References of "Poulicek, Mathieu"
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See detailFlore et faune de l'estran. Régions de Wimereux (Pas-de-Calais) et de Roscoff (Finistère)
Bussers, Jean-Claude ULg; Jeuniaux, Charles; Thomé, Jean-Pierre ULg et al

Learning material (2014)

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See detailNatural spatial variability of algal endosymbiont density in the coral Acropora globiceps: a small-scale approach along environmental gradients around Moorea (French Polynesia)
Ladrière, Ophélie ULg; Penin, Lucie; Van Lierde, Elodie et al

in Journal of the Marine Biological Association of the United Kingdom (2013)

This study provides a baseline describing natural small scale variability of Symbiodinium density in the sentinel coral Acropora globiceps during the summer, under non-bleaching conditions. Spatial scales ... [more ▼]

This study provides a baseline describing natural small scale variability of Symbiodinium density in the sentinel coral Acropora globiceps during the summer, under non-bleaching conditions. Spatial scales investigated range from the colony scale (1–10 cm, i.e. among branches of the same colony) to the reef scale (1–10 km, i.e. among stations distributed over several locations and depths), at Moorea Island, French Polynesia. The coral–Symbiodinium symbiosis is a key process in scleractinian coral physiology, and Symbiodinium density provides an easy-to-measure and inexpensive biomarker of this symbiosis health. Spatial variability of three major environmental factors: light intensity, sedimentation and water motion was also assessed to evaluate their potential link with Symbiodinium density. Density of Symbiodinium did not significantly differ within colonies or among colonies within a station. However, a marked depth gradient was observed, showing increasing density with increasing depth and decreasing light intensity. These observations provide an interesting reference for forthcoming comparisons with disturbed conditions, such as bleaching events. [less ▲]

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See detailINVENTAIRE MALACOLOGIQUE DU DOMAINE FORESTIER UNIVERSITAIRE DU SART TILMAN
Léonard, Lilian; Delcourt, Johann ULg; Vilvens, Claude et al

Report (2013)

The Sart Tilman is a vast wooded area of 754 ha located on the south of the city of Liege that hosts the campus of the University of Liege. It is the only large remaining peri-urban forest of this city ... [more ▼]

The Sart Tilman is a vast wooded area of 754 ha located on the south of the city of Liege that hosts the campus of the University of Liege. It is the only large remaining peri-urban forest of this city. The installation of the University in this place was planned in order to discard the threads of real estate business. The absence of major silvicultural treatments for over 50 years has allowed the forest gradually recovering some dynamics of a natural ecosystem although its composition remains largely influenced by past management. Its interest as multi-use area and particularly as a biodiversity reserve is recognized. Nevertheless, internal pressures similar to urbanization spread threaten the integrity of the area. The Scientific Council of the Sites of the Sart Tilman, which is in charge of maintaining the integrity, and promoting the scientific, educational, and aesthetic development of the area, would like to dispose of more biodiversity distribution data to carry on its missions. The present study is an analysis of the malacological diversity of Sart Tilman taking into account the diversity of forest stands. The work began with the design and evaluation of an effective protocol to allow a malacological inventory in the most comprehensive manner as possible. An inventory protocol combining three methods has been applied to the field with a stratified sample strategy taking into account forest type. The inventory reports a list of 43 species and estimates that 5 to 7 additional species are potentially present. The diversity was modelled as a function of environmental descriptors. Models show meaningful effects of drainage, soil pH, and forest type on the richness and species diversity. However, the predictive ability of these models is insufficient to directly predict malacological diversity and to establish scale mapping of the Sart Tilman. Otherwise, malacological diversity is correlated with an index of potential biodiversity resulting from the combination of 10 easily observable indicators like the number of native tree species or the stratification of the stands. [less ▲]

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See detailUse of semi-quantitative kit methods to study the heterotrophic bacterial community of Posidonia oceanica meadows: Limits and possible applications
Richir, Jonathan ULg; Velimirov, Branko; Poulicek, Mathieu ULg et al

in Estuarine Coastal & Shelf Science (2012), 109

Rapid, easy and low cost semi-quantitative methods were tested to study the heterotrophic bacterial community of Posidonia oceanica meadows and were compared to techniques commonly used in microbial ... [more ▼]

Rapid, easy and low cost semi-quantitative methods were tested to study the heterotrophic bacterial community of Posidonia oceanica meadows and were compared to techniques commonly used in microbial ecology. Free and pore-water bacterial densities were estimated by luminescence, and principal enzymatic activities, metabolic capabilities and benthic mineralisation processes were studied with microtitration methods: ApiZym galleries, Biolog microplates and BART tests. Bacterial densities varied little throughout the year and were around 5.0 10^5 and 6.0 10^6 cells ml -1 of free and pore-water, respectively. The combined use of the ApiZym gallery and the Biolog microtitration plate permitted highlighting bacterial enzymatic activities susceptible to degrade principal organic polymers present in the Posidonia meadow, and to correlate these enzymatic activities to the subsequent potential utilization of resulting monomeric products. Levels of enzymatic activities (1.80-8.36 nmoles substrates h -1 ml- 1) and energetic bacterial metabolism (1.80-6.42 nmoles substrates h -1 ml- 1) presented seasonality relying on the temperature regime and on the primary production (Posidonia and phytoplankton). Main mineralization processes of buried organic matter through sulfate and iron reduction activities were successfully detected. Despite the complexity of the studied ecosystem, results obtained by this semi-quantitative approach, compared to studies applying commonly used methods in microbial ecology, highlighted the same bacterial dominant key processes. Their low cost, rapid and easy use, and the low level of expertise and sophistication they require means that these techniques are of use to many employed in environmental surveys. [less ▲]

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See detailAlternative photosynthetic electron pathways in different clades of Symbiodinium: the Mehler reaction
Roberty, Stéphane ULg; Poulicek, Mathieu ULg; Franck, Fabrice ULg

Poster (2010, December)

The high productivity of coral reef ecosystems is largely attributed to the mutualistic symbiosis between reef-building corals and their intracellular dinoflagellate in the genus Symbiodinium commonly ... [more ▼]

The high productivity of coral reef ecosystems is largely attributed to the mutualistic symbiosis between reef-building corals and their intracellular dinoflagellate in the genus Symbiodinium commonly referred to as zooxanthellae. These photosynthetic algae translocate a majority of their photosynthetically fixed carbon to the host and contribute greatly to their metabolic needs (Muscatine, 1990) and the calcification process (Gattuso, 1999). In the natural environment the holobiont have to cope with significant daily variations in light intensities that sometimes exceed Symbiodinium photosynthetic capacity. Fortunately, photosynthetic organisms possess regulatory features that help to ensure that high light intensities can be endured without the accumulation of photodamage. Thus, the regulation of photosynthesis can be viewed as a dynamic balance between photosynthetic efficiency (photochemical quenching) and photoprotection processes (i.e. non-photochemical quenching). Among them, the role of O2 as an alternative electron acceptor within the chloroplast could play a critical role (Ort & Baker, 2002). Under particular environmental conditions when sinks for photosynthetic electrons are scarce, the direct reduction of oxygen by the PSI could sustain significant levels of photosynthetic electron flux by initiating the ΔpH formation and of NPQ, regulating the ratio of ATP/NADPH to match the requirements of carbon reduction. However, this process leads to the formation of reactive oxygen species that are rapidly detoxified by superoxide dismutase and ascorbate peroxidase. An additional electron flux associated with this oxygen pathway is directed to the reduction of monodehydroascorbate (MDA), which is generated as a result of peroxide reduction by ascorbate (Asada, 2000). The present study aimed to highlight the existence of alternative photosynthetic electron pathways and more especially the Mehler ascorbate peroxidase pathway in different clades of Symbiodinium, cultivated at low and high light intensities. -Muscatine L (1990) The role of symbiotic algae in carbon and energy flux in reef corals. In: Dubinsky Z(ed) Ecosystems of the world: coral reefs. Elsevier, Amsterdam, pp 1-9. -Gattuso JP, Allemand D and M Frankignoulle (1999) Photosynthesis and calcification at cellular, organismal and community levels in coral reefs: A review on interactions and control by carbonate chemistry. American Zoologist 39(1): 160-183. -Ort, D. R. and N. R. Baker (2002). A photoprotective role for O2 as an alternative electron sink in photosynthesis? Current Opinion in Plant Biology 5(3): 193-198. -Asada, K. (2000) The water-water cycle as alternative photon and electron sinks. Philosophical Transactions of the Royal Society B-Biological Sciences 355(1402): 1419–1431. [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 detailSYMBIODINIUM SP. CAN STAY ALIVE THROUGH THE GUT AND IN THE FAECES OF CNIDARIA. PREDATORS. THE CASE OF CORALLIOPHILLA MEYENDORFFI AND ANEMONIA VIRIDIS.
Poulicek, Mathieu ULg; Roberty, Stéphane ULg; Plaza, Sylvain et al

Poster (2010)

The gastropod Coralliophilla meyendorffi is a common predator of the zooxanthellate anemone Anemonia viridis. Zooxanthella from the anemones are an important constitutent of the mollusc faeces. Cell ... [more ▼]

The gastropod Coralliophilla meyendorffi is a common predator of the zooxanthellate anemone Anemonia viridis. Zooxanthella from the anemones are an important constitutent of the mollusc faeces. Cell integrity, occurence of flagellated forms, live/dead proportions and mitotic index of Symbiodinium collected from the faeces and cultivated in vitro were examined and compared to that of algae in hospite. The results show that most algae withstand digestive processes of the predator, staying alive and dividing actively in the faeces. Motile (lagellated) algae arise from dividing cells and escape the fecal pellets. Impact on coral bleaching recovery is discussed. [less ▲]

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See detailPhotoacclimation responses of a symbiotic sea anemone reveal an important host cellular plasticity
Roberty, Stéphane ULg; Fransolet, David ULg; Ladrière, Ophélie ULg et al

Poster (2010)

The high productivity of coral reef ecosystems is largely attributed to the mutualistic symbiosis between reef-building corals and their intracellular dinoflagellate in the genus Symbiodinium commonly ... [more ▼]

The high productivity of coral reef ecosystems is largely attributed to the mutualistic symbiosis between reef-building corals and their intracellular dinoflagellate in the genus Symbiodinium commonly referred to as zooxanthellae. These photosynthetic algae translocate a majority of their photosynthetically fixed carbon to the host and contribute to their metabolic needs and the calcification process. <i>Symbiodinium</i> must maintain a balance between the energy derived from the light reactions in the chloroplast and the amount of energy used during dark reactions and other metabolic processes. Nevertheless, in the natural environment the holobiont have to cope with daily and seasonal changes in light intensity, upsetting that balance and creating a stress that induces a physiological response (photoacclimation) to optimize growth rates. After a ten day exposition to high and very low light intensity, morphological and photophysiological analysis conducted on the symbiotic sea anemone, Anemonia manjano, reveal significant modifications of the host tissues ultrastructure and the Symbiodinium metabolic processes (photosynthesis, respiration). Those results highlight particularly important gastrodermal and ectodermal plasticity in which symbiotic cnidarians acclimate to the Symbiodinium physiological status (mainly photosynthesis) by varying the density of particular cellular types (e.g.: cnidocytes, gastrodermal cells) contained in their tissues. [less ▲]

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See detailUne coquille, qu'est-ce que c'est?
Poulicek, Mathieu ULg

in Coquilles coquines (2009)

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See detailUne coquille : archive du passé
Poulicek, Mathieu ULg

in Coquilles coquines (2009)

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See detailCoquille : symbole, art et parure
Poulicek, Mathieu ULg

in Coquilles coquines (2009)

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See detailCoquilles coquines, les attraits des Mollusques
Poulicek, Mathieu ULg

in Coquilles coquines (2009)

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See detailHETEROGENEITY OF ZOOXANTHELLAE DENSITY IN THE CORAL ACROPORA GLOBICEPS AROUND MOOREA (FRENCH POLYNESIA)
Ladrière, Ophélie ULg; van Lierde, Elodie; Penin, Lucie et al

Poster (2008)

Understanding the natural heterogeneity of coral zooxanthellae density appears as very important to understand variations in coral survival due to bleaching (the loss of these micro-algal symbionts ... [more ▼]

Understanding the natural heterogeneity of coral zooxanthellae density appears as very important to understand variations in coral survival due to bleaching (the loss of these micro-algal symbionts). Heterogeneity of coral bleaching at different observation scales (within a colony, among neighbouring colonies of the same species or on a wider scale) remains largely misunderstood. The present work explores intracolonial, spatial and temporal variations of zooxanthellae density in the coral Acropora globiceps Dana 1846, over a period of three months on the forereef of Moorea, French Polynesia. In our study, intracolonial zooxanthellae densities did not vary significantly. However, zooxanthellae densities differed slightly between inner and outer branches but this trend was not significant at 6, 12 and 18 meters depth. On a wider scale, zooxanthellae densities also vary spatially : a positive correlation was observed between depth and symbiont density (density increases when light intensity decreases, so according to depth). Moreover, the location of colonies exposed to different hydrodynamical conditions was not a parameter controling the concentration of zooxanthellae. Finally, the temporal variation of zooxanthellae densities did not show significant variations even if it decreased slightly over the study period. The results of this study highlight the importance of accounting for variations within and among colonies to determine zooxanthellae densities and to assess the evolution of zooxanthellae populations. [less ▲]

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See detailHeterogeneity of zooxanthellae density in the coral Acropora globiceps around Moorea (French Polynesia)
Ladrière, Ophélie ULg; van Lierde, Elodie; Penin, Lucie et al

Poster (2008)

Understanding the natural heterogeneity of coral zooxanthellae density appears as very important to understand variations in coral survival due to bleaching (the loss of these micro-algal symbionts ... [more ▼]

Understanding the natural heterogeneity of coral zooxanthellae density appears as very important to understand variations in coral survival due to bleaching (the loss of these micro-algal symbionts). Heterogeneity of coral bleaching at different observation scales (within a colony, among neighbouring colonies of the same species or on a wider scale) remains largely misunderstood. The present work explores intracolonial, spatial and temporal variations of zooxanthellae density in the coral Acropora globiceps Dana 1846, over a period of three months on the forereef of Moorea, French Polynesia. In our study, intracolonial zooxanthellae densities did not vary significantly. However, zooxanthellae densities differed slightly between inner and outer branches but this trend was not significant at 6, 12 and 18 meters depth. On a wider scale, zooxanthellae densities also vary spatially : a positive correlation was observed between depth and symbiont density (density increases when light intensity decreases, so according to depth). Moreover, the location of colonies exposed to different hydrodynamical conditions was not a parameter controling the concentration of zooxanthellae. Finally, the temporal variation of zooxanthellae densities did not show significant variations even if it decreased slightly over the study period. The results of this study highlight the importance of accounting for variations within and among colonies to determine zooxanthellae densities and to assess the evolution of zooxanthellae populations. [less ▲]

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See detailPotential implication of host/symbiont recognition mechanisms in coral bleaching
Vidal-Dupiol, Jérémie; Mitta, Guillaume; Roger, Emmanuel et al

Poster (2008)

Bleaching in corals can be attributed to loss of endosymbiotic zooxanthellae and/or loss of photosynthetic pigments within zooxanthellae. This major disturbance of the reef ecosystem is principally ... [more ▼]

Bleaching in corals can be attributed to loss of endosymbiotic zooxanthellae and/or loss of photosynthetic pigments within zooxanthellae. This major disturbance of the reef ecosystem is principally induced by increases in water temperature. Since the beginning of the 80ís and the onset of global climate change, this phenomenon has been occurring at increasing rates and scales, and with increasing severity. In this study, we focused on finding early regulated genes involved in bleaching. In aquaria, one set of Pocillopora damicornis nubbins was subjected to a gradual seawater temperature increase from 28°C to 32°C over 15 days, and a second control set remained at constant temperature (28°C). Bleaching was monitored by measuring zooxanthellae density. The mRNA differentially expressed between the stressed state (sampled just before the onset of bleaching) and the non stressed state (control) were isolated from the nubbins by Suppression Subtractive Hybridization. The corresponding cDNA were sequenced and confronted to sequence databases to obtain gene similarities. Finally, transcription rates of the most interesting genes were conducted by Q-PCR. Two particularly interesting candidate genes showed an important decrease in their transcription rates following thermal stress and before zooxanthellae loss. These two genes show similarities with genes involved in host/symbiont and host/parasite models. The implication of these molecular actors suggests a possible role of recognition mechanisms between the host and its symbiont, in the breakdown of the symbiosis during the bleaching phenomenon. Experiments such as RACE-PCR, in situ hybridization and immunohistochemistry are currently underway to confirm our hypotheses. [less ▲]

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See detailMorphological alterations of zooxanthellae in bleached cnidarian hosts
Ladrière, Ophélie ULg; Compère, Philippe ULg; Decloux, Nicole ULg et al

in Cahiers de Biologie Marine (2008), 49(3), 215-227

Studying the morphological changes of zooxanthellae in the host gastroderm is essential to understand the mechanisms of bleaching. Transmission electron microscopy was used to observe samples from four ... [more ▼]

Studying the morphological changes of zooxanthellae in the host gastroderm is essential to understand the mechanisms of bleaching. Transmission electron microscopy was used to observe samples from four coral species-three collected from a barrier reef in Madagascar (Acropora digitifera (Dana, 1846), Echinopora hirsutissima Milne-Edwards & Haime, 1849 and Porites (Synaraea) rus Forskal, 1775)) and one cut from an aquarium-grown coral (Pocillopora damicornis (Linnaeus, 1758)-and from the hermatypic (zooxanthellae-containing) sea anemone Aiptasia pulchella (Carlgren, 1943). Zooxanthellae from bleached animals showed different stages of degradation or disorganization. Some were free, detached from the host gastroderm, associated or not with host-cell remains. Others were vacuolated, with abundant reserve material globules and angular holes probably created by the loss of crystalline material during cutting. Experimentally heat-shocked P. damicornis harboured, moreover, a greater number of dividing algae. Bleached individuals were found to vary as regards their response to stress, and zooxanthellae expelled from heat-shocked anemones showed a greater mitotic index and a higher survival rate than algae extracted or naturally externalized from healthy individuals. We propose a combination of morphological criteria for use in diagnosing the health state of algae-cnidarian symbiosis, so vulnerable in the case of bleaching. [less ▲]

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See detailThe tropical sea anemone Aiptasia pallida as a lab model for the study of coral bleaching
Ladrière, Ophélie ULg; Roberty, Stéphane ULg; Baudesson, Charlotte et al

Poster (2008)

Bleaching is still among major events threatening coral reefs. New tools have to be developped to better understand the mechanisms leading to this pathology : we studied the use of the hermatypic anemone ... [more ▼]

Bleaching is still among major events threatening coral reefs. New tools have to be developped to better understand the mechanisms leading to this pathology : we studied the use of the hermatypic anemone Aiptasia pallida as experimental model for coral bleaching. Aiptasia appears as a good candidate as it is easy to maintain in aquarium and subjected to bleaching like corals. Both morphological and physiological approaches were performed to investigate the ultrastructure of the anemone tissues (TEM) and the zooxanthellae photophysiology (chlorophyll a fluorescence, respiration and pigmentation). Experiments under light and dark stress reveal that anemone tissues ultrastructure can be differently affected. In darkness, the ectoderm activity is reoriented to capture prey by increasing cnidocyte density. In contrast, intense light affects especially the gastroderm : intercellular spaces increase, the expulsion of intact algae in the gastric cavity and the degradation of zooxanthellae inside vacuoles seem to reduce the zooxanthellae density, chloroplast thylakoids lose their parallel arrangement. The analysis of the fluorescence induction curve appears as a powerful tool to analyse the physiological events series previous to bleaching. Although no significant zooxanthellae density reduction was observed, the decrease of pigments concentrations indicates that light or dark stresses induce anemone bleaching. Under strong light intensity, A. pallida zooxanthellae show an increased proportion of PSII QB non reducing, leading to partial photoinhibition. This phenomenon favours the ROS production that damages cellular structures of host and zooxanthellae. In darkness, there is no photosynthesis; anemones have therefore to find other feeding sources, as suggested by the ultrastructural approach. As the present results confirm some of those obtained on scleractinians, A. pallida can be regarded as a good model for coral bleaching studies and has numerous advantages for experimentation. [less ▲]

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