore play an important part in the functioning of the epiphyte/seagrass/grazer system of these meadows, and thus act as ecosystems engineers. This abstract is dedicated to the freshly born Adèle and Côme. [less ▲]

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See detailPotential early indicators of anthropogenically derived nutrients : a multiscale stable isotope analysis
Vermeulen, Simon ULg; Sturaro, Nicolas ULg; Gobert, Sylvie ULg et al

in Marine Ecology. Progress Series (2011), 422

Increasing human pressure along Mediterranean coastlines raises the need to define sensitive bioindicators that provide an early response to nutrient enrichment. We performed multiscale carbon and ... [more ▼]

Increasing human pressure along Mediterranean coastlines raises the need to define sensitive bioindicators that provide an early response to nutrient enrichment. We performed multiscale carbon and nitrogen stable isotope analyses on the limpet Patella caerulea, the snail Monodonta turbinata, epilithic biofilms, and the macroalga Rissoella verruculosa inhabiting the rocky midlittoral zone. Samples were seasonally collected in 2006 from 5 sites exposed to a range of anthropogenic discharges in the Revellata Bay area and in Marseille harbour (France). All bioindicators exhibited strongly elevated δ15N values at impacted sites compared to pristine ones, which revealed the biological availability of anthropogenically derived nutrients. Only epilithic biofilms tended to show both the occurrence of nutrient pulses during the tourist season and a δ13C response at impacted sites. In contrast to macroalgae, which exhibited a somewhat equivocal signal, gastropods and especially M. turbinata provided the best time-integrated picture of the graduated exposure of the 5 sites to anthropogenic impact. Results also showed first evidence of large isotopic variability at a scale of tens of metres, close to that found at the kilometre scale. The intra- and interspecific isotopic variability in gastropods may be explained by the patchiness of resources and specific morphological and behavioural features, but these factors do not greatly hamper their potential as early bioindicators of wastewater disturbances. [less ▲]

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See detailDistribution patterns of Caprella tavolarensis (Crustacea: Amphipoda) in the Tavolara-Punta Coda Cavallo Marine Protected Area.
Sturaro, Nicolas ULg; Gobert, Sylvie ULg; Lepoint, Gilles ULg et al

in Biologia Marina Mediterranea (2011), 18(1), 290-291

Distribution patterns of Caprella tavolarensis was investigated at the tavolara-punta Coda Cavallo Marine protected area. results revealed that C. tavolarensis abundance may exhibit spatial patterns ... [more ▼]

Distribution patterns of Caprella tavolarensis was investigated at the tavolara-punta Coda Cavallo Marine protected area. results revealed that C. tavolarensis abundance may exhibit spatial patterns associated with the protection status of the zones, highlighting the importance of totally protected areas in species conservation and management. [less ▲]

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See detailEpilithic biofilm as a key factor for small-scale river fisheries on Caribbean Islands
Lefrançois, E.; Coat, Sophie; Lepoint, Gilles ULg et al

in Fisheries Management & Ecology (2011)

Numerous freshwater species are consumed or exploited through artisanal fisheries in the rivers of the islands of Guadeloupe, French West Indies. Autochthonous production of organic matter is limited in ... [more ▼]

Numerous freshwater species are consumed or exploited through artisanal fisheries in the rivers of the islands of Guadeloupe, French West Indies. Autochthonous production of organic matter is limited in these flowing rivers and is mainly represented by scarce filamentous green algae and an abundant epilithic biofilm growing on wet stones in the river bed. Stable isotope analysis was used to quantify the relative importance of biofilm and other riverine allochthonous and autochthonous food sources in the diet of tropical shrimps (Palaemonidae, Atyidae and Xiphocarididae) and fishes (Gobiidae and Eleotridae) consumed by the local people. The epilithic biofilm was exploited by most species, constituted an important source of autochthonous carbon and wasan important source of organic matter production at the base of freshwater food webs in Caribbean rivers. Biofilm percentages in the diet reached 32% for molluscs, 85% for atyid shrimps, 29% for xiphocaridid shrimps, 14% for palaemonid shrimps and 13% for fish. Assessment of biofilm in nine rivers showed that blue and red cyanobacteria were quantitatively dominant with a moderately rich diatom flora. These results address the interactions between river biofilm and Caribbean freshwater fauna where trophic links between consumers and their potential resources have poorly been documented. [less ▲]

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See detailRelationship between PCB 153 and stable nitrogen in a Guiana dolphin (Sotalia guianensis) food weeb, Gunabara Bay, Brazil
Vidal, L. G.; Bisi, T. L.; Dorneles, P. R. et al

in Organohalogen Compounds (2011)

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See detailOrganochlorine pollution in tropical rivers (Guadeloupe): Role of ecological factors in food web bioaccumulation
Coat, Sophie; Monti, Dominique; Legendre, Pierre et al

in Environmental Pollution (2011), 159

Concentrations of organochlorine pesticides and stable isotope ratios of nitrogen and carbon were measured in a tropical freshwater ecosystem to evaluate the contamination level of biota and examine the ... [more ▼]

Concentrations of organochlorine pesticides and stable isotope ratios of nitrogen and carbon were measured in a tropical freshwater ecosystem to evaluate the contamination level of biota and examine the bioaccumulation patterns of pollutants through the food web. Chemical analyses showed a general and heavy contamination of the entire food web. They revealed the strong accumulation of pollutants by juveniles of diadromous fishes and shrimps, as they re-enter the river. The role of ecological factors in the bioaccumulation of pesticides was evaluated. Whereas the most persistent pollutants (chlordecone and monohydro-chlordecone) were related to the organisms diet and habitat, bioaccumulation of b-HCH was only influenced by animal lipid content. The biomagnification potential of chlordecone through the food chain has been demonstrated. It highlighted the importance of trophic transfer in this compound bioaccumulation process. In contrast, bioconcentration by passive diffusion from water seemed to be the main exposure route of biota to b-HCH. [less ▲]

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See detailToothed whales in the northwestern Mediterranean: Insight into their feeding ecology using chemical tracers
Praca, Emilie; Laran, Sophie; Lepoint, Gilles ULg et al

in Marine Pollution Bulletin (2011), 62(5), 1058-1065

Risso’s dolphins, pilot whales and sperm whales rarely strand in the northwestern Mediterranean. Thus, their feeding ecology, through the analysis of stomach contents, is poorly known. The aim of this ... [more ▼]

Risso’s dolphins, pilot whales and sperm whales rarely strand in the northwestern Mediterranean. Thus, their feeding ecology, through the analysis of stomach contents, is poorly known. The aim of this study was to gain further insight into the segregation/superposition of the diet and habitat of Risso’s dolphins, pilot whales and sperm whales using chemical tracers, namely, stable isotopes (d13C, d15N) and orga- nochlorines. Significantly different d15N values were obtained in Risso’s dolphins (11.7 ± 0.7‰), sperm whales (10.8 ± 0.3‰) and pilot whales (9.8 ± 0.3‰), revealing different trophic levels. These differences are presumably due to various proportions of Histioteuthidae cephalopods in each toothed whale’s diet. Similar d13C contents between species indicated long-term habitat superposition or corroborated impor- tant seasonal migrations. Lower congener 180 concentrations (8.20 vs. 21.73 lg.g􏰀1 lw) and higher tDDT/ tPCB ratios (0.93 vs. 0.42) were observed in sperm whales compared with Risso’s dolphins and may indi- cate wider migrations for the former. Therefore, competition between these species seems to depend on different trophic levels and migration patterns. [less ▲]

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See detailImportance of copepod carcasses versus faecal pellets in the upper water column of an oligotrophic area
Frangoulis, Constantin; Skliris, Nikolaos; Lepoint, Gilles ULg et al

in Estuarine Coastal & Shelf Science (2011), 92

Downward flux of zooplankton faecal pellets and carcasses was studied during and after the spring bloom in an oligotrophic coastal area of the Western Mediterranean using a « swimmer-excluding » sediment ... [more ▼]

Downward flux of zooplankton faecal pellets and carcasses was studied during and after the spring bloom in an oligotrophic coastal area of the Western Mediterranean using a « swimmer-excluding » sediment trap. Zooplankton detritus retrieved in the trap were comprised of cylindrical faecal pellets (from meso- and macrozooplankton) and copepod carcasses with a respective carbon flux of 0.05 - 2.69 mg m-2 d-1 and 0.42 - 4.37 mg m-2 d-1. Carbon and nitrogen flux of carcasses always exceeded that of faecal pellets, except at the beginning of the bloom due to a higher contribution of macrozooplankton faecal material. During the peak of phytoplankton biomass, total faecal flux essentially comprised of copepod faecal pellets (68 - 86% of the total faecal carbon), whereas before and after this period, macrozooplankton faecal material dominated (88 - 91% of total faecal carbon flux). Copepod faecal flux was positively correlated with phytoplankton biomass. Estimates of non-predatory biomass mortality rates (from < 0.01 to 0.05 d-1) were negatively correlated with chl a with a time lag of 12 days and were lower than predatory mortality values reported in the same area. The paper discusses the relative importance of carcasses versus faecal pellet flux and of non-predatory versus predatory mortality, as well as the potential role of these zooplankton detritus in supporting the production of benthos in oligotrophic areas. [less ▲]

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See detailFeeding ecology and phylogenetic structure of a complex neotropical termite assemblage, revealed by nitrogen stable isotope ratios
Bourguignon, Thomas; Sobotnik, Jan; Lepoint, Gilles ULg et al

in Ecological Entomology (2011), 36(2), 261-269

2. Nitrogen stable isotopes (hereafter delta 15N) were used to place termites from French Guiana rainforests along a wood-soil decomposition gradient, to test (i) whether feeding group assignation based ... [more ▼]

2. Nitrogen stable isotopes (hereafter delta 15N) were used to place termites from French Guiana rainforests along a wood-soil decomposition gradient, to test (i) whether feeding group assignation based on morphological characters was accurate and actually represented diet specialisation thresholds, and (ii) to what extent the dietary specialization of species is explained by phylogeny (phylogenetic autocorrelation). 3. delta 15N values vary over a range of 13 parts per thousand, suggesting that diet diversification contributes to the high species diversity in French Guiana. delta 15N values span a similar interval in all Termitidae subfamilies. Ranges of different subfamilies broadly overlap, although each of them diversified preferentially on one side of the wood-soil decomposition gradient. Congeneric species share similar feeding habits, whereas distant species tend to feed on distinct substrates. 4. Feeding groups did not completely match stable isotope data: there was no discontinuity between Groups III and IV, and no correlation between anatomical criteria used to distinguish these groups and delta 15N values. Nor was there any consistent difference in delta 15N values between wood feeders of the families Rhinotermitidae (Group I) and Termitidae (Group II). We also suggest that species feeding outside the wood-soil gradient should be distinguished for their peculiar feeding requirements. [less ▲]

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See detailEffects of shading and sediment alterations on Posidonia oceanica meadows: in situ experiments
Pete, Dorothée ULg; Velimirov, Branko; Lepoint, Gilles ULg et al

Conference (2010, November 24)

In the Mediterranean Sea, the seagrass Posidonia oceanica is affected by many threats from anthropogenic sources. One of them is the increasing development of fish farming, which is responsible of the ... [more ▼]

In the Mediterranean Sea, the seagrass Posidonia oceanica is affected by many threats from anthropogenic sources. One of them is the increasing development of fish farming, which is responsible of the destruction of some meadows. Within troubles cause by those fish farms on the surrounding environment, the increase of phytoplankton biomass in the water column (leading to a shading effect) and a modification of the sediment are often cited as a reason of seagrass disappearance. To understand how those troubles are affecting P. oceanica and its sedimentary compartment, in situ experiments were led during three months, from the end of May til the end of August 2009, in STARESO (STAtion de REcherches Sous-marines et Océanographiques, Corsica, France), at a depth of 10 meters. The shading was mimicked by three replicated shading frames (3 x 1 m), which stopped around 50 % of the incident light. To modify the sedimentary compartment, some sediment was taken from under the fish farm of Calvi (Corsica, France) and added once a week on marked zones in the seagrass meadow. Those sites were compared with a control site, situated in the same meadow. Samples were taken once a month and consisted in pore water, sediment cores and shoots of P. oceanica. An estimation of the density of the meadow in every sampling zones was also performed. Measured parameters are the concentration of nutrients in pore water, grain size, redox potential discontinuity (RPD), biomass of bacteria, organic matter, meiofauna and microphytobenthos within the sediment, total carbon and nitrogen in the sediment and leaves, the length, width and biomass of leaves and shoots, the biomass of epiphytes and the content of chlorophyll a in leaves. During those experiments, Posidonia oceanica was not very affected. However, some parameters of the sedimentary compartment were modified (RPD, biomass of bacteria, organic matter, nutrients in pore water,…), suggesting a modification in the functioning of the ecosystem. These results are important because they show that the sedimentary compartment reacts more rapidly to threats then the seagrass itself. So, it could be an interesting tool in quality assessments. [less ▲]

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See detailThe role of meiofauna in energy transfer in a Mediterranean seagrass bed (Calvi, Corsica)
MASCART, THIBAUD; Lepoint, Gilles ULg; Borges, Alberto ULg et al

Poster (2010, October 22)

Meiofaunal communities of the endemic Mediterranean seagrass, Posidonia oceanica, were sampled in five different habitats characterised by different degradation level of macrophytodetritus. In term of ... [more ▼]

Meiofaunal communities of the endemic Mediterranean seagrass, Posidonia oceanica, were sampled in five different habitats characterised by different degradation level of macrophytodetritus. In term of abundance, harpacticoid copepods represent half of the community followed by nematodes and polychaetes. Two meiofauna communities were distinguished: (1) a benthic community of meiofauna, living in the sediment or on highly fragmented macrophytodetritus, and (2) a foliar, epiphytal community associated with seagrass leaves and low fragmented macrophytodetritus leaves. They differed significantly in their harpacticoid copepod family composition. The benthic community consisted mainly of families like Tisbidae and Miraciidae, while the epiphytal community was dominated by families like Thalestridae and Laophontidae. These differences in composition may also imply a differential functional diversity. Trophic biomarkers (stable isotopes, fatty acids) were used to identify the major sources of organic matter contributing to the copepods diet and hence to gain insight in the overall carbon flux. Harpacticoid copepods showed preferences to feed upon the epiphytal biofilm community composed of bacteria, diatoms, fungi and microalgae. Copepods used the seagrass and detritus material merely as substrate, but were attracted to the biofilm rather than the plant material which is rich in structural carbohydrates difficult to assimilate by animals (i.e. lignin, cellulose, ...). Since harpacticoid copepods showed to use different sources of carbon, unravelling the contribution of each of them and the role of the degradation level of the detritus for food selectivity is the next step forward. [less ▲]

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See detailImpact of grazing by amphipods on the epiphytic cover of the Posidonia oceanica leaves: an in situ experiment.
Michel, Loïc ULg; Dupont, Alessandra; Gobert, Sylvie ULg et al

Poster (2010, October 22)

It is now established that several species of amphipods associated to Mediterranean Posidonia oceanica meadows consume the macro-epiphytes present on the leaves of the seagrass. Moreover, under controlled ... [more ▼]

It is now established that several species of amphipods associated to Mediterranean Posidonia oceanica meadows consume the macro-epiphytes present on the leaves of the seagrass. Moreover, under controlled in vitro conditions, three amphipod taxa (Apherusa chiereghinii,Dexamine spiniventris and Gammarus spp.) are able to drastically deplete the biomass of erected algae, thus influencing the epiphytic cover in both a quantitative and a qualitative way. Here, we tried to assess whether this strong and complex trophic interaction was realized in the field. We designed an in situ experiment that used microcosms placed directly in the meadow, at a depth of 10m, to estimate the impact of grazing by the aforementioned amphipod taxa on the dynamics of the epiphytic cover. Both Gammarus spp. and Dexamine spiniventris caused a significant decrease of the biomass of erected algae and erected animals (bryozoans and hydrozoans). Impact of grazing by Apherusa chiereghinii on these two epiphytic groups was less important, although strong but marginally non-significant (0,1>p>0,05) trends to lower biomasses were present. None of the considered taxa seemed to consume encrusting macro-epiphytes. In addition, assimilation of epiphyte-derived carbon and nitrogen by grazers was monitored using stable isotopes (13C and 15N), and epiphyte elemental content (C & N) was measured. Our results shed light on trophic interactions between the amphipods from Posidonia oceanica meadows and the seagrass epiphytic cover, and thus enhance our understanding of the role of these grazers in the functioning of the meadow as an ecosystem. [less ▲]

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See detailTop-down role of fish predators in structuring amphipod community associated to Posidonia oceanica seagrass meadows
Sturaro, Nicolas ULg; Lepoint, Gilles ULg; Panzalis, Pier et al

Poster (2010, October)

Despite the major ecological importance of Posidonia oceanica seagrass meadows in the Mediterranean Sea, little attention has been given to community structuring forces by predators in this ecosystem. To ... [more ▼]

Despite the major ecological importance of Posidonia oceanica seagrass meadows in the Mediterranean Sea, little attention has been given to community structuring forces by predators in this ecosystem. To better understand the mechanisms by which fishes affect amphipod community structure associated to P. oceanica beds, experimental manipulations of predation intensity (enclosure and exclusion cages) were set up in the Tavolara-Punta Coda Cavallo Marine Protected Area (Sardinia, NW Mediterranean). In totally protected area, where high abundance of predatory fishes is recorded, we have performed exclusion experiment. Total amphipod abundance increased at the end of the experiment, but diversity and specific composition were unaffected. At the species taxonomic level, significant increase in abundance between treatments appeared only for Caprella acanthifera. In partially protected area, where fish abundance is lower and amphipod abundance higher, individuals of the carnivorous fish Coris julis (Labridae) were enclosed in cages to provide an estimate of the potential for this species to impact on amphipod community. There was a small but measurable effect on amphipod abundance between enclosures and unmanipulated controls. A few dominant amphipod species responded to fish predation by significant decrease in abundance. These results suggest that fish predation may determine the relative abundances in the community of some amphipod species and to some degree, through an untested link with habitat complexity, determine the spatial distribution of amphipod abundance within P. oceanica beds. Moreover, patterns observed at the species level, suggest parallel complex interactions probably mainly related to ecological behaviour of amphipod species. [less ▲]

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See detailShading and alterations of the sediment: in situ experiments to mimic impacts of fish farms on a Mediterranean coastal ecosystem
Pete, Dorothée ULg; Velimirov, Branko; Lepoint, Gilles ULg et al

Poster (2010, October)

In the Mediterranean coastal zone, the seagrass Posidonia oceanica forms underwater meadows which sustain a high biodiversity and has many important roles (production of oxygen, protection of coasts ... [more ▼]

In the Mediterranean coastal zone, the seagrass Posidonia oceanica forms underwater meadows which sustain a high biodiversity and has many important roles (production of oxygen, protection of coasts, ...). Unfortunately, they are more and more threaten, notably by the increasing development of aquaculture. Indeed, fish farms increase the biomass of phytoplankton organisms in the water column (leading to a shading effect) and modify the sediment, which entail the disappearance of the seagrass. To understand the impact of those troubles on P. oceanica and the ecosystem, in situ experiments were led during three months, in STARESO (STAtion de Recherches Sous- marines et Océanographiques; Calvi, Corsica), at a depth of 10 meters. The shading was mimicked by shading frames, which stopped around 50 % of the incident light. To modify the sedimentary compartment, sediment was taken from under the aquaculture of Calvi and added once a week on marked zones in the meadow. Those sites were compared with a control site, situated near them. Measured parameters are: the concentration of nutrients in pore water, grain size, redox potential discontinuity, biomasses of bacteria, organic matter, meiofauna and microphytobenthos within the sediment, the length, width, biomass and chlorophyll a content of P. oceanica leaves and the biomass of epiphytes. During those experiments, P. oceanica was not very affected although some parameters of the sedimentary compartment were modified. These results show that the sedimentary compartment reacts more rapidly to threats then the seagrass itself. So, it could be an interesting tool in quality assessments. [less ▲]

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See detailAssessment of gestation, lactation and fasting on stable isotope ratios in northern elephant seals (Mirounga angustirostris)
Habran, Sarah ULg; Debier, Cathy; Crocker, Dan E. et al

in Marine Mammal Sciences (2010), 26(4), 880-895

Effects of physiological processes such as gestation, lactation and nutritional stress on stable isotope ratios remain poorly understood. To determine their impact, we investigated these processes in ... [more ▼]

Effects of physiological processes such as gestation, lactation and nutritional stress on stable isotope ratios remain poorly understood. To determine their impact, we investigated these processes in simultaneously fasting and lactating northern elephant seals (Mirounga angustirostris). Stable carbon and nitrogen isotope values were measured in blood and milk of 10 mother-pup pairs on days 5 and 22 of lactation. As long- and short-term integrators of diet, blood cells and serum may reflect foraging data or energy reserves from late gestation and lactation, respectively. Limited changes in isotopic signatures of maternal blood over the lactating period were highlighted. Nitrogen isotope fractionation associated with mother-to-offspring transfer of nutrients was generated between mother and offspring during gestation and lactation. This fractionation was tissue and time-specific, it varied between early and late lactation from +0.6‰ to +1.3‰ in blood cells and from +1.1‰ to nonsignificant value in serum. Therefore, if pups appear to be good proxies to investigate the female trophic ecology especially for C sources, much more caution is required in using δ15N values. Further studies are also needed to better define the relative impact of fasting and lactation on the enrichment or depletion of isotopes in different tissues. [less ▲]

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See detailImpact of grazing by amphipods on the dynamics of the epiphytic cover of the Posidonia oceanica leaves : an in vitro experiment.
Michel, Loïc ULg; Gobert, Sylvie ULg; Dauby, Patrick ULg et al

Conference (2010, September 17)

It is now established that several species of amphipods associated to Mediterranean Posidonia oceanica meadows consume the epiphytes present on the leaves of the seagrass. However, little or no work has ... [more ▼]

It is now established that several species of amphipods associated to Mediterranean Posidonia oceanica meadows consume the epiphytes present on the leaves of the seagrass. However, little or no work has been undertaken to quantify this interaction. Here, we present the results of an in vitro experiment that used seagrass mimics to estimate the impact of grazing by the amphipods Apherusa chiereghinii, Dexamine spiniventris and Gammarus spp on the dynamics of the epiphytic cover. All species reduced epiphyte biomass in a significant way, and grazers preferentially fed on erected algae. Assimilation of epiphyte-derived carbon and nitrogen was monitored using stable isotopes (13C and 15N) labelling, and was obvious in the three taxa. Moreover, grazing activity of amphipods seemed to influence epiphyte physiology, notably by increasing nitrogen uptake by the erected algae. These results shed light on trophic interactions between the amphipods from Posidonia oceanica meadows and the seagrass epiphytic cover, and thus enhance our understanding of the role of these grazers in the functioning of the meadow as an ecosystem. [less ▲]

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See detailThe role of fish predation in the structure of amphipod community associated with Posidonia oceanica seagrass meadows
Sturaro, Nicolas ULg; Lepoint, Gilles ULg; Panzalis, Pier et al

Conference (2010, September)

Despite the major ecological importance of Posidonia oceanica seagrass meadows in the Mediterranean Sea, little attention has been given to community structuring forces by predators in this ecosystem. To ... [more ▼]

Despite the major ecological importance of Posidonia oceanica seagrass meadows in the Mediterranean Sea, little attention has been given to community structuring forces by predators in this ecosystem. To better understand the mechanisms by which fishes affect amphipod community structure associated to P. oceanica beds, experimental manipulations of predation intensity (enclosure and exclusion cages) were set up in the Tavolara-Punta Coda Cavallo Marine Protected Area (Sardinia, NW Mediterranean). In totally protected area, where high abundance of predatory fishes is recorded, we have performed exclusion experiment. Total amphipod abundance increased at the end of the experiment, but diversity and specific composition were unaffected. At the species taxonomic level, significant increase in abundance between treatments appeared only for Caprella acanthifera. In partially protected area, where fish abundance is lower and amphipod abundance higher, individuals of the carnivorous fish Coris julis (Labridae) were enclosed in cages to provide an estimate of the potential for this species to impact on amphipod community. There was a small but measurable effect on amphipod abundance between enclosures and unmanipulated controls. A few dominant amphipod species responded to fish predation by significant decrease in abundance. These results suggest that fish predation may determine the relative abundances in the community of some amphipod species and to some degree, through an untested link with habitat complexity, determine the spatial distribution of amphipod abundance within P. oceanica beds. Moreover, patterns observed at the species level, suggest parallel complex interactions probably mainly related to ecological behaviour of amphipod species. [less ▲]

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See detailMultiparametric observations and analysis in the Bay of Calvi (Corsica), an ideal site for studying the human activity effects and climate changes in the Mediterranean Sea; STARESO
Gobert, Sylvie ULg; Alvera Azcarate, Aïda ULg; Barth, Alexander ULg et al

Conference (2010, May)

STARESO (Station de REcherche Sous marine et Océanographique) is the marine and oceanographic research station of the University of Liège (Belgium) managed by the French company STARESO S.A.. Constructed ... [more ▼]

STARESO (Station de REcherche Sous marine et Océanographique) is the marine and oceanographic research station of the University of Liège (Belgium) managed by the French company STARESO S.A.. Constructed in 1969, it is located near Calvi (Corsica, Western Mediterranean Sea) in an oligotrophic area chosen for the exceptional quality of its coastal waters STARESO offers to the oceanographers, by diving or with boats, a direct access to the sea. The variety of the accessible ecosystems is remarkable and unique in the Mediterranean basin: -the Bay of Calvi is characterized by healthy and very diverse biocenosis (e.g. Posidonia meadows, rocky and sandy communities, -a steep submarine canyon, with depths greater than 1 000 meters, is accessible in 15 minutes of navigation; -the Liguro-Provençal front, a major hydrologic structure, is situated between 10 and 15 miles of the coast. STARESO is accessible all the year for everybody and is functioning like an oceanographic research vessel. The Station is a platform for all oceanographic disciplines with a scientific expertise widely based on a long tradition of interdisciplinary work, and a direct access to time series of physical, chemical and biological data registered with automated systems and variety of sensors deployed in the Bay of Calvi since 30 years. This platform provides the opportunity to reach coastal, pelagic, benthic, deep systems with a manageable cost and ship requirements in a pristine zone. [less ▲]

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