References of "Gobert, Sylvie"
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See detailDistribution of inorganic and organic contaminants in the intertidal surface sediments along the Hugli River Estuary, eastern part of India
Das, Krishna ULg; Sarkar, Santosh; Thomé, Jean-Pierre ULg et al

Conference (2016, February 17)

Hooghly estuary and coastal environment in north east coast of India has been strongly affected by the rapid human settlements, intensive boating and tourist activities, deforestation and ongoing ... [more ▼]

Hooghly estuary and coastal environment in north east coast of India has been strongly affected by the rapid human settlements, intensive boating and tourist activities, deforestation and ongoing agricultural and aquacultural practices. The present work investigated trace elements (TEs, T-Hg, Al, V, Cr, Fe, Mn, Cu, Zn, Co, Ni, Ca, Sr, Li, Be, P, Mo, Ag, Cd, Sn, Sb, Ba, Pb, Bi, U, As, Se) and organohalogen compounds in surface sediment (top 0-10cm) considering 8 sampling sites along the Hugli River Estuary (HRE), India. The studied organic compounds include polychlorobiphenyls (PCBs), hexachlorocyclohexane isomers (HCHs), dichlorodiphenyltrichloroethane and metabolites (DDTs) and polybromodiphenyl ethers (PBDEs). Textural analyses of the sediment reveal an overall dominance of mud. All trace elements could be detected at variable concentrations in the following descending order: Al>Fe>Ca> P>Mn> Cu> Zn> Ba >V >Cr>Sr>Ni> Li >Co >Pb>As >Se >U >Be >Sn>Bi >Ag >Mo >Cd >Sb. A synchronous enrichment of majority of the elements were observed at the site Gangasagar (~100 km south megacity Calcutta), situated at the confluence of Hugli River and Bay of Bengal, which might be attributed to cumulative impact of the physicochemical processes and multiple anthropogenic sources. It is revealed that PCBs and DDTs were the dominant compounds among the organic pollutants accounting concentrations up to 23.5 ng.g-1 and 4.4 ng.g-1 respectively at the site Babughat, adjacent to the megacity Calcutta. The results have implications for pollution in complex estuarine environment in a meso-macrotidal setup where there is significant influx of sediments carrying huge load of inorganic and organic pollutants mainly due to rapid urbanization and industrialization. [less ▲]

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See detailDominant amphipods of Posidonia oceanica seagrass meadows display considerable trophic diversity
Michel, Loïc ULg; Dauby, Patrick ULg; Gobert, Sylvie ULg et al

in Marine Ecology (2015), 36(4), 969-981

Gut content examination and trophic markers (fatty acids, stables isotopes of C and N) were combined to delineate the diet of the dominant species of amphipods from Mediterranean Posidonia oceanica ... [more ▼]

Gut content examination and trophic markers (fatty acids, stables isotopes of C and N) were combined to delineate the diet of the dominant species of amphipods from Mediterranean Posidonia oceanica seagrass meadows and to highlight trophic diversity among this community. Our results indicate that, although all dominant species heavily relied on macroalgal epiphytes, considerable interspecific dietary differences existed. Carbon stable isotope ratios notably showed that some of the amphipod species favored grazing on epiphytes from leaves or litter fragments (Apherusa chiereghinii, Aora spinicornis, Gammarus aequicauda), while others like Dexamine spiniventris preferred epiphytes from rhizomes. The remaining amphipods (Caprella acanthifera, Ampithoe helleri and Gammarella fucicola) readily consumed both groups. In addition, SIAR modeling suggested that most species had a mixed diet, and relied on several food items. Fatty acid analysis and gut contents revealed that contribution of microepiphytic diatoms and of benthic and suspended particulate organic matter to the diet of amphipods were anecdotal. None of the examined species seemed to graze on their seagrass host (low 18:2(n-6) and 18:3(n-3) fatty acids contents), but G. aequicauda partly relied on seagrass leaf detritus, as demonstrated by the lesser 13C-depletion of their tissues. Overall, our findings suggest that amphipods, because of their importance in transfers of organic matter from primary producers and detritus to higher rank consumers, are key-items in P. oceanica associated food webs. [less ▲]

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See detailSTAtion of Reference and rEsearch on Change of local and global Anthropogenic Pressures on Mediterranean Ecosystems Drifts: The STARECAPMED project
Richir, Jonathan ULg; Abadie, Arnaud ULg; Binard, Marc ULg et al

Conference (2015, November 08)

The Marine and Oceanographic Research Station STARESO in the Calvi Bay, Corsica (France), is a unique tool in a preserved natural site that includes all the characteristic ecosystems of the Mediterranean ... [more ▼]

The Marine and Oceanographic Research Station STARESO in the Calvi Bay, Corsica (France), is a unique tool in a preserved natural site that includes all the characteristic ecosystems of the Mediterranean littoral. The station, established in 1970, has archived environmental data for decades. The STARECAPMED project, multidisciplinary, articulates itself around these two main features. Its objective is to understand how human activities can interact with the fundamental processes that govern the functioning of the different coastal ecosystems of a Mediterranean bay. The understanding of these interactions involves: (i) the identification of the anthropogenic pressures; (ii) the quantification of their impacts on the ecosystems; (iii) the prioritization of these impacts. STARECAPMED also aims to confirm the relevance of the use of the Calvi Bay as a reference in the study of local and global pressures and the changes they may cause on the structure and the functioning of Mediterranean coastal ecosytems. [less ▲]

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See detail) The spatial variability of trace element bioaccumulation processes: Tools to environmental management
Richir, Jonathan ULg; Lejeune, Lejeune; Lepoint, Gilles ULg et al

Conference (2015, November 07)

As transitional environments, coastal meadows are particularly vulnerable to pollution. Trace elements remain contaminants of concern because of their persistence, their ability to accumulate in biota and ... [more ▼]

As transitional environments, coastal meadows are particularly vulnerable to pollution. Trace elements remain contaminants of concern because of their persistence, their ability to accumulate in biota and their toxicity. Local, regional, national and cross-border programs are thus initiated to monitor their environmental occurrence. Sentinel organisms, or bioindicators, have been widely used to this end since they accumulate the bioavailable and thus potentially toxic fraction of contaminants. In the framework of the STARECAPMED project, the accumulation of trace elements in the seagrass Posidonia oceanica (L.) Delile was studied at different spatial scales: along a radial (100 m scale), in a bay (1 km scale), along the French Mediterranean littoral (10-100 km scale) and along the whole Mediterranean coastline (100-1000 km scale). Results showed that the contamination of the sampled shoots could vary as much at opposite scales. This benthic primary producer accumulates contaminants sequestered in the sediments, in addition to their dissolved fraction in the water column. The sediments also offer a time integration of coastal pollution and thus amplify the pollution signal recorded by the seagrass, resulting in the observed spatial variability. These results demonstrate that the in-depth knowledge of the ecology of the monitored bioindicator and the interactions it shares with its environment cannot be ignored. Such failure could lead to erroneous interpretations of the levels of contamination of monitored sites, and points out the need to define a sampling strategy based on the monitoring objectives and the selected bioindicator. [less ▲]

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See detailThe trace element contamination of coastal waters: A holistic approach to environmental monitoring surveys
Richir, Jonathan ULg; Gobert, Sylvie ULg

Conference (2015, November 07)

Sustained monitoring programs are necessary to evidence the efficacy of regulatory controls on pollutant discharges and to assess the health status of ecosystems. Within this perspective, this study aimed ... [more ▼]

Sustained monitoring programs are necessary to evidence the efficacy of regulatory controls on pollutant discharges and to assess the health status of ecosystems. Within this perspective, this study aimed to monitor the coastal trace element contamination of the whole Mediterranean, using Posidonia oceanica (L.) Delile as bioindicator. But sustainable coastal management also requires the development of appropriate classification systems intended, among other purposes, for environmental managers and policy makers. The combined utilization of several complementary monitoring tools - water quality scale, pollution index, spatial analysis - successfully led to the development of such an operational classification system: it allowed to assess contamination threats and to depict contamination gradients of the entire Mediterranean, while assessing more regional and local impacts. Consequently, such holistic approaches should be privileged to accurately monitor the contamination rate of coastal waters and to transfer relevant information on this composite problem to environmental managers and policy makers. [less ▲]

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See detailDGTs, a complementary tool towards more efficient biomonitoring practices
Richir, Jonathan ULg; Lepoint, Gilles ULg; Donnay, Annick et al

Conference (2015, October 01)

Among the diversity of contaminants, trace elements (TEs) remain of concern because of their persistence, their ability to accumulate in biota and their toxicity. The direct measurement of their dissolved ... [more ▼]

Among the diversity of contaminants, trace elements (TEs) remain of concern because of their persistence, their ability to accumulate in biota and their toxicity. The direct measurement of their dissolved concentrations only gives punctual and fluctuating information, and often remains below detection limits of analytical methods. The more appropriate use of sentinel organisms, or bioindicators, to monitor TEs has thus often been preferred in environmental surveys. The introduction of the diffusive gradients in thin films (DGTs) technique has however participated to progressively change this binary view - bioindicator vs water - of the coastal monitoring of TEs, and DGTs rapidly became a relevant complementary tool to bioindicators, has illustrated below. In the framework of the STARECAPMED project, the ecology and the ecotoxicology of TEs were studied in the seagrass Posidonia oceanica (L.) Delile and the mussel Mytilus galloprovincialis Lamarck, 1819. DGTs (free- and pore-water probes) were deployed before sampling of organisms. TEs were also analyzed in suspended matter (dissolved and suspended-particulate TE speciation). Studies were performed in the Calvi Bay (Corsica, France), northwestern Mediterranean. TE concentrations in organisms and suspended matter or in DGT resins were measured by DRC-ICP-MS after HNO3/H202 mineralization or after a 24h elution in HNO3 1M, respectively. (1) TE bioaccumulation was first seasonally studied in P. oceanica over 3 years. Dissolved TE concentrations monitored with DGTs were low to very low. TE bioaccumulation dynamics in P. oceanica could thus be linked to the natural physiological cycle of the plant, in clean environmental conditions. (2) To complement that field survey, isolated seagrasses were in situ contaminated with TEs at environmental relevant concentrations. Through the use of DGTs, TE uptake kinetics were modelled for seagrasses exposed to know bioavailable concentrations of contaminants, as were loss kinetics during the following depuration phase. The TE sequestration ability of a healthy P. oceanica meadow facing sudden trace metal contamination events could also be quantified. (3) The deployment of pore-water DGT probes in bare-sand or seagrass colonized sediments further showed that, through its stabilizing function of the seabed, P. oceanica maintained higher TE levels in the pore-water. P. oceanica meadows thus offer a significant “depuration-filtering” ecological service along highly anthropized Mediterranean coasts. M. galloprovincialis are widely used in large spatial scale coastal monitoring surveys. (4) The deployment of caged mussels together with DGTs showed that the little contaminated water body of the Calvi Bay was relatively homogenous. It also allowed to calculate TE bioaccumulation towards mussels in reference conditions, and to compare it to native mussel populations. (5) Finally, during a 5 months mussel caging survey, mussels and suspended matter were collected weekly to monthly, such as were deployed DGTs. The physiological status of mussels, the speciation of TEs between their dissolved and suspended-particulate phases, and their relative influence on TE bioaccumulation dynamics in mussels were investigated. In conclusion, these case studies properly demonstrate how DGT probes can be used as a relevant and complementary tool to bioindicators. Their concomitant use should therefore be privileged in monitoring surveys. [less ▲]

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See detailTrace metal speciation? An essential aspect of biomonitoring to avoid wrong conclusions
Richir, Jonathan ULg; Lepoint, Gilles ULg; Donnay, Annick et al

Poster (2015, September 29)

The Mediterranean mussel Mytilus galloprovincialis is widely used as a bioindicator species in active monitoring surveys. As a filter feeder artificially maintained in the water column, it bioaccumulates ... [more ▼]

The Mediterranean mussel Mytilus galloprovincialis is widely used as a bioindicator species in active monitoring surveys. As a filter feeder artificially maintained in the water column, it bioaccumulates trace metals from the surrounding water in their dissolved and particulate forms. However, most monitoring surveys don’t take into account that speciation aspect when studying trace metal accumulation kinetics in mussels. In the framework of the STARECAPMED project, we monitored trace metal concentrations in the flesh of mussels together with their “most bioavailable” dissolved and particulate fractions in the water column for almost 5 months (February-June 2011). Mussels were purchased from 2 little contaminated French shellfish farms (SARL Etang de Diane and ferme marine des Aresquiers), placed in several pouches to allow regular sampling, and immerged near the Oceanographic Research Station STARESO in the Calvi bay, northwestern Corsica. Mussels and water samples for suspended matter filtration were collected every week to two weeks, as were deployed DGTs. Seawater samples were filtered through 47 mm hydrophilic PTFE membrane filters with a 0.45 µm pore size until clogging. In the laboratory, mussel flesh and filters were digested in Teflon vessels with acids (HNO3/H202) in a closed microwave digestion lab station. DGT resins were eluted for 24h in 1.0 M HNO3. Trace metal concentrations (Cr, Mn, Co, Ni, Cu, Zn, Ag, Cd, Pb) were measured by DRC-ICP-MS. Analytical accuracy was checked by analyzing CRMs. All the studied metals except Pb and Zn were present in the water column to over 80% in their dissolved form. The contribution of the dissolved pathway was thus likely to be predominant in the oligotrophic Calvi bay. Dissolved trace metals showed little temporal variability of their levels, likely resulting from the integration over time of their levels in the DGT probes and the lack of seasonality of this fraction. In contrast, Zn showed great variability of its particulate fraction during the survey. Such temporal variability was also observed for Cr, more abundant in its particulate form at the end of the survey, and for Mn and Pb that conversely tended to decrease. The dynamic of trace metals in the mussel flesh is regulated by the environmental bioavailability of dissolved and particulate metals, the ecophysiological status of mussels and the trophic conditions of the water body. In the oligotrophic Calvi bay, showing background contamination levels by metals, the trophic conditions played a major role once out of the spring plankton bloom. It led to the increase of metal concentrations measured in the flesh of mussels undergoing starvation. However, some metals such as Cu and Co displayed only little temporal variations of their concentrations, these essential micronutrients being well regulated. The combined study of trace metal bioavailability and mussel ecophysiology in defined environmental conditions allows discriminating against biotic and abiotic factors regulating contaminant uptake in mussels, thus avoiding wrong conclusions about the observed dynamics of the studied contaminants. Mussels are a good proxy of coastal water quality, but their proper use notably requires adjustment of raw contaminant concentrations with trophic status of monitored sites. [less ▲]

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See detailSelective top-down control of epiphytic biomass by amphipods from Posidonia oceanica meadows: implications for ecosystem functioning
Michel, Loïc ULg; Dauby, Patrick ULg; Dupont, Alessandra et al

in Belgian Journal of Zoology (2015), 145(2), 83-93

Mediterranean Posidonia oceanica meadows shelter an important biomass and biodiversity of amphipod crustaceans that graze on epiphytes. However, their actual significance for ecosystem functional ... [more ▼]

Mediterranean Posidonia oceanica meadows shelter an important biomass and biodiversity of amphipod crustaceans that graze on epiphytes. However, their actual significance for ecosystem functional processes is hard to estimate, due to the lack of adequate data. Here, a field microcosm-based inclusion experiment was used to test if three of the dominant taxa of the amphipod community (Apherusa chiereghinii, Dexamine spiniventris and Gammarus spp.) could exert top-down control on seagrass leaf epiphytes. Influence of amphipod activity on nutrient availability for the host species was also investigated. All grazer taxa significantly reduced biomasses of erect macroalgae and erect sessile animals present on leaves. None of them consumed encrusting epiflora or epifauna. This selective top-down control could have important implications for the structure of the epiphytic community of P. oceanica leaves, which is one of the most diverse and abundant of all seagrass species. Grazing activity of all taxa caused higher N content of seagrass leaves, likely through amphipod excretion and/or sloppy feeding. Since P. oceanica meadows often grow in oligotrophic zones where plant growth can be nutrient-limited, this N enrichment could enhance seagrass production. Overall, the ecological interaction between P. oceanica and amphipods could be seen as a facultative mutualistic relationship. Our results suggest that amphipod mesograzers are key-elements in some of the functional processes regulating these complex and yet endangered ecosystems, which are essential components of Mediterranean coastal zones. [less ▲]

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See detailSTARECAPMED (STAtion of Reference and rEsearch on Change of local and global Anthropogenic Pressures on Mediterranean Ecosystems Drifts) - Année 2014. Rapport de recherches.
Richir, Jonathan ULg; Abadie, Arnaud ULg; Binard, Marc ULg et al

Report (2015)

La prise de conscience, par le grand public, de l'impact grandissant de l'homme sur l'océan est récente. Elle se traduit par une volonté politique sincère de correction par des mesures de protection, de ... [more ▼]

La prise de conscience, par le grand public, de l'impact grandissant de l'homme sur l'océan est récente. Elle se traduit par une volonté politique sincère de correction par des mesures de protection, de gestion et de développement durable. Ces politiques, et leurs conséquences économiques et sociétales lourdes, ne peuvent être acceptées que si les décisions se fondent sur des connaissances scientifiques incontestables et montrent des résultats scientifiquement prouvés. Par ailleurs, ces décisions doivent prendre en compte des impacts qui s'opèrent à des échelles de temps et d’espace très variables, de quelques heures à plusieurs dizaines d’années et de quelques mètres à plusieurs milliers de km. En termes politiques, l'information scientifique nécessaire à la prise de décision doit pouvoir couvrir les différentes échelles depuis le niveau local et régional, jusqu'à l'échelle nationale, européenne voire globale, et cela sur le plus long terme possible. Enfin, pour être complète, l'information scientifique sur les écosystèmes marins doit pouvoir répondre à trois questions objectives : (i) quel est l'état? (ii) quelle est l'évolution? (iii) quels sont les mécanismes et processus mis en jeux? et à une question plus prospective : (vi) que peux-t-on prévoir et comment agir? Le présent rapport ne peut pas, à lui seul, refléter toute la richesse du programme STARECAPMED. En 3 ans, STARECAPMED a généré plusieurs centaines de milliers de données nouvelles, ré-exploité plusieurs centaines de publications, rapports et autres enregistrements passés et présents. Le programme a aussi généré de nombreux documents, rapports et mémoires. Enfin, des publications internationales et des thèses de doctorat sont en cours de réalisation ou abouties. Afin de rester lisible, nous avons donc choisi de présenter ce rapport 2014 sous la forme de 12 exemples parmi les travaux en cours. Ces exemples sont traités selon un schéma identique en 4 points simples : (i) La présentation du cas d’étude dans le projet global ; (ii),Les approches innovatrices développées ; (iii),La présentation de résultats marquants ; (iv),Les délivrables de STARECAPMED pour les politiques publiques. [less ▲]

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See detailChanges of macrofauna stable isotope compositions in a very inconstant seagrass detritic habitat: actual diet modification or baseline shift?
Remy, François ULg; Mascart, Thibaud ULg; Dauby, Patrick ULg et al

Conference (2015, May 20)

Decayed leaves of the Neptune grass Posidonia oceanica, detached and then exported during storms, constitute an important compartment in terms of organic matter transfer from the seagrass bed to the other ... [more ▼]

Decayed leaves of the Neptune grass Posidonia oceanica, detached and then exported during storms, constitute an important compartment in terms of organic matter transfer from the seagrass bed to the other habitats, particularly coastal habitats. These exported litter accumulations (ELA) support a diverse (more than 130 species) and abundant (up to 4900 id.m-2) vagile macrofauna (invertebrates > 500µm) assemblage which may play a key role in the degradation, enrichment and carbon transfer from P. oceanica dead material to coastal food chains. Indeed, preliminary results of vagile invertebrates gut content observations show that even if only a few of these species ingest a large proportion of P.oceanica dead leaves fragments, most of the others ingest a small but non-negligible part, suggesting a potential role of the whole community in the mechanical fragmentation of the dead leaves. ELA are very dynamic habitats with highly variable food availability, quality, and composition. Such an inconstant habitat may result in drastic modifications of the invertebrate community but also of its trophic structure and ecology. To test this hypothesis of influence of pulsed availability, quality and composition of food sources on the vagile macrofauna diet, we took seasonal samples in Calvi Bay (Corsica, 8°45’E; 42°35’N), at two sites between August 2011 and May 2012. Stable isotopes analysis (C&N) were conducted at an individual level on dominant macrofauna species and mixing and isotopic niche model packages in R were used. Bayesian inference “SIBER” package highlighted significant seasonal and spatial differences of diet at the community, specific and even intraspecific level. Data confirm the potential transfer of seagrass material to animal tissues but in various proportions depending of the species and the season. But one question remained: are these variations reflection a true diet change, or only a spatiotemporal baseline variation of the food sources isotopic composition? “SIAR” Bayesian mixing model showed that it depends on the species and that the two responses co-occur. We emphasized the need to work at the specific level but also with an adequate temporal resolution for sampling to encompass diet and baseline variability. [less ▲]

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See detailSeagrasses or caged mussels to bioassess the contamination rate of Mediterranean coastal waters? That is the question
Richir, Jonathan ULg; Galgani, François; Benedicto, José et al

in PeerJ (2015, May)

Biological indicators have the capacity to integrate the temporal changes of contaminants, concentrations or fluxes over various time-scales, and are thus considered as interesting tools for water quality ... [more ▼]

Biological indicators have the capacity to integrate the temporal changes of contaminants, concentrations or fluxes over various time-scales, and are thus considered as interesting tools for water quality biomonitoring. Since the mid-70ies, French programs have developed water monitoring approaches based on the use of bivalve molluscs; and recently the natural background and the extent of water contamination were bioassessed at the scale of the whole western Mediterranean. But even if bivalve molluscs are viewed as reliable bioindicators, their use is not always made easy as a result of their absence in numerous coastal regions that force their transplantation (cages) during several months before their sampling and analysis. This weakness led several scientists to evaluate the bioindicator abilities of other marine organisms. Seagrasses, whose ability to bioaccumulate contaminants proportionally to environmental contamination levels has been clearly demonstrated, have thus been proposed as an appropriate alternative tool for coastal water quality assessment. Very little studies have however so far considered the combined utilization of these two groups of bioindicator organisms, i.e. caged bivalve molluscs and seagrasses. In the framework of the STARECAPMED project, we therefore compared and discussed the bioaccumulation of trace elements in the Neptune grass Posidonia oceanica and in caged Mediterranean mussels Mytilus galloprovincialis. The sampling was performed at the scale of the western Mediterranean. The two species told two contamination stories which, although sometimes different, showed to be complementary. P. oceanica and M. galloprovincialis bioaccumulated dissolved trace elements from the water column and thus provided information regarding trace element contamination severity integrated over several days to a few months. Seagrasses, strongly rooted in the sediments, reflected the long-term exposure to trace elements since sediments offer a degree of time integration over several years to decades. Caged mussels, as filter feeder artificially maintained in the water column, bioaccumulated trace elements from their particulate phase, and therefore gave valuable information regarding continental-terrigenous inputs to coastal waters. In conclusion, seagrasses and mussels should neither supplant, nor substitute, but rather complement each other in order to provide the full time- and space-integrated coastal contamination story of the Mediterranean. [less ▲]

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See detailTrace element contamination severity of coastal waters: A first bioassessment at the scale of the whole Mediterranean Sea
Richir, Jonathan ULg; Salivas-Decaux, Maylis; Lafabrie, Céline et al

in PeerJ (2015, May)

Human activities generate large volumes of waste that supply marine coastal environments in pathogens, organic matter, nutrients and toxicants. Among the wide range of toxicants are trace elements. Since ... [more ▼]

Human activities generate large volumes of waste that supply marine coastal environments in pathogens, organic matter, nutrients and toxicants. Among the wide range of toxicants are trace elements. Since the latter are toxic for aquatic organisms from threshold levels and as they are therefore likely to cause multiple damage to the population, the community and the ecosystem levels, their environmental occurrence has to be accurately monitored in order to guarantee appropriate environmental management of coastal zones and to preserve marine coastal ecosystems and the goods and services they provide. In the framework of the STARECAPMED project, the present study aimed to monitor, for the first time, the coastal contamination of the entire Mediterranean by As, Ag, Cd, Cu, Hg, Ni and Pb, using Posidonia oceanica (L.) Delile as bioindicator species. But sustainable coastal management also requires the development of appropriate contamination classification systems intended, among other purposes, for environmental managers and policy makers. The combined utilization of several complementary monitoring tools, i.e. water quality scale, pollution index (TEPI and TESVI) and spatial analysis (PCA, CA, correlation analysis and GIS mapping) successfully led to the development of an operational classification system of this kind. In particular, the mapping of the trace element contamination according to a new proposed 5-level water quality scale using the quantile method precisely outlined the contamination severity along Mediterranean coasts and facilitated interregional comparisons. The reliability of the use of P. oceanica as bioindicator species was further again demonstrated through several global, regional and local detailed case studies. In conclusion, holistic approaches such as developed in the present study should be privileged to accurately monitor the contamination rate of coastal waters and to transfer relevant information on this composite problem to environmental managers and policy makers. [less ▲]

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See detailPatch types in Posidonia oceanica meadows around Corsica. How can we use them in seascape ecology?
Abadie, Arnaud ULg; Bonacorsi, Marina; Gobert, Sylvie ULg et al

Conference (2015, May)

The meadows formed by the Mediterranean seagrass Posidonia oceanica are subjected to various natural (e.g., water movement, light availability, sedimentation) and anthropogenic (e.g., anchoring, trawling ... [more ▼]

The meadows formed by the Mediterranean seagrass Posidonia oceanica are subjected to various natural (e.g., water movement, light availability, sedimentation) and anthropogenic (e.g., anchoring, trawling, fish farms, explosives) phenomena that erode them and create diverse types of patches. The assemblage of the P. oceanica matrix and these patches creates particular seascapes. On the basis of this assessment, we aimed to investigate the importance of the patch type in structuring P. oceanica seascapes and to offer new prospects in the large scale studies of seagrass meadows. Five sites encompassing large P. oceanica meadows ranging from 1.86 km² to 4.42 km² along the Corsican coast (France) were considered. Eleven patch types with different sizes, shapes and origins were identified using side scan sonar images (sonograms). Five were recognized as natural and five as anthropogenic. One can be of both origins. The resolution of the sonograms allowed to detect patches of various sizes ranging from 1 m² to 111 829 m². The relation between structural characteristics of patches and the whole seascape aspect was explored using seven landscape metrics relevant for the study of meadows patchiness (patch area, mean radius of gyration, area-weighted radius of gyration, coefficient of variation of the Euclidean nearest-neighbor distance, area-weighted perimeter-area ratio, landscape division index, number of patches). Only a small number of patch types appears to play the strongest role in the characterization of the P. oceanica seascapes. Furthermore, the use of seascape structures seems to be suitable for the development of new tools like indices for the assessment of human impacts on P. oceanica meadows. In this perspective we propose a new and simple index, the Patchiness Source Index (PaSI), to estimate the origin of the patchiness (natural or anthropogenic) for a given area. A landscape approach, as well as information on patch dynamic, should be integrated in the new indices that aim to assess the state of conservation of the whole P. oceanica ecosystem. [less ▲]

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See detailMapping Posidonia oceanica meadows through time A story of precision, evaluation and fragmentation
Abadie, Arnaud ULg; Jousseaume, Matthieu; Lejeune, Pierre et al

Poster (2015, May)

Over the last decades, the interest in mapping Posidonia oceanica beds has increased along with the improvement of the equipment’s precision of data acquisition. In Calvi Bay (Corsica, France) the meadows ... [more ▼]

Over the last decades, the interest in mapping Posidonia oceanica beds has increased along with the improvement of the equipment’s precision of data acquisition. In Calvi Bay (Corsica, France) the meadows cover an area of about 5 km² and are found at a depth ranging from 3 m to 37 m. The availability of three distinct datasets for 1997, 2002 and 2010 allowed to assess changes in the patchiness of the meadows in the bay and to investigate evolution of maps precision through a surface analysis via GIS software. Thus, three maps were elaborated combining aerial photographs and side scan sonar images. The meadows percentage of cover through time was assessed using four bathymetric sections: 0-10 m, 11-20 m, 21-30 m and 31-40 m. Differences in the patchiness of P. oceanica meadows between 1997 and 2010 appear to be moderate (less than 3 %) in the sections 0-10 m and 11-20 m and then greatly increase with depth: 24 % at 21-30 m and 39 % at 31-40 m. This amazing regression seems hardly natural and unlikely given the slight quantity of human activities that can cause damages on the P. oceanica meadows of the Calvi Bay. These results are likely to be mainly due to the improvement of precision and resolution of the aerial photographs (5 m in 1997, 0.8 m in 2002 and 0.5 m in 2010) and sonar images (5 m in 1997, 3 m in 2002 and 0.5 m in 2010). An issue of habitat determination (human vs instrumental) linked with the method adopted for mapping can also cause differences in the percentage of cover. Given the different accuracy among the three maps, the real regression and fragmentation of P. oceanica meadows could be hardly assessed. However, in several areas where the human activities are important, a clear regression or even a disappearance of the meadows has been observed. It is obvious that the last maps are more accurate than the previous ones and, thus, the former can be used for management purpose as well as for study on the patchiness; however, they still keep uncertainty no matter which method is used to create them. [less ▲]

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See detailApplication of stable isotopes in trophic ecology: importance of TEF and seasonal baseline for robust interpretations.
Remy, François ULg; Darchambeau, François ULg; Dauby, Patrick ULg et al

Conference (2015, April 02)

Nitrogen, carbon and sulfur stable isotopes are very powerful tools for trophic ecologists to delineate food webs of various ecosystems. More recently… the use of mixing models has exponentially increased ... [more ▼]

Nitrogen, carbon and sulfur stable isotopes are very powerful tools for trophic ecologists to delineate food webs of various ecosystems. More recently… the use of mixing models has exponentially increased to give a more specific vision of organism’s diets and trophic relationships. Two case studies will be presented to give a summary of what’s been done in Liège Oceanology Lab to improve our interpretation of stable isotopes results. First is an experimental calculation of the Trophic Enrichment Factors (TEFs) for one dominant detritivorous species of Mediterranean amphipod inhabiting seagrass detritus: Gammarus aequicauda (Martynov, 1931). This experimental study was planned after a strange result of the SAIR mixing model, giving results opposed to all observations and knowledge we had about this species. Thus, the impact of 3 very different food sources (amphipod powder, algae power, seagrass powder) on the turnover rate of C and N isotopic compositions was tested, and afterwards TEFs for C and N for each source were calculated. Animal food source showed to be the most effectively assimilated with a fast turnover rate while seagrass and algae showed very slow assimilation. TEFs calculations showed to be interesting because TEFs seem not to depend on the natural feeding type of the invertebrate but more on the type of food source. Animal source showed carnivorous TEFs values while seagrass and algae source showed typical detritivorous values. SIAR results with these new custom values gave more coherent values highlighting the major importance of TEFs values for mixing models data interpretation. Second is a simple question: are the seasonal isotopic composition variations observed for many seagrass detritus macrofauna species due to actual diet changes, or only to isotopic baseline shift of the food sources? Macrofauna and all potential food sources were sampled near STARESO Oceanographic Station (Corsica, 8°45’E; 42°35’N) in 2011-2012 at each season at two different sites. SIBER software runs with C and N isotopic data showed spatio-temporal isotopic variations at community, interspecific and intraspecific level. SIBER did not gave us information about the origin of these changes, but coupled with SIAR and our custom TEFs, species actually showing drastic changes of diet were identified, while others seem to reflect more a source baseline isotopic composition shift. Working at specific level is compulsory for fine conclusions. These two case studies highlight the importance of mixing model use and of accurate TEF values to run these models properly to draw robust and reliable conclusions using stable isotopic data. [less ▲]

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See detailApplications of stable isotopes in environmental studies at the University of Liege
Sturaro, Nicolas ULg; Borges, Alberto ULg; Das, Krishna ULg et al

Poster (2015, March 26)

Measurement and use of stable isotope ratios have a long history at the University of Liege (Belgium). Since at least 30 years, applications of stable isotopes in marine ecosystems have been developed ... [more ▼]

Measurement and use of stable isotope ratios have a long history at the University of Liege (Belgium). Since at least 30 years, applications of stable isotopes in marine ecosystems have been developed within the Laboratory of Oceanology and, more recently, within the Chemical Oceanography Unit. In the Laboratory of Oceanology, one research axis is the measurement of stable isotope composition (C, N, S) in organic matter to delineate trophic web structure and to study animal diet, their trophic niches and their alteration by human activities. This methodology has been successively applied worldwide in different habitats and ecosystems (marine, freshwater, terrestrial) in temperate and tropical areas. Mediterranean food web and fish trophic ecology have received a particular attention. Coupling between trophic ecology and ecotoxicology is another area of investigation. This has been applied mainly to marine vertebrates and freshwater ecosystems. Stable isotope labelling is also used in our laboratory to study and quantify various ecological processes such as inorganic nitrogen incorporation and trophic transfers. The laboratory facilities, renewed in 2012 and managed by Dr. Gilles Lepoint, are composed of an elemental analyser (EA, vario MICRO cube, Elementar) and a gas chromatography (GC, Agilent) coupled to an isotope ratio mass spectrometer (IRMS, Isoprime 100). The GC is also equipped with a quadrupole mass spectrometer. In 2014, the Chemical Oceanography Unit, headed by Dr. Alberto Borges, has acquired and implemented an off-axis cavity ring-down spectroscopy (CRDS) for the measurements of δ15Nα, δ15Nβ, δ18O of N2O. This enables characterization of the N2O origin in a variety of aquatic environments including groundwater in Wallonia, rivers and lakes in Wallonia and Africa, coastal environments (Scheldt estuary, Lake Grevelingen, North Sea), Mediterranean seagrass beds, and Antarctic and Arctic sea-ice. [less ▲]

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Peer Reviewed
See detailBioassessment of trace element contamination of Mediterranean coastal waters using the seagrass Posidonia oceanica
Richir, Jonathan ULg; Salivas-Decaux, Maÿlis; Lafabrie, Céline et al

in Journal of Environmental Management (2015), 150

A large scale survey of the trace element (TE) contamination of Mediterranean coastal waters was performed from the analysis of Ag, As, Cd, Cu, Hg, Ni and Pb in the bioindicator Posidonia oceanica ... [more ▼]

A large scale survey of the trace element (TE) contamination of Mediterranean coastal waters was performed from the analysis of Ag, As, Cd, Cu, Hg, Ni and Pb in the bioindicator Posidonia oceanica, sampled at 110 sites differing by their levels of exposure to contaminants. The holistic approach developed in this study, based on the combined utilization of several complementary monitoring tools, i.e. water quality scale, pollution index and spatial analysis, accurately assessed the TE contamination rate of Mediterranean coastal waters. In particular, the mapping of the TE contamination according to a new proposed 5-level water quality scale precisely outlined the contamination severity along Mediterranean coasts and facilitated interregional comparisons. Finally, the reliability of the use of P. oceanica as bioindicator species was again demonstrated through several global, regional and local detailed case studies. NB: The designations employed and the presentation of the information in thisdocument do not imply the expression of any opinion whatsoever on the part of the authors concerning the legal status of any country, territory, city or area or of its authorities, or concerning the delimitation of its frontiers or boundaries. [less ▲]

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See detailEarly colonization on Artificial Seagrass Units and on Posidonia oceanica (L.) Delile leaves
Pete, Dorothée ULg; Lepoint, Gilles ULg; Bouquegneau, Jean-Marie ULg et al

in Belgian Journal of Zoology (2015), 145(1), 59-68

Many epiphytes grow on Posidonia oceanica (L.) Delile leaves but early stages of that colonization are not well known. To study this early colonization without destroying the plant, Artificial Seagrass ... [more ▼]

Many epiphytes grow on Posidonia oceanica (L.) Delile leaves but early stages of that colonization are not well known. To study this early colonization without destroying the plant, Artificial Seagrass Units (ASUs) were utilised. The first nine days of colonization by macroscopic eukaryotic organisms on natural P. oceanica leaves and on ASUs were studied. The capability of those ASUs to mimic P. oceanica in the long term was also evaluated. Indeed, early colonists of a substrate can influence the settling of later ones by “priority effects”. Thus if the pioneer community is the same on both substrates, they will more likely be the same after a longer exposure time. On both substrates, colonization began by the settling of crustose-calcareous algae and foraminiferans. The number of organisms increased more quickly on ASUs than on natural leaves but Shannon-Wiener diversity index was higher for P. oceanica leaves. The low colonization rate on natural leaves may have been due to different microclimatic conditions on the two substrates and to a less developed biofilm than on ASUs. The high diversity observed on natural leaves was mainly related to the presence of bryozoan ancestrulae, which were absent on ASUs. Different microhabitats on each substrate (different algae morphotypes) can explain this difference. Thus, at such an early colonization stage, pioneer communities were different on the two substrates, suggesting that later communities would be different too. However, ASUs could be used in environmental perturbation studies instead of natural leaves, thanks to their high colonization rate. [less ▲]

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See detailMarine space ecology and seagrasses. Does patch type matter in Posidonia oceanica seascapes?
Abadie, Arnaud ULg; Gobert, Sylvie ULg; Bonacorsi, Marina et al

in Ecological Indicators (2015), 57

The use of landscape tools in the study of seagrass meadows (seascapes) begins to be widely spreadbut still require the establishment of several basis, i.e. a patch type classification based on ... [more ▼]

The use of landscape tools in the study of seagrass meadows (seascapes) begins to be widely spreadbut still require the establishment of several basis, i.e. a patch type classification based on numericalcharacteristics. Thanks to the complex seascapes created by the Posidonia oceanica meadows, they appearto be suitable for a study at a patch type level (class), which bring a new insight of their arrangement at thewhole seascape scale. By interpreting side scan sonar images from the Corsican coast (France) through aGIS software, it was possible to describe 11 types of patches and to evaluate their natural or anthropogenicorigin. Comparison of different landscape metrics and wave exposure (Relative wave Exposure Index,REI) at the seascape and the patch level showed that the particularity of P. oceanica seascapes are mainlycharacterized by certain types of patches often of anthropogenic origin. Furthermore the REI seems not tobe a relevant index for a study at a class scale. A bathymetrical succession of natural patches was outlinedfrom the lower to the upper limit of the meadow, with a long-term dynamic opposed to a shorter oneconcerning anthropogenic patches. In order to assess the origin (natural or induced by human activities)of the patches in P. oceanica meadows, as well as in any other seagrass, a Patchiness Source Index (PaSI),ranging from 0 to 1, was defined. [less ▲]

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See detailTowards a framework for assessment and management of cumulative human impacts on marine food webs
Giakoumi, Sylvaine; Halpern, Benjamin S.; Michel, Loïc ULg et al

in Conservation Biology (2015), 29(4), 1228-1234

Effective ecosystem-based management requires understanding ecosystem responses to multiple human threats, rather than focusing on single threats. To understand ecosystem responses to anthropogenic ... [more ▼]

Effective ecosystem-based management requires understanding ecosystem responses to multiple human threats, rather than focusing on single threats. To understand ecosystem responses to anthropogenic threats holistically, it is necessary to know how threats affect different components within ecosystems and ultimately alter ecosystem functioning. We used a case study of a Mediterranean seagrass (Posidonia oceanica) food web and expert knowledge elicitation in an application of the initial steps of a framework for assessment of cumulative human impacts on food webs. We produced a conceptual seagrass food web model, determined the main trophic relationships, identified the main threats to the food web components, and assessed the components’ vulnerability to those threats. Some threats had high (e.g., coastal infrastructure) or low impacts (e.g., agricultural runoff) on all food web components, whereas others (e.g., introduced carnivores) had very different impacts on each component. Partitioning the ecosystem into its components enabled us to identify threats previously overlooked and to reevaluate the importance of threats commonly perceived as major. By incorporating this understanding of system vulnerability with data on changes in the state of each threat (e.g., decreasing domestic pollution and increasing fishing) into a food web model, managers may be better able to estimate and predict cumulative human impacts on ecosystems and to prioritize conservation actions. [less ▲]

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