References of "Lejeune, Pierre"
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See detailFrom nets to bottom traps: is exploitation of Norway lobsters a suitable option for Corsican common spiny lobster fishermen?
Patrissi, Michela; Astrou, Adèle; Pelaprat, Corinne et al

Poster (2014, May 20)

In Corsica (NW Mediterranean), most of the fishing activity is composed of small-scale artisanal fisheries, and takes place on the western coast. The common spiny lobster (Palinurus elephas) is the main ... [more ▼]

In Corsica (NW Mediterranean), most of the fishing activity is composed of small-scale artisanal fisheries, and takes place on the western coast. The common spiny lobster (Palinurus elephas) is the main target of Corsican netters. However, its populations have been declining since the 1950's, questioning the sustainability of this activity. We therefore tried to assess whether the fishing effort, currently mostly focused on common spiny lobsters, could be moved towards other commercially-interesting deep crustaceans, such as the Norway lobster (Nephrops norvegicus), through diversification of artisanal fishing practices. With the help of local fishermen, we set up Scottish traps for Norway lobsters at depths of 300 to 400 meters, on sandy and muddy bottoms of both eastern and western coasts. Despite several tests using different baits and soak times at various depths or seasons, catches on the western coast were low. On the other hand, on the eastern coast, experimentation showed interesting yields, and large mean size (i.e. high commercial value) for both sexes. While more studies are needed to confirm these results and improve knowledge of Norway lobster stocks, trap fishing of this species on eastern coast of Corsica could be a suitable alternative for diversification of artisanal fisheries. [less ▲]

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See detailSEDIMENTS OXIDATION BY SEAGRASSES: INFLUENCE ON THE S CYCLE IN POSIDONIA OCEANICA (L.) DELILE INTERMATTES DYNAMIC
Abadie, Arnaud ULg; Lejeune, Pierre; Pergent, Gérard et al

Poster (2014, May)

The Mediterranean seagrass Posidonia oceanica forms meadows and develops a complex of rhizomes, roots and sediment which is called “matte”. P. oceanica meadows show discontinuity patterns in the form of ... [more ▼]

The Mediterranean seagrass Posidonia oceanica forms meadows and develops a complex of rhizomes, roots and sediment which is called “matte”. P. oceanica meadows show discontinuity patterns in the form of sand or dead matte (matte without living shoots) patches, called “intermattes”, which can have natural or anthropogenic origins. Mechanical processes (e. g. currents, anchoring) can initiate intermattes formation but their dynamic after creation seems to be linked with the sediment chemistry, especially with S cycle. P. oceanica plays an important role in controlling coastal belowground biogeochemistry, in particular by oxidizing sediments through the release of O2 by roots. This process allows creating more suitable condition for plant growth and colonization. The lack of H2S oxidation in SO4 2- can lead to limitation of the plant development or its regression. In order to investigate the effect of oxidation condition in sediments on intermattes dynamic and the neighboring meadow, we initiate, in December 2013, a study on six intermattes (three natural, three anthropogenic) at different depths in Calvi Bay, in Corsica (France). We hypothesize that redox potential and H2S concentration in sediments play an important role in the regression of P. oceanica meadows, particularly after a mechanical anthropic impact like anchoring. It also may be possible that two different kinds of processes are involved for each type of intermatte. Regular samplings throughout two years are planed with the aim of evaluating the seasonal variations of physicochemical parameters. [less ▲]

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See detailNew insights for an old topic: seagrasses as bioindicators of coastal trace element pollution
Richir, Jonathan ULg; Lejeune, Pierre; Gobert, Sylvie ULg

in ARGYRO ZENETOS, ZENETOS (Ed.) Mediterranean Marine Science (2014, March)

The marine magnoliophyte Posidonia oceanica (L.) Delile has been widely used since the mid-70th to biomonitor the coastal pollution of the Mediterranean in Cr, Ni, Cu, Zn, Cd, Pb and/or Fe. In contrast ... [more ▼]

The marine magnoliophyte Posidonia oceanica (L.) Delile has been widely used since the mid-70th to biomonitor the coastal pollution of the Mediterranean in Cr, Ni, Cu, Zn, Cd, Pb and/or Fe. In contrast, other trace elements (TEs) like As, V, Ag, Be, Al, Mn, Co, Se, Mo, Sn, Sb and Bi, many of them categorized as TEs of environmental emerging concern, have been subject to nearly no ecotoxicological survey with that species. It has been shown that the French Mediterranean littoral was submitted to local, diffuse and/or chronic contaminations both by TEs broadly or little biomonitored with P. oceanica; high TE levels could further be linked to specific anthropic activities such as agriculture (Mo), mining (Cr, Sb, Zn), industries (As), storage and refinement of oil products (V, Pb) or presence of major ports and urban centres (Sn, Bi, Ag). It seems therefore necessary to expand the short list of the seven metals commonly monitored to other TEs, what is today easily achievable as current analytical methods allow the simultaneous determination of all a series of TEs within the same sample. Furthermore, only a multielement analysis in appropriate bioindicator species allow to correctly intercompare the pollution status of numerous sampling sites. To do this, we have calculated proper environmental indices, the trace element pollution index TEPI and the trace element spatial variation index TESVI. The TEPI is an index of the global contamination of a site, giving the same weight to each TE after mean normalization of their environmental concentrations. The TESVI estimates the global spatial variability of environmental concentrations of each TE levels, taking into account both punctual contaminations in impacted sites and the overall coastal spatial heterogeneity between all monitored sites.These two indices were successfully applied both at large (French Mediterranean littoral) and small (a Bay) spatial scales. Furthermore, they can be used in the framework of an intercomparative study compiling data from any previous monitoring surveys. We also highlighted that the ecophysiology and surrounding levels of TEs influenced in an equivalent manner the bioaccumulation process of TEs in P. oceanica. Consequently, this natural cyclic evolution of TE concentrations should be systematically quantified in regional reference sites. Finally, the rapid and proportionnal accumulation of TEs in P. oceanica traps huge amounts of contaminants and can stock them for longer periods of time in their bellow grounds tissues. P. oceanica meadows therefore play an efficient role of natural filter of TE coastal pollutions. [less ▲]

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See detailContrasting patterns of phytoplankton communities in two coastal ecosystems in relation to environmental factors (Corsica, NW Mediterranean Sea)
Garrido, Marie; Koeck, Barbara; Goffart, Anne ULg et al

in Diversity (2014), 6

Corsica Island is a sub-basin of the Northwestern Mediterranean Sea, with hydrological features typical of both oligotrophic systems and eutrophic coastal zones. Phytoplankton assemblages in two coastal ... [more ▼]

Corsica Island is a sub-basin of the Northwestern Mediterranean Sea, with hydrological features typical of both oligotrophic systems and eutrophic coastal zones. Phytoplankton assemblages in two coastal ecosystems of Corsica (the deep Bay of Calvi and the shallow littoral of Bastia) show contrasting patterns over a one-year cycle. In order to determine what drives these variations, seasonal changes in littoral phytoplankton are considered together with environmental parameters. Our methodology combined a survey of the physico-chemical structure of the subsurface water with a characterization of the phytoplankton community structure. Sampling provided a detailed record of the seasonal changes and successions that occur in these two areas. Results showed that the two sampled stations presented different phytoplankton abundance and distribution patterns, notably during the winter–spring bloom period. Successions in pico-, nano-, and microphytoplankton communities appeared mainly driven by differences in the ability to acquire nutrients, and in community-specific growth rates. Phytoplankton structure and dynamics are discussed in relation to available data on the Northwestern Mediterranean Sea. These results confirm that integrated monitoring of coastal areas is a requisite for gaining a proper understanding of marine ecosystems. [less ▲]

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See detailSynthèse des réseaux de surveillance soutenus par l’Agence de l’Eau Rhône Méditerranée Corse - eaux côtières de Méditerranée - juin 2013
Boissery, Pierre; Tomasino, Corinne; Giraud, Anaïs et al

Report (2013)

L’Agence de l’Eau Rhône Méditerranée Corse présente son premier atlas de la qualité des eaux marines issu des réseaux de surveillance des eaux côtières. Les résultats des mesures chimiques et biologiques ... [more ▼]

L’Agence de l’Eau Rhône Méditerranée Corse présente son premier atlas de la qualité des eaux marines issu des réseaux de surveillance des eaux côtières. Les résultats des mesures chimiques et biologiques, ainsi que l'analyse des pressions, montrent que les zones littorales et marines dégradées concernent 21% du linéaire méditerranéen et 19% de la mer, de la côte à 1 mille au large. Cette première édition regroupe les informations acquises sur la biologie (état de la faune, de la flore et de la biocénose), la chimie (contamination chimique, écotoxicologie et contamination de la chaîne trophique) et les pressions (activités de plaisance, usages en mer, rejets polluants et apports des cours d’eau côtiers) qui affectent le littoral. L'atlas couvre principalement la zone côtière mais il va s'étendre rapidement sur les eaux marines du large. [less ▲]

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See detailImpact des mouillages forains sur la qualité de l’eau et du phytoplancton : résultats d’une étude préliminaire menée en Baie de Calvi (Corse)
Goffart, Anne ULg; Lejeune, Pierre; Hecq, Jean-Henri ULg

Conference (2012, May 16)

Le plus souvent, l’étude de l’impact des mouillages forains sur l’environnement aquatique concerne l’analyse des dégradations subies par la faune et la flore benthiques. Cependant, dans nos régions, la ... [more ▼]

Le plus souvent, l’étude de l’impact des mouillages forains sur l’environnement aquatique concerne l’analyse des dégradations subies par la faune et la flore benthiques. Cependant, dans nos régions, la grande majorité des bateaux de plaisance construits avant 2008 et de longueur inférieure à 24 mètres ne sont pas équipés d'installations de stockage des eaux résiduaires (eaux ménagères, douches, eaux noires des toilettes) et encore moins de traitement à bord des effluents. Une partie des eaux usées de la plaisance est donc rejetée en mer sans que leur charge polluante et leur impact sur les eaux de surface ne soient connus. De mai à septembre 2011, une étude pilote a été menée dans une zone de mouillage forain de taille moyenne de la Baie de Calvi (site de l’Alga) dans le double but d’analyser la qualité du phytoplancton (biomasse et composition) et la charge en Escherichia coli des eaux de surface. Les données obtenues à l’Alga sont comparées à celles du point de référence DCE pour l’étude du phytoplancton, situé à proximité de STARESO. Les résultats obtenus à l’Alga mettent en évidence les éléments suivants : 1. Biomasse phytoplanctonique totale : la biomasse phytoplanctonique totale de l’Alga est proche de celle mesurée à la station de référence; 2. Composition phytoplanctonique : alors que la composition du phytoplancton du site de référence est constante au cours de la saison estivale, le phytoplancton de l’Alga se caractérise par une augmentation progressive de la concentration en Cyanobactéries, un groupe dont la croissance est favorisée par la présence d’ammonium; 3. Charge en E. coli : des concentrations de 100 à 300 E. coli par 100 ml d’eau sont mesurées de juillet à septembre dans tous les échantillons de surface de la zone de mouillage alors qu’elles sont toujours absentes de la station de référence. Les apports diffus liés aux rejets des eaux usées de la plaisance paraissent donc suffisants pour affecter la composition du phytoplancton et la charge bactérienne des eaux de surface d’une zone de mouillage forain de taille moyenne. Les implications en termes d’impact sur la qualité de l’eau et de l’écosystème seront discutées. Depuis mars 2012, un suivi complet de l’influence de la zone de mouillage forain de l’Alga sur l’écosystème côtier est réalisé dans le cadre du projet STARECAPMED. [less ▲]

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See detailThe seascape as an indicator of environmental interest and quality of the Mediterranean benthos: the in situ development of a description index: the LIMA
Gobert, Sylvie ULg; Chéry, Aurélia; Volpon, Alexandre et al

Conference (2011, March)

The LIMA index conveys the environmental interest and quality of the landscape formed by the Mediterranean benthos, ranging from 0 to -40 m, in numerical format. The LIMA index allows a comparison ... [more ▼]

The LIMA index conveys the environmental interest and quality of the landscape formed by the Mediterranean benthos, ranging from 0 to -40 m, in numerical format. The LIMA index allows a comparison spatially and temporarily between sites. It is a comprehensive index which is easy to implement and is composed of two factors: a topographical description (classification of 15 typologies) and a biological description (the presence or absence of some thirty species or groups of structuring, remarkable and invasive species). The LIMA index has been validated in the Bay of Calvi (Corsica-France) where it varies between 0.31 and 0.79 on a scale of 0.00 to 1.00. [less ▲]

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

Conference (2010, May)

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

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

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See detailProblematic of the Pelagia noctiluca outbreaks in the Bay of Calvi (Corsica)
Hecq, Jean-Henri ULg; Goffart, Anne ULg; Collignon, Amandine ULg et al

in Proceedings of the 39th CIESM Congress (2010)

The interannual variations of the Schyphozoan jellyfish Pelagia noctiluca is estimated by weekly measurements in the Bay of Calvi (Corsica) from 2003. The mean annual abundance reaches a dramatic maximum ... [more ▼]

The interannual variations of the Schyphozoan jellyfish Pelagia noctiluca is estimated by weekly measurements in the Bay of Calvi (Corsica) from 2003. The mean annual abundance reaches a dramatic maximum in 2006. The medusae appear by migration of active swarms on the shelf and at the external limit of the Bay. Degraded individuals drift as passive swarms, throughout inner side of the Bay and embayments. [less ▲]

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See detailLa variabilité de la méduse Pelagia noctiluca (Forskål, 1775) en Baie de Calvi (Corse) en relation avec l’environnement
Hecq, Jean-Henri ULg; Goffart, Anne ULg; Collignon, Amandine ULg et al

Report (2009)

Depuis une dizaine d’années, les apparitions massives de la méduse scyphozoaire Pelagia noctiluca (Forskål) sont de plus en plus fréquentes en Méditerranée Occidentale. Ces pullulations perturbent les ... [more ▼]

Depuis une dizaine d’années, les apparitions massives de la méduse scyphozoaire Pelagia noctiluca (Forskål) sont de plus en plus fréquentes en Méditerranée Occidentale. Ces pullulations perturbent les activités récréatives, en causant des brûlures douloureuses aux baigneurs. Elles interfèrent avec la pêche, colmatent les filets et entrent en compétition avec les poissons pour la nourriture. Elles peuvent également tuer les poissons et leurs larves dans les enclos d’aquaculture, ou boucher les canalisations des centrales électriques et de dessalage. Ces pullulations constituent donc une nuisance pour les eaux de baignade et les installations aquacoles et hydrauliques côtières. Cependant, l’éradication ou simplement le contrôle des populations de méduses reste impossible à l’heure actuelle, car leur distribution est à large échelle et déborde largement du plateau continental. L eurs apparitions dans les eaux côtières sont généralement fortuites, discontinues dans le temps et dans l’espace et généralement sous forme d’essaims. Pour ces mêmes raisons, l’écologie des méduses, les causes des pullulations et leur impact sur la chaîne alimentaire sont mal connues et font l’objet d’interprétations contradictoires par les médias. Leur taxonomie, la multiplicité de leurs formes et de leurs cycles de développement restent imprécis. Grâce au soutien de l’Agence Française de l’Eau Rhône Méditerranée et Corse, de la communauté Française de Belgique (Programme RACE), du Fond Belge de la Recherche Scientifique (FRS-FNRS), de STARESO et de l’Université de Liège, une approche scientifique de la variabilité de la méduse scyphozoaire Pelagia noctiluca (Forskål) a été entreprise en Baie de Calvi (Corse) en relation avec et les changements environnement. Les objectifs principaux de cette action menée à la station STARESO sont de contribuer à comprendre et à prévoir les fluctuations d’abondance de cette espèce - clé en réponse aux variations de l’environnement, sur base d’observations de terrain et de la synthèse d’informations existantes. Elle a pour but de développer un schéma conceptuel et une base de données susceptibles d’intervenir comme outil prédictif des populations de méduses en Méditerranée Occidentale. Une synthèse de la littérature scientifique a porté sur la morphologie, la dangerosité, le cycle de reproduction et le développement de, sa nutrition et son métabolisme, sa distribution spatiale et temporelle et sur les méthodes d’investigation et de comptages. Des mesures hebdomadaires effectuées depuis 2003 à partir du quai de STARESO ont permis de montrer une augmentation graduelle de l‘abondance de la méduse Pelagia noctiluca de 2004 à 2005, suivie d’une augmentation dramatique en 2006, puis d’une diminution significative les étés 2007 et 2008. Ces mesures ont permis également d’aborder la formation des essaims et tenté d’expliquer les causes de leur accumulation le long des plages. [less ▲]

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See detailLa problématique des méduses sur le plateau continental Ouest Corse, série de données et modélisation
Hecq, Jean-Henri ULg; Goffart, Anne ULg; Collignon, Amandine ULg et al

Conference (2009)

Depuis une dizaine d’années, les eaux côtières corses sont envahies les méduses et en particulier par les Pelagia noctiluca qui présentent une nuisance pour les eaux de baignade, les installations ... [more ▼]

Depuis une dizaine d’années, les eaux côtières corses sont envahies les méduses et en particulier par les Pelagia noctiluca qui présentent une nuisance pour les eaux de baignade, les installations aquacoles et hydrauliques côtières, interfèrent avec la pêche, colmatent les filets et entrent en compétition avec les poissons pour la nourriture. Leurs apparitions dans les eaux côtières sont généralement fortuites, discontinues dans les temps et dans l’espace et souvent sous forme d’essaims. Dans le cadre du programme MEDUSES, subsidié par l’Agence de l’Eau RMC, des observations visuelles directes et des comptages de Pelagia effectués depuis 2003 à partir du quai du port de STARESO montrent une augmentation graduelle de leur abondance de 2004 à 2005 suivie par une augmentation dramatique en 2006 puis une diminution significative les étés 2007 et 2008. La prolifération de Pelagia en 2006 succède à des biomasses particulièrement élevées de mésozooplancton en 2005. On peut émettre l’hypothèse que l’abondance exceptionnelle des proies planctoniques est une des causes de la prolifération. Les Pelagia vivent en essaims dont deux types sont observés en Baie de Calvi: des essaims passifs et des essaims actifs. Les essaims passifs observés dans le port de STARESO contiennent des individus généralement dégradés (perte des tentacules, du manubrium,..), voire moribonds mais qui restent urticants. Parfois réduits à la seule ombrelle, ils se déplacent peu et s’accumulent en grand nombre (parfois plus de 200 par m2), bord à bord, en essaims passifs limités aux trois premiers mètres de la surface. Ces essaims subissent une prédation active par de nombreux poissons sparidés (bogues, sars,...). Ils disparaissent en quelques heures du fait de cette prédation ou par sédimentation massive des animaux morts. Par contre, dans les eaux plus au large, nos mesures in situ de la distribution spatiale de Pelagia noctiluca montrent que durant les pics de 2006, de nombreux organismes sont présents à distance de la côte où ils forment des essaims actifs de 200 m de long et 50 m de large situés entre 10 à 60 m. Dans ces essaims actifs, on observe de 5 à 10 individus par m3. Ceux-ci sont équidistants et nagent activement avec les tentacules étendus, capturant la nourriture. Dans certains cas, des individus moribonds partiellement détruits ou à la fin de leur cycle biologique échappent des essaims actifs et dérivent passivement à la surface, sous l’action du vent et des mouvements de l’eau, vers les zones côtières. Entre ces deux types extrêmes d’essaims, divers cas intermédiaires existent. [less ▲]

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See detailAssessment of the ecological status of Mediterranean French coastal waters as required by the Water Framework Directive using the Posidonia oceanica Rapid Easy Index: PREI
Gobert, Sylvie ULg; Sartoretto, Stéphane; Rico-Raimondino, Valérie et al

in Marine Pollution Bulletin (2009), 58

This paper describes the PREI (Posidonia oceanica Rapid Easy Index), a method used to assess the ecological status of seawater along Mediterranean French coasts. The PREI was drawn up according to the ... [more ▼]

This paper describes the PREI (Posidonia oceanica Rapid Easy Index), a method used to assess the ecological status of seawater along Mediterranean French coasts. The PREI was drawn up according to the requirements of the Water Framework Directive (WFD 2000/60/EC) and was tested on 24 and 18 stations in PACA (Provence-Alpes-Côtes d’Azur) and Corsica respectively. The PREI is based on five metrics: shoot density, shoot leaf surface area, E/L ratio (Epiphytic biomass/leaf biomass), depth of lower limit, and type of this lower limit. The 42 studied stations were classified in the first four levels of status: high, good, moderate and poor. The PREI values ranged between 0.280 and 0.847; this classification is in accordance with our field knowledge and with our knowledge of the literature. The PREI was validated regarding human pressure levels (r²= 0.74). (http://eurex.europa.eu/LexUriServ/LexUriServ.do?uri=OJ:L:2000:327:0001:0072:EN:PDF) [less ▲]

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See detailSpatial and interannual variability of the Schyphozoan medusae, Pelagia noctiluca (Forksål), in the Bay of Calvi (Corsica)
Collignon, Amandine ULg; Goffart, Anne ULg; Lejeune, Pierre et al

Poster (2008, October)

The temporal distribution of the Schyphozoan medusae Pelagia noctiluca (Forksål) has been examined weekly in the oligotrophic coastal waters of the Bay of Calvi (Corsica) from 2003 to 2008. The ... [more ▼]

The temporal distribution of the Schyphozoan medusae Pelagia noctiluca (Forksål) has been examined weekly in the oligotrophic coastal waters of the Bay of Calvi (Corsica) from 2003 to 2008. The observations show a gradual increase of jellyfish number in 2004 to 2005, followed by a dramatic increase in the 2006 and a significant reduction in summers 2007 and 2008. The numeration of ephyra larvae in plankton and ovarian histology show a higher reproduction in June 2006. An analysis of the spatial distribution of the Pelagia noctiluca in the area of the Bay of Calvi emphasises that during the 2006 bloom, most of the organisms are present at a distance of the coastline where they are forming actives swarms of 200 m of length with 5 to 10 individual per m3. In the swarms, the individuals are healthful and swim actively in the upper layer (10 t 60 m) with tentacles extended, probably catching the food. The swarms are generally located around wind-protected area where the surface turbulence is reduced and where zooplankton is accumulating. Sometimes, the swarms migrate vertically probably in relation with changes of wind conditions. In some cases, moribund individuals partially destroyed or at the end of their biological cycle escape from active swarms and drift passively, at the surface, under the action of water movements, into coastal waters and beaches where they accumulate and reach 200 individual per m3. In these passive swarms the individuals continue to swim slowly but are actively fed by some Sparid fish. [less ▲]

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See detailDirective Cadre Eau: Mise en oeuvre du contrôle de surveillance - résultats de la campagne 2006 - district Corse
Boissery, Pierre; Andral, Bruno; Belin, Catherine et al

Report (2007)

Les programmes de surveillance liés à la mise en oeuvre de la DCE sont coordonnés par le Ministère de l’Ecologie et de l’Aménagement durable (MEDAD) et dans chaque bassin hydrographique ce sont les ... [more ▼]

Les programmes de surveillance liés à la mise en oeuvre de la DCE sont coordonnés par le Ministère de l’Ecologie et de l’Aménagement durable (MEDAD) et dans chaque bassin hydrographique ce sont les Agences de l’eau qui, avec l’Etat, prennent en charge l’application, la mise en oeuvre de ces réseaux. Sur la façade méditerranéenne, Ifremer a assuré pour le compte du Schéma Directeur des Données sur l’Eau la maîtrise d’ouvrage de la première campagne du contrôle de surveillance, en coordonnant l’ensemble de l’acquisition des données et de leur synthèse en collaboration avec de nombreux partenaires : Universités, bureaux d’études, structures locales de gestion et services de l’Etat. La mobilisation des différents acteurs autour d’un objectif commun a permis de faire face à la pluridisciplinarité et à la complexité des aspects logistiques de ce programme. Les résultats de cette première campagne du contrôle de surveillance (2006) permettent d’ores et déjà d’avoir une bonne vision d’ensemble de la qualité des eaux littorales à l’échelle du district. Ils confortent les évaluations faites « à dire d’expert » lors de l’état des lieux du district avec des informations nouvelles concernant plus particulièrement la biologie, notamment le benthos de substrat meuble. En eaux côtières, les eaux sont de bonne qualité. En eau de transition, essentiellement lagunaires, il existe une plus grande hétérogénéité des résultats avec des paramètres déclassant relevant plutôt de la biologie, mais sur un nombre important d’indicateurs. [less ▲]

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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 detailCytokinin levels in leaves, leaf exudate and shoot apical meristem of Arabidopsis thaliana during floral transition
Corbesier, Laurent; Prinsen, Els; Jacqmard, Annie ULg et al

in Journal of Experimental Botany (2003), 54(392), 2511-2517

Understanding the complete picture of floral transition is still impaired by the fact that physiological studies mainly concern plant species whose genetics is poorly known, and vice versa. Arabidopsis ... [more ▼]

Understanding the complete picture of floral transition is still impaired by the fact that physiological studies mainly concern plant species whose genetics is poorly known, and vice versa. Arabidopsis thaliana has been successfully used to unravel signalling pathways by genetic and molecular approaches, but analyses are still required to determine the physiological signals involved in the control of floral transition. In this work, the putative role of cytokinins was investigated using vegetative plants of Arabidopsis (Columbia) induced to flower synchronously by a single 22 h long day. Cytokinins were analysed in leaf extracts, leaf phloem exudate and in the shoot apical meristem at different times during floral transition. It was found that, in both the leaf tissues and leaf exudate, isopentenyladenine forms of cytokinins increased from 16 h after the start of the long day. At 30 h, the shoot apical meristem of induced plants contained more isopentenyladenine and zeatin than vegetative controls. These cytokinin increases correlate well with the early events of floral transition. [less ▲]

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See detailN content of phloem and xylem exudates during the transition to flowering in Sinapis alba and Arabidopsis thaliana
Corbesier, Laurent; Havelange, Andrée ULg; Lejeune, Pierre et al

in Plant, Cell & Environment (2001), 24

The involvement of nitrogenous substances in the transition to flowering was investigated in Sinapis alba and Arabidopsis thaliana (Columbia). Both species grown in short days (SD) are induced to flower ... [more ▼]

The involvement of nitrogenous substances in the transition to flowering was investigated in Sinapis alba and Arabidopsis thaliana (Columbia). Both species grown in short days (SD) are induced to flower by one long day (LD). In S. alba, the phloem sap (leaf and apical exudates) and the xylem sap (root exudate) were analysed in LD versus SD. In A. thaliana, only the leaf exudate could be analysed but an alternative system for inducing flowering without day-length extension was used: the displaced SD (DSD). Significant results are: (i) in both species, the leaf exudate was enriched in Gln during the inductive LD, at a time compatible with export of the floral stimulus; (ii) in S. alba, the root export of amino acids decreased in LD, whereas the nitrate remained unchanged - thus the extra-Gln found in the leaf exudate should originate from the leaves; (iii) extra-Gln was also found very early in the apical exudate of S. alba in LD, together with more Glu; (iv) in A. thaliana induced by one DSD, the leaf export of Asn increased sharply, instead of Gln in LD. This agrees with Asn prevalence in C-limited plants. The putative role of amino acids in the transition to flowering is discussed. [less ▲]

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See detailChanges in amino acid content during floral induction in the leaf exudate collected form the long day plant Arabidopsis thaliana
Corbesier, Laurent; Lejeune, Pierre; Bernier, Georges et al

Poster (2000)

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See detailPhysiological analysis of the floral transition
Bernier, Georges ULg; Corbesier, Laurent; Périlleux, Claire ULg et al

in Cockshull, K. E.; Gray, D.; Seymour, G. B. (Eds.) et al Genetic and Environmental Manipulation of Horticultural Crops (1998)

This chapter summarizes the changes in contents of the phloem sap that were found at the time of floral induction in different photoperiodic species: Arabidopsis thaliana, Sinapis alba, Lolium temulentum ... [more ▼]

This chapter summarizes the changes in contents of the phloem sap that were found at the time of floral induction in different photoperiodic species: Arabidopsis thaliana, Sinapis alba, Lolium temulentum and Xanthium strumarium. Changes affecting contents in carbohydrates, cytokinins, amino acids, polyamines and inorganis ions are discussed in the context of 'florigen quest'. [less ▲]

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