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See detailEarly colonization of Posidonia oceanica (L.) Delile by epiphytes: Comparison between natural and artificial seagrass leaves
Pete, Dorothée ULg; Gobert, Sylvie ULg; Lepoint, Gilles ULg et al

in Pergent-Martini, Christine; El Asmi, Souha; Le Ravallec, Célia (Eds.) Proceedings of the third Mediterranean symposium on marine vegetation (2007, March)

Posidonia oceanica is an important marine Magnoliophyta of the Mediterranean coastal zone that can form dense meadows. The leaves of this seagrass are colonized by a lot of organisms, from bacteria to ... [more ▼]

Posidonia oceanica is an important marine Magnoliophyta of the Mediterranean coastal zone that can form dense meadows. The leaves of this seagrass are colonized by a lot of organisms, from bacteria to polychaetes and algae. However, the early stages of colonization are not well known. A preliminary is proposed to examine the nine first days of colonization by epiphytes on natural leaves and on Artificial Seagrass Units (ASUs). Aims of this work were to understand which species are the first to set up, to compare colonization on both leaves and to determine the interest of ASUs in ecological studies. It was shown that the setting up of epiphytes on the bases of both leaves is rapid (first algae on the second day) but the number of organisms increases quicker on ASUs than on natural leaves and on the smooth faces than the rough ones. Shannon-Wiener diversity and evenness were higher for the P. oceanica leaves and the use of Bray-Curtis similarity index showed that colonisation is not similar (between 20 and 30 % similarity) on both leaves for the same day. It can be explained by the lower colonization rate of natural leaves. This lower rate is probably due to a less developed biofilm on natural leaves than on ASUs, to a difficult access to the bases of P. oceanica leaves for epiphytes and microoganisms, and the production of phenol compounds by the plant. Even if ASUs used here do not seem to be similar to natural leaves in early stages of colonization, they could be used in ecological studies thanks to their rapid covering by epiphytes. [less ▲]

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See detailUse of exergy to detect and measure perturbations affecting Posidonia oceanica (L.) Delile meadows: Characterization in the sedimentary compartment
Pete, Dorothée ULg; Bouquegneau, Jean-Marie ULg; Gobert, Sylvie ULg

Poster (2007, March)

Within the scope of the European Water Framework Directive, it seems important to characterize state and evolution of marine ecosystems in a global way. So, it is proposed to use both thermodynamic ... [more ▼]

Within the scope of the European Water Framework Directive, it seems important to characterize state and evolution of marine ecosystems in a global way. So, it is proposed to use both thermodynamic indicators called exergy (Ex) and specific exergy (Exsp) in Posidonia oceanica meadows. Aims of this project are to detect and measure perturbations owed to nutrients loading and mechanical spoiling in the Mediterranean coastal zone. It will be led in the Bay of Calvi, on the microbenthic loop (organic matter, bacteria, microphytobenthos and meiofauna) and will be divided in two parts: sampling in different zone of the meadow and in situ experiments. In the end of this study, it will be possible to give a diagnostic on the health of P. oceanica meadow and to determine how this health will evolve, thanks to the introduction of the exergy in a model. [less ▲]

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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 detailVIABILITY OF THE NORTHEAST ATLANTIC HARBOUR PORPOISE AND SEAL POPULATION (GENETIC AND ECOLOGICAL STUDY)
Das, Krishna ULg; Drouguet, Olivier; Fontaine, Michaël ULg et al

Report (2007)

Harbour porpoises (Phocoena phocoena) and harbour seals (Phoca vitulina) are far more abundant along our coast compared to the beginning of the nineties. Human impact on these species is however hard to ... [more ▼]

Harbour porpoises (Phocoena phocoena) and harbour seals (Phoca vitulina) are far more abundant along our coast compared to the beginning of the nineties. Human impact on these species is however hard to establish, mainly due to lack of information on marine mammal population ecology, density, distribution and diversity. This project aims to gain further knowledge on the viability of the harbour porpoise and harbour seal populations in the North Sea (focusing mainly on its southern Bight) through - The characterisation of their genetic structure and diversity (through mtDNA and microsatellites in harbour porpoises) - A better understanding of their feeding ecology (through δ13C and δ15N measurements in muscles) - The assessment of their susceptibility of being trapped accidentally in fishing nets (post-mortem investigations) Harbour porpoise and harbour seal occupied the top trophic levels but displayed different feeding habits as inferred from their δ13C and δ15N mean values. Harbour porpoises displayed lower mean δ15N values suggesting a lower trophic position likely oriented towards small planktivorous fish such as herring and lesser sandeel. However, both their recent high abundance and their dietary preferences might lead to a higher susceptibility to by-catch as revealed by the significant emergence of net entrapment and net marks revealed by post-mortem investigations. The question rises about the sustainability of these incidental captures. Furthermore, genetic investigations revealed a higher fragmentation of the porpoises collected along the coast of France, Belgium and Netherlands. This apparent fragmentation is of particular importance from a conservation point of view and enhances the fact to protect in priority these last populations. Our study showed importance of multidisciplinary approaches (post-mortem investigations, stable isotope measurements (δ13C and δ15N measurements) and genetic investigations using mtDNA and microsatellites) to apprehend the question of marine mammal survival in our waters. [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 detailZn, Cu, Cd and Hg Binding to Metallothioneins in Harbour Porpoises Phocoena Phocoena from the Southern North Sea
Das, Krishna ULg; De Groof, Arnaud; Jauniaux, Thierry ULg et al

in BMC Ecology (2006), 6

BACKGROUND: Harbour porpoises Phocoena phocoena from the southern North Sea are known to display high levels of Zn and Hg in their tissues linked to their nutritional status (emaciation). The question ... [more ▼]

BACKGROUND: Harbour porpoises Phocoena phocoena from the southern North Sea are known to display high levels of Zn and Hg in their tissues linked to their nutritional status (emaciation). The question arises regarding a potential role of metallothioneins (MTs) with regard to these high metal levels. In the present study, metallothionein detection and associated Zn, Cd, Cu and Hg concentrations were investigated in the liver and kidney of 14 harbour porpoises collected along the Belgian coast. RESULTS: Metallothioneins seemed to play a key role in essential metal homeostasis, as they were shown to bind 50% of the total hepatic Zn and 36% of the total hepatic Cu concentrations. Renal MTs also participated in Cd detoxification, as they were shown to bind 56% of the total renal Cd. Hg was mainly found in the insoluble fraction of both liver and kidney. Concomitant increases in total Zn concentration and Zn bound to MTs were observed in the liver, whereas Zn concentration bound to high molecular weight proteins remained constant. Cu, Zn and Cd were accumulated preferentially in the MT fraction and their content in this fraction increased with the amount in the hepatocytosol. CONCLUSION: MTs have a key role in Zn and Cu homeostasis in harbour porpoises. We demonstrated that increasing hepatic Zn concentration led to an increase in Zn linked to MTs, suggesting that these small proteins take over the Zn overload linked to the poor body condition of debilitated harbour porpoises. [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 detailFeeding ecology of five commercial shark species of the Celtic Sea through stable isotope and trace metal analysis
Domi, Nadège; Bouquegneau, Jean-Marie ULg; Das, Krishna ULg

in Marine Environmental Research (2005), 60(5),

In order to trace their feeding habits, stable carbon and nitrogen isotope ratios (delta(15)N and delta(13)C), as well as trace metal concentrations (Zn, Cd, Fe, Cu, Se and Hg) were analysed in the ... [more ▼]

In order to trace their feeding habits, stable carbon and nitrogen isotope ratios (delta(15)N and delta(13)C), as well as trace metal concentrations (Zn, Cd, Fe, Cu, Se and Hg) were analysed in the tissues of five commercial shark species from the Celtic Sea: the tope shark Galeorhinus galeus, the black-mouthed catshark Galeus melastomus, the starry smooth hound Mustelus asterias, the spiny dogfish Squalus acanthias and the lesser-spotted dogfish Scyliorhinus canicula. Our results were compared to previously described stomach contents and isotopic composition of potential preys. Isotopic ratio delta(15)N suggested that tope sharks fed at a higher trophic level (16.7 parts per thousand in the muscle) than the other species, reflecting its piscivorous diet. The lower values of spiny dogfish (11.6 parts per thousand in the muscle) might be explained, amongst other things, by either its migratory behaviour or its preference for preys from lower trophic levels. Cd and Hg were correlated with isotopic ratios delta(13)C and delta(15)N, and were shown to be diet-related whereas Zn, Fe and Cu seemed much more linked to species-specific metabolism. Although this multidisciplinary approach is revealed as a useful tool for the study of shark ecology, the lack of known trophic fractionation suggests that isotopic data be compared to traditional diet analyses. (c) 2005 Elsevier Ltd. All rights reserved. [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 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 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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