References of "Bouquegneau, Jean-Marie"
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See detailDistribution and accumulation pattern of perfluorooctane sulfonic acid (PFOs) in marine mammals from the North Sea
Van de Vijver, Kristin; Das, Krishna ULg; Van Dongen, W. et al

Poster (2002, November)

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See detailExperimental evidence for N recycling in the leaves of the seagrass Posidonia oceanica
Lepoint, Gilles ULg; Defawe, Olivier; Gobert, Sylvie ULg et al

in Journal of Sea Research (2002), 48(3), 173-179

A one-year in situ experiment using N-15 as a tracer was designed to assess the N recycling in the leaves of the seagrass Posidonia oceanica (L.) Delile. R oceanica was shown to partly recycle the ... [more ▼]

A one-year in situ experiment using N-15 as a tracer was designed to assess the N recycling in the leaves of the seagrass Posidonia oceanica (L.) Delile. R oceanica was shown to partly recycle the internal nitrogen pool of its leaves in order to contribute to new leaf growth. The leaves sampled in June 1999 contained 20% of the quantity of N-15 found in June 1998. N recycling caused a difference between N and biomass turnover rate (0.8 vs 1.3 y(-1)) of Posidonia leaves. This 40% difference should correspond to the contribution of recycled N to the annual N requirement of Posidonia leaves. The N recycling appears to be insufficient to significantly reduce the quantitative impact of N loss due to autumnal leaf fall. However, new leaf growth between June and October is mainly sustained by this recycling because the tracer concentration in new leaves was the same as in the other leaves. By contrast, tracer concentration decreased drastically between October 1998 and June 1999, showing the more important contribution of N uptake during winter and spring. Nevertheless, recycling occurs throughout the year as demonstrated by the presence of tracer in the youngest leaves of shoots sampled one year after the tracer addition. (C) 2002 Elsevier Science B.V. All rights reserved. [less ▲]

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See detailDetermination of organohalogenated contaminants in liver of harbour porpoises (Phocoena phocoena) stranded on the Belgian North Sea coast
Covaci, Adrian; Van de Vijver, Kristin Inneke; De Coen, Wim et al

in Marine Pollution Bulletin (2002), 44(10),

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See detailAnnual nitrogen budget of the seagrass Posidonia oceanica as determined by in situ uptake experiments
Lepoint, Gilles ULg; Millet, S.; Dauby, Patrick ULg et al

in Marine Ecology. Progress Series (2002), 237

The uptake of nitrate and ammonium by the roots and leaves of Posidonia oceanica were determined between February 1993 and June 1999 by in situ experiments using the isotope 15 of nitrogen (N-15) as a ... [more ▼]

The uptake of nitrate and ammonium by the roots and leaves of Posidonia oceanica were determined between February 1993 and June 1999 by in situ experiments using the isotope 15 of nitrogen (N-15) as a tracer in a nutrient-poor coastal zone of the NW Mediterranean Sea (Revellata Bay, Corsica). Nitrate and ammonium leaf uptakes are recorded at 0.05 and 0.1 muM respectively. The high variability observed cannot be explained solely by the variation of the substrate concentrations in the water column. For leaves, mean specific uptake rates were 43 +/- 45 and 43 +/- 64 mug N g N-1 h(-1). Nitrate and ammonium leaf uptake fluxes (g N m(-2) yr(-1)) seem to have the same importance on an annual basis. :Nitrate uptake occurs mainly in winter and early spring, when nitrate concentrations in the water column are highest. The uptake of N, and mainly of ammonium, is significant throughout the year with maxima at the beginning of spring, but it is insufficient to meet the annual N requirement of the plant. Posidonia root biomass was very high and corresponded to high specific N uptake rates by the roots. Ammonium was incorporated by the roots 6 times faster than nitrate. In the sediment, this uptake capacity is limited by the nutrient diffusion rate, and the root uptake is therefore insufficient to meet the N requirements of the plant. In fact, P. oceanica of Revellata Bay have a complex N budget involving uptake and recycling processes and allowing the plants to meet their N requirements in one of the most nutrient-poor areas of the NW Mediterranean Sea. We calculated that leaf and root would contribute to 40 and 60% of the annual N uptake, respectively, and 60% of the annual N requirement of the plant. [less ▲]

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See detailMarine mammal selenium linked mercury detoxifaction processes
Holsbeek, Ludo; Das, Krishna ULg; Bouquegneau, Jean-Marie ULg et al

Poster (2002, May 13)

New results confirm earlier findings on the importance of tiemannite acumulation on speciation and inter-tissue relationships. It is hardly surprising that, as opposed to what was concluded earlier, major ... [more ▼]

New results confirm earlier findings on the importance of tiemannite acumulation on speciation and inter-tissue relationships. It is hardly surprising that, as opposed to what was concluded earlier, major inter-regional differences in Hg accumulation can be demonstrated when comparing several populations of harbour porpoise on an age corrected basis. Important inter-species differences, probably depending on prey choice, are found, even after correction for "relative age". Regional differences are more important than the inter-species variability, at least within both classically described sub-orders of cetaceans. Based on actual estimates of MeHg exposure and tissue concentrations of Hg and MeHg in harbour porpoise from the Southern North Sea, Hg detoxification through precipitation of tiemannite is evaluated to neutralise on average 12% of the overall MeHg intake at age 7. Based on the idea of a 3 fold excess in toxicity of mercury over selenium and a 5 to 15 molar concentration excess of selenium over Hg in fish, Hg seems to play the major part in the mutual detoxification. The formation of tiemannite was previously described as resulting from a two-step accumulation mechanism appearing at a threshold level of Hg 100 g/g fw in liver. The reaching of an equimolar Hg to Se ratio can, however, be fully explained by the gradual increase of tiemannite levels in liver only. The new view is that molar Hg to Se hepatic ratios go towards equimolarity along with the slow nature of the tiemannite detoxification process, with tiemannite gradually taking the upper hand over MeHg, IHg2+ and a surplus of "free" selenium with the increase of the total Hg load. [less ▲]

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See detailRelative trophic levels of several marine mammal species from the Northwestern Atlantic determined through stable isotope analyses
Beans, Christina; Das, Krishna ULg; Mauger, Gérard et al

Poster (2002, April)

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See detailPosidonia Oceanica Meadow: A Low Nutrient High Chlorophyll (LNHC) System?
Gobert, Sylvie ULg; Laumont, N.; Bouquegneau, Jean-Marie ULg

in BMC Ecology (2002), 2

BACKGROUND: In spite of very low nutrient concentrations in its vicinity - both column and pore waters-, the Posidonia oceanica of the Revellata Bay displays high biomass and productivity. We measured the ... [more ▼]

BACKGROUND: In spite of very low nutrient concentrations in its vicinity - both column and pore waters-, the Posidonia oceanica of the Revellata Bay displays high biomass and productivity. We measured the nutrient fluxes from the sediment into the water enclosed among the leaf shoots ("canopy water") to determine if it is possible source of nutrients for P. oceanica leaves. RESULTS: During the summer, the canopy water appears to act as a nutrient reservoir for the plant. During that period, the canopy water layer displays both a temperature 0.5 degrees C cooler than the upper water column, and a much higher nutrient content, as shown in this work using a very simple original technique permitting to sample water with a minimal disturbance of the water column's vertical structure.Despite low nutrient concentrations in pore water, mean net fluxes were measured from the sediment to the canopy water. These fluxes are sufficient to provide 20% of the mean daily nitrogen and phosphorus requirement of the P. oceanica shoots. CONCLUSION: An internal cycling of nutrients from P. oceanica senescent leaves was previously noted as an efficient strategy to help face low nutrient availability. The present study points out a second strategy which consists in holding back, in the canopy, the nutrients released at the water-sediment interface. This process occurs when long leaves, during poor nutrient periods in the water column, providing, to P. oceanica, the possibility to develop, high biomass, high chlorophyll quantities in low nutrient environment (a Low Nutrients High Chlorophyll system). [less ▲]

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See detailWhite-sided dolphin metallothioneins: purification, characterisation and potential role
Das, Krishna ULg; Jacob, Valérie; Bouquegneau, Jean-Marie ULg

in Comparative Biochemistry & Physiology Part C : Toxicology & Pharmacology (2002), 131(3),

Metallothioneins (MTs) were characterised in the kidneys of a white-sided dolphin Lagenorhynchus acutus stranded along the Belgian coast, displaying high levels of cadmium (Cd) and mercury (Hg) in liver ... [more ▼]

Metallothioneins (MTs) were characterised in the kidneys of a white-sided dolphin Lagenorhynchus acutus stranded along the Belgian coast, displaying high levels of cadmium (Cd) and mercury (Hg) in liver and kidney. The protein has two isoforms: MT-1 and MT-2. MT-1 binds Cu, Zn, Hg and Cd, while MT-2 only binds Zn, Hg and Cd. This suggests different metabolic functions for the two isoforms: MT-1 is mainly involved in Cu homeostasis; MT-2, which was fourfold more abundant than MT-1, detoxifies most of the accumulated cadmium. (C) 2002 Elsevier Science Inc. All rights reserved. [less ▲]

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See detailNew findings on selenium related mercury detoxification processes.
Holsbeek, Ludo; Das, Krishna ULg; Bouquegneau, Jean-Marie ULg et al

Poster (2002)

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See detailSources of variation of trace metals of harbour porpoise (Phocoena phocoena) by caught from Norwegian waters.
Fontaine, Michaël; Das, Krishna ULg; Siebert, Ursula et al

Poster (2002)

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See detailInfluence of Age, Sex and Body Condition on Zinc, Copper, Cadmium and Metallothioneins in Common Guillemots (Uria aalge) Stranded at the Belgian Coast.
Debacker, Virginie ULg; Schiettecatte, Laure-Sophie; Jauniaux, Thierry ULg et al

in Marine Environmental Research (2001), 52(5), 427-444

The common guillemots, Uria aalge, found stranded at the Belgian coast, display high levels of Cu in both liver and kidneys. The condition index of the animals, defined as the ratio of liver to kidneys ... [more ▼]

The common guillemots, Uria aalge, found stranded at the Belgian coast, display high levels of Cu in both liver and kidneys. The condition index of the animals, defined as the ratio of liver to kidneys mass (Wenzel & Adelung, 1996), influences both the metal concentration and its binding to metallothioneins (MT): the lower the condition index, the more emaciated the animals, and the higher the total Cu concentration and the concentration of Cu bound to MT. In less robust individuals, our results suggest that Cu could displaces Zn from MT rendering the Zn ions available to induce a new MT synthesis. Sex related effects also emerged as significantly higher hepatic MT as well as Cu- and Zn-MT concentrations were found in emaciated male guillemots compared to females. In both organs, Cd concentrations remained low and typically demonstrated an age-dependent renal accumulation, with no noticeable effect of the condition index. As a whole, these results suggest that, for guillemots found stranded at the Belgian coast, Cu binding to hepatic and renal MT could function as a protective mechanism, rendering the metal ions unavailable to exert any cytotoxic activity. [less ▲]

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See detailThe role of benthic amphipods in the eastern Weddell Sea trophic web as determined from stable isotope and fatty acid analyses
Nyssen, Fabienne ULg; Brey, Thomas; Graeve, Martin et al

Conference (2001, August)

Within the Southern Ocean, amphipods have achieved a conspicuous adaptative radiation which gave rise to the development of numerous feeding strategies (Jazdzewski et al. 1996; Dauby et al. in press; De ... [more ▼]

Within the Southern Ocean, amphipods have achieved a conspicuous adaptative radiation which gave rise to the development of numerous feeding strategies (Jazdzewski et al. 1996; Dauby et al. in press; De Broyer et al. in press). The discrepancy between the ecological significance of amphipods in the Antarctic and our poor knowledge of their ecofunctional role calls for a more detailed investigation of their importance in this ecosystem trophodynamics. This study focused on the eight amphipods species which were collected and from which isotopic and lipidic (when available) (Graeve et al. in press) compositions were compared to their respective gut contents previously described (Dauby et al. in press). The interest of both first techniques rely upon the direct relationship between the isotopic signatures and the lipid composition of organisms and those of their diet (De Niro and Epstein 1978, 1981; Peterson and Fry 1987; Graeve et al. 1994; Cripps et al 1999). Amphipod stable isotope ratios and fatty acids composition correspond rather accurately to the trophic classification based on gut contents and attest to their high spectrum of feeding types. Since the fundamental difference between the approaches to diet studies is the time scale each method addresses, this coincidence indicates that there would be no significant changes in feeding strategies over time. Three levels of the food web are covered by the eight species and, instead of belonging strictly to one trophic category, amphipods display a continuum of values from the suspension-feeder to scavengers. [less ▲]

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See detailSurvey of health status of a P oceanica meadow since 1975: perfecting of a method for the meadow rehabilitation and restoration
Gobert, Sylvie ULg; Vangeluwe, Denis; Lepoint, Gilles ULg et al

in Proceeding of the 5th meeting of the European Platform for Biodiversity Research Strategy (2001)

A long-term survey of the P. oceanica meadow has been in progress since 1975 in the Revallata Bay (Corsica, France) (e.g.Bay, 1984). Actually, since 1991, biometric parameters of the meadow have been ... [more ▼]

A long-term survey of the P. oceanica meadow has been in progress since 1975 in the Revallata Bay (Corsica, France) (e.g.Bay, 1984). Actually, since 1991, biometric parameters of the meadow have been monitored regularly (Gobert et al., 1995). The seasonal, interannual and long term changes of these Posidonia characteristics are analysed regarding meteorological (e.g.sun, rain, temperature..)and anthropologic events such as tourism and nutrient enriched effluents in the area. Our results have pointed out the good health status of the meadow in spite of some ecological modifications linked to the increasing water temperature (Gobert et al., in press). Recent aerial photos have shown a modification of the covering surface of the meadow. An accurate studyof causes of the distribution modifications is beginning. Using our long term background data on the meadow, we are developing a transplantation technique of P. oceanica shoots using semi-artificial substrates (EAT:electrochemical accretion technology) (Van Treeck and Schuhmacher, 1998) with the aim of providing a guideline-report based on model case studies representative for many threatened Mediterranean areas. [less ▲]

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See detailAnthesis effects on Posidonia oceanica (L.) Delile phenology in the Bay of Calvi (Corsica, Mediterranean Sea)
Gobert, Sylvie ULg; Defawe, Olivier; Lepoint, Gilles ULg et al

in Hydrobiologia (2001), 455

In Posidonia oceanica (L.) Delile, anthesis induces a decrease in the number of juvenile leaves resulting in a significant reduction in the number of leaves on the flowering shoots. All the leaves of the ... [more ▼]

In Posidonia oceanica (L.) Delile, anthesis induces a decrease in the number of juvenile leaves resulting in a significant reduction in the number of leaves on the flowering shoots. All the leaves of the flowering shoots are narrower than the leaves of nonflowering shoots. A modification of the leaf growth also appears in flowering shoots: the oldest leaves are longer and the leaves induced during or after anthesis are shorter. At 10 m depth, in the Bay of Calvi, anthesis lasts roughly 3 months and the flowering is induced 7 months before anthesis. [less ▲]

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See detailMarine mammals from the North Sea: Insights in their feeding ecology and nutritional status from stable isotopes ratio and heavy metal concentrations
Das, Krishna ULg; Jauniaux, Thierry ULg; Holsbeek, Ludo et al

Poster (2001)

The relationship between trace metal levels, trophic position and health status has been investigated in North Sea marine mammals. Stable isotope ratio (15N and 13C, mass spectrometry) and trace metal ... [more ▼]

The relationship between trace metal levels, trophic position and health status has been investigated in North Sea marine mammals. Stable isotope ratio (15N and 13C, mass spectrometry) and trace metal analyses (Cd, Pb, Cu, Zn, Se, Hg, I.C.P Spectrometry and flameless atomic absorption) have been performed in tissues of 52 harbour porpoises Phocoena phocoena, 27 harbour seals Phoca vitulina, 9 white-beaked dolphins Lagenorhynchus albirostris, 6 grey seals Halichoerus grypus, 1 hooded seal Cystophora cristata, 2 white-sided dolphin Lagenorhynchus acutus, 7 sperm whales Physeter macrocephalus and 4 fin whales Balaenoptera physalus, found stranded on the Northern French, Belgian and Southern Dutch coasts. The lowest 15N value has been measured in fin whales, and the highest in white-beaked dolphins, grey and common seals, suggesting a higher trophic position. Sperm whales, white-sided dolphins and hooded seal have strongly negative 13C values and high renal cadmium levels (258, 88 and 62 µg Cd .g-1dw, respectively) indicating that they might feed, at least in part, on oceanic cephalopods. High Hg liver concentrations can be encountered in older animals and reflect a cumulative storage of detoxified HgSe over the whole life span rather than a bioamplification process. Zn, Cu and Hg concentrations were higher in harbour porpoises from the Southern North Sea compared to other areas. Some individuals were severely emaciated as shown by their muscle atrophy and reduced blubber thickness. Hepatic Zn and Se concentrations were significantly higher in emaciated juvenile porpoises than in normal animals suggesting a severe disturbance of the metal homeostasis. To conclude, within the North Sea, trace metal levels in marine mammals display strong intra- and interspecies variations due to geographic origin, age, diet, trophic position but also by nutritional status of the individuals, raising the question of the suitability of marine mammals as valuable bioindicators of trace metal pollution. [less ▲]

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See detailA stable isotope approach to the eastern Weddell Sea trophic web: focus on benthic amphipods
Nyssen, Fabienne ULg; Brey, Thomas; Lepoint, Gilles ULg et al

in Polar Biology (2001), 25(4),

isotope (C-13/C-12 and N-15/N-14) analyses were performed on 90 species belonging to different benthic communities sampled in the eastern Weddell Sea. The study focused on eight amphipod species whose ... [more ▼]

isotope (C-13/C-12 and N-15/N-14) analyses were performed on 90 species belonging to different benthic communities sampled in the eastern Weddell Sea. The study focused on eight amphipod species whose isotopic composition was compared to their previously described respective gut contents. Amphipod stable isotope ratios correspond fairly accurately to the trophic classification based on gut contents and attest to their wide spectrum of feeding types. Since the fundamental difference between the isotope and the gut content approaches to diet studies is the time scale each method addresses. this coincidence indicates that there would be no significant changes in feeding strategies over time. Three levels of the food web are covered by the eight species and, instead of belonging strictly to one trophic category, amphipods display a continuum of values from the suspension-feeder to scavengers. [less ▲]

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See detailCombined Effects of Experimental Heavy-Metal Contamination (Cu, Zn, and CH3Hg) and Starvation on Quail's Body Condition: Parallelism with a Wild Common Guillemot (Uria aalge) Population Found Stranded at the Belgian Coast
Debacker, Virginie ULg; Rutten, Astrid; Jauniaux, Thierry ULg et al

in Biological Trace Element Research (2001), 82(1-3, Summer), 87-107

Combined effects of heavy-metal contamination (Cu, Zn, and CH3Hg) and starvation were tested on common quails (Coturnix coturnix japonica) and used as a model for comparison with a wild common guillemot ... [more ▼]

Combined effects of heavy-metal contamination (Cu, Zn, and CH3Hg) and starvation were tested on common quails (Coturnix coturnix japonica) and used as a model for comparison with a wild common guillemot (Uria aalge) population found stranded at the Belgian coast. Appropriate heavy-metal levels were given to the quails to obtain concentrations similar to those found in the seabirds's tissues. The contaminated animals were then starved for 4 d to simulate the evident malnutrition symptoms observed at the guillemot's level. In such conditions, food intake and total-body weight are shown to decrease in contaminated individuals with simultaneous significant hepatic and renal increase of the heavy-metal concentrations. Like guillemots, higher heavy-metal levels were observed in those contam- inated quails that had also developed a cachectic status characterized by a general atrophy of their pectoral muscle and complete absence of subcutaneous and/or abdominal fat depots. Although likely the result of a general protein catabolism during starvation, it is suggested that these higher metal levels could as well enhance a general muscle wasting process (cachectic status). [less ▲]

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