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See detailL'astaxanthine: de la biologie à l'industrie
Fratamico, Anthony ULg

Scientific conference (2014, May 06)

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See detailStudy of the microbial flora of steak tartare by metagenomic approach
Korsak Koulagenko, Nicolas ULg; Delhalle, Laurent ULg; Nezer, Carine et al

Poster (2014, May 06)

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See detailHas oxygen depletion an impact on nutrients and macrofauna in a highly dynamic macrophytodetritus accumulation?
Remy, François ULg; Mascart, Thibaud ULg; Dauby, Patrick ULg et al

Poster (2014, May 06)

Posidonia oceanica is an endemic Mediterranean highly productive seagrass. Depending on the ability of the primary consumers to digest it alive, a generally important part of its foliar primary production ... [more ▼]

Posidonia oceanica is an endemic Mediterranean highly productive seagrass. Depending on the ability of the primary consumers to digest it alive, a generally important part of its foliar primary production falls in autumn, to decay inside the meadow or to be exported to sand patches to form “exported litter accumulations”. These accumulations are highly dynamic depending on hydrodynamics and seafloor geomorphology. Literature says that low O2 conditions might occur inside litter accumulations, but the annual oxygen dynamics or its impact on the litter-associated macrofauna has never been measured. We focused on 2 exported litter accumulations in Calvi Bay (Corsica), during 2 years for a total of 8 seasons. For each season, we collected water samples (n=6) from 3 different strata: Water Column (WC), Water Just Above the litter (WJA) and Water Inside the litter (WI). Oxygen was measured for each replicate using a Winkler-based automated routine for oxygen concentration measurements on micro-volumes. At the same time, nutrients concentrations (PO4, NH4, and NO2+NO3) were measured in WC, WJA and WI, but also in the Interstitial Water (IW) using a spectrophotometric continuous flow analyzer (adapted for low nutrients level in an oligotrophic environment). In parallel, macrofaunal (size >500µm) samples (n=3-6) were also collected, counted and identified to the specific level. Our results show significant differences between O2 concentrations/saturation from WI and the two other strata. Significant differences were detected between seasons, sites and years for WI which is the only stratum where really low O2 conditions can be observed. Significant differences were also detected between seasons for both WC and WJA but no differences between sites and years. On the other hand no significant differences were detected between WC and WJA. A similar observation was made for the nutrients at the annual, seasonal and spatial level. Moreover differences are also observed between the nutrients themselves. Our data shows no correlation between WI O2 concentrations and saturation, and global macrofauna abundance or biodiversity. Results are more contrasting at an individual specific level for the 4 most dominant species. For two amphipod species, Gammarella fucicola (55% of the global abundance) and Gammarus aequicauda, no significant correlations were detected between their abundance and O2. For the leptostracan species, Nebalia strausi, a significant negative correlation with O2 concentration was detected. For the last amphipod species, Melita hergensis, a significant positive correlation was observed. Our analyses also show significant correlations between WI O2 concentration/saturation, and WI / IW nutrients concentration. To conclude, this work shows that WI is a very particular and dynamic environment considering O2 concentration and saturation. Low O2 conditions can be observed in WI but never in WC or WJA showing that internal processes and relations with the sediment determine the O2 dynamics in WI and showing a potential “barrier” effect between WI and WC. Moreover O2 dynamics and its consequences may play a role in the nutrients dynamics and cycles. It is clear that faunal responses to low O2 conditions are not identifiable at a global community level. At a specific level, we show a more complex situation: some species do not seem to be impacted by low O2 conditions, but some present a significant positive, or a significant negative response. This shows the existence and complexity of species-dependent low O2 tolerance/adaptation, and the importance of a specific level data analyses to detect responses of dominant litter associated macro- invertebrates to O2 concentration and saturation variations. [less ▲]

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See detailLa Spiruline : a star is born (a long time ago)
de Marchin, Thomas ULg

Scientific conference (2014, May 06)

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See detailNew perspectives on probabilistic methods for nonlinear transient dynamics in civil engineering
Canor, Thomas ULg

Doctoral thesis (2014)

The objective of this thesis is to develop probabilistic methods to perform nonlinear transient analysis in civil engineering applications. The manuscript is divided into two parts. For large-dimensional ... [more ▼]

The objective of this thesis is to develop probabilistic methods to perform nonlinear transient analysis in civil engineering applications. The manuscript is divided into two parts. For large-dimensional structures subject to coherent random loads, an asymptotic expansion-based method is used to improve linear evolutionary spectral analysis. Then, this method is extended to equivalent statistical linearization by a multiple timescales approach. The second part of the thesis is focused on small-dimensional systems. It explores the solution of the Fokker-Planck equation with the smoothed particle hydrodynamics method. This meshless Lagrangian method particularly ensures the conservation and the positivity of the probability field. The accuracy and efficiency of both approaches are compared with Monte-Carlo simulations. [less ▲]

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See detailApprentissages et scolarité des primo-arrivants
Defays, Jean-Marc ULg

Conference given outside the academic context (2014)

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See detailIdentification et rôle des médiateurs sonores dans les phases de colonisation et d’installation de poissons dans un environnement corallien
Berten, Laetitia ULg

Doctoral thesis (2014)

La majorité des poissons de récifs coralliens présentent un cycle de vie complexe, caractérisé par une phase larvaire pélagique dispersive en milieu océanique, suivie d’une phase benthique au sein du ... [more ▼]

La majorité des poissons de récifs coralliens présentent un cycle de vie complexe, caractérisé par une phase larvaire pélagique dispersive en milieu océanique, suivie d’une phase benthique au sein du lagon ou sur la pente externe du récif. Ce travail porte sur l'influence du stimulus sonore lors de la colonisation et de l'installation, au sein du récif, des larves de poissons. De récentes études ont montré un effet attracteur du son de récifs sur les larves de poissons et de crustacés. Mais on ignore encore la distance à laquelle les larves sont capables de repérer le son du récif, ni si elles sont attirées par une signature spectrale complexe ou plus simplement par la présence d'un "bruit". Enfin, on ignore si les différents habitats d’un récif peuvent présenter des signatures acoustiques propres, ni si les sons des habitats peuvent guider les larves lors de leur installation au sein du récif. L'étude de mesures de pression sonore le long de trois transects de 2 km effectuées sur la côte nord de l'île de Moorea (Polynésie Française) met en évidence une diminution régulière de l'intensité sonore jusqu'à une distance à la crête de 750-1000 m. Au-delà de cette distance, et jusqu'à 2 km, une augmentation graduelle de la pression sonore est observée. Dès lors, une larve située à 750-1000 m du récif se retrouve confrontée à deux gradients de pression, l'un dirigés vers l'océan et l'autre vers le récif, et devra faire appel à d'autres stimuli pour s'orienter vers ce dernier. Au sein du récif, les sons provenant de 5 habitats de Moorea (crête interne, récif barrière, récif frangeant, chenal et mangrove) ont été étudiés. Les signatures sonores de chaque habitat (hormis crête interne et récif barrière) diffèrent des autres sur une certaine gamme de fréquences, et ces différences sont conservées avec la distance (plusieurs km). De plus, l'étude de l'influence des sons d'habitats et d'un son artificiel sur le comportement des larves met en évidence une modification du comportement chez 16 des 20 espèces testées. Les différentes réponses illustrent deux stratégies d'installation sur base du son: soit une sélection directe de l'habitat, soit un évitement de certains habitats, et donc une sélection "par défaut" des habitats restants. Pourtant, les niveaux de pression sonore des habitats du lagon sont sous les seuils de capacités sonores des juvéniles d'Abudefduf vaigiensis, Acanthurus triostegus, Chaetodon citrinellus, Rhinecanthus aculeatus et Myripristis kuntee. Ce paradoxe nous pousse à remettre en question l'utilisation de l'outil "ABR" (Auditory Brainstem Response) dans les études de perception et d'influence des sons sur le comportement des poissons. [less ▲]

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See detailPassive temperature tomography experiments to characterize transmissivity and connectivity of preferential flow paths in fractured media
Klepikova, Maria ULg

in Journal of Hydrology (2014)

The detection of preferential flow paths and the characterization of their hydraulic properties are major challenges in fractured rock hydrology. In this study, we propose to use temperature as a passive ... [more ▼]

The detection of preferential flow paths and the characterization of their hydraulic properties are major challenges in fractured rock hydrology. In this study, we propose to use temperature as a passive tracer to characterize fracture connectivity and hydraulic properties. In particular, we propose a new temperature tomography field method in which borehole temperature profiles are measured under different pumping conditions by changing successively the pumping and observation boreholes. To interpret these temperature-depth profiles, we propose a three step inversion-based framework. We consider first an inverse model that allows for automatic permeable fracture detection from borehole temperature profiles under pumping conditions. Then we apply a borehole-scale flow and temperature model to produce flowmeter profiles by inversion of temperature profiles. This second step uses inversion to characterize the relationship between temperature variations with depth and borehole flow velocities (Klepikova et al., 2011). The third inverse step, which exploits cross-borehole flowmeter tests, is aimed at inferring inter-borehole fracture connectivity and transmissivities. This multi-step inverse framework provides a means of including temperature profiles to image fracture hydraulic properties and connectivity. We test the proposed approach with field data obtained from the Ploemeur (N.W. France) fractured rock aquifer, where the full temperature tomography experiment was carried out between three 100 m depth boreholes 10 m apart. We identified several transmissive fractures and their connectivity which correspond to known fractures and corroborate well with independent information, including available borehole flowmeter tests and geophysical data. Hence, although indirect, temperature tomography appears to be a promising approach for characterizing connectivity patterns and transmissivities of the main flow paths in fractured rock. [less ▲]

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See detailMécanismes de concentration du carbone (CCMs) chez les algues
Gerin, Stéphanie ULg

Scientific conference (2014, May 06)

Description des mécanismes de concentration du carbone (CCMs) développés par les algues pour augmenter la disponibilité en CO2 dans l'environnement local de la RubisCO. De tels mécanismes permettent de ... [more ▼]

Description des mécanismes de concentration du carbone (CCMs) développés par les algues pour augmenter la disponibilité en CO2 dans l'environnement local de la RubisCO. De tels mécanismes permettent de limiter l'activité oxygénase de l'enzyme et d'atteindre la vitesse de catalyse maximale (Vmax). La présente communication se focalise particulièrement sur les CCMs biophysiques des cyanobactéries et de l'algue verte unicellulaire modèle Chlamydomonas reinhardtii. [less ▲]

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See detailCaractérisation des modes de consommation alimentaire des ménages à Kinshasa : analyse des interrelations entre modes de vie et habitudes alimentaires
Muteba Kalala, Damien ULg

Doctoral thesis (2014)

This study was initiated at the start of a hypothesis that households are in a situation of food insecurity when their lifestyles and livelihoods have changed or have not adapted and they have not the ... [more ▼]

This study was initiated at the start of a hypothesis that households are in a situation of food insecurity when their lifestyles and livelihoods have changed or have not adapted and they have not the ability to find a balance between a set of needs. Households’ food demand cannot be analyzed independently from all livelihoods and living conditions. For this study, a methodology based on household surveys was adopted. Based on their supposed wealth level, three districts were selected, the Residential Area in Limete, the Mabulu neighbourhood in Makala and Quarters I and VII in Ndjili. A sample of 346 households was selected. The results of the first survey on the characterization of households have achieved the first three objectives of the study. The second survey consisted of a household monitoring defined according to specific criteria. Thirty households were selected at the rate of 10 in each of three quarters. They were followed first during the dry season for three months, from June to August 2011, and subsequently in the rainy season for three months also between February and April 2012. The results of this study show among other things that food expenditures are much higher in the rainy season than in the dry season. However, the quantities consumed are relatively higher in the dry season than in the rainy season. The amount of food consumed per person per day was estimated in the dry season respectively at 1.202g (in the richest households), 833g (in average households) and 506g (in poor households). During the rainy season, quantities consumed are respectively of 1.120g (in the richest neighborhood), 801g (in the average households) and 493g (in less well-off households). Energy intake per person per day in the dry season is respectively 2571 calories (in the richest households), 1.864 calories (in average households) and 1,094 calories (in poor households). Energy intake was also lower in the rainy season. It reaches respectively 2.452 calories (in wealthy households), 1,838 calories (in average households) and 1,130 calories (in poor households). Protein intake per person per day was estimated in the dry season respectively at 102g (wealthier households), 81g (in average households) and 51g (in poor households). During the rainy season, these contributions are also low. They are around of 100g in the wealthier households, 80g in the average households and 50g in poor households. The analysis of different consumption patterns showed that the dietary habits of Kinshasa do not seem to meet the nutritional requirements. Considerations between the two parameters show that households are scarcely managing to find a balance. The evidence supporting this difficult balancing includes: food monotony in households, the tendency to promote the consumption of cheap food, food choices unrelated to dietary considerations, the appearance of more and more public health problems related to food consumption patterns. However, the dietary imbalance in Kinshasa households is not always linked to income. [less ▲]

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See detailHypoxia in macrophytodetritus accumulation: Species specific harpacticoid copepod adaptation?
Mascart, Thibaud ULg; De Troch, Marleen; Gobert, Sylvie ULg et al

Poster (2014, May 05)

Mediterranean Posidonia oceanica seagrass meadows generate high primary production and support large biodiversity of associated fauna and flora. The majority of the foliar material falls on the ... [more ▼]

Mediterranean Posidonia oceanica seagrass meadows generate high primary production and support large biodiversity of associated fauna and flora. The majority of the foliar material falls on the unvegetated sea floor during the autumnal leaf senescence, fuelling the detrital food web. Whilst laying on the sea floor the freshly formed macrophytodetritus pile up into accumulations according to the local hydrodynamics and seafloor geomorphology. In these litter accumulations, harpacticoid copepods (Crustacea, Copepoda) are the main meiofaunal players (metazoans in the size range of 38µm – 1mm) and show a high specific diversity. They are primarily grazers, but their high specific diversity suggests that they occupy also a large variety of trophic niches. This large morphological and trophic diversity can partly be promoted by the complexity of the phytodetritus in seagrass accumulations. On the other hand, macrophytodetritus degradation and flux of reduced compounds from the sediments is responsible for oxygen consumption inside the accumulation of seagrass litter. Therefore, concentration of oxygen inside the accumulation is very variable and often under the concentration observed in the water column just above the litter. Frequently, oxygen levels reach very low values. The present study aims to link the oxygen variability inside the accumulation to the densities of the five most dominant harpacticoid copepods found living in the P. oceanica litter. Standardized samples were collected seasonally in two contrasting sites of the Calvi Bay (Corsica) during one year. Our results showed no correlation between the oxygen concentrations and harpacticoid community diversity or their total abundances. The five most dominant species showed divergent results, but none had a clear correlation with the oxygen concentration. This contrasts with observation done for sediment meiofaunal community where most harpacticoid copepods are sensitive to oxygen level and where nematodes often dominate the community. This could be explained by their high mobility and the patchiness and variability of the oxygen concentrations present in the accumulations. Harpacticoid copepods, whilst being sensitive to hypoxia and anoxia developed a strategy to live in this fast oxygen changing environment. To conclude, our results underline the importance of species-specific analysis of correlation data. Especially in complex and dynamic environments where a variety of potential trophic niches are present and species competition is very likely to occur. The overall abundance pattern and diversity of the copepod community showed no relation to the oxygen concentration while the most abundant copepod species did not responded to fluctuating oxygen concentrations. [less ▲]

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See detailCorrelation between the acoustic noise field measured in a Posidonia oceanica bed and the photosynthetic activity
Felisberto, P; Zabel, F; Rodriguez, O et al

Poster (2014, May 05)

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See detailRates of microbial sulfur oxidation in low oxygen environments
Crowe, SA; Canfield, DE; Sturm, A et al

Poster (2014, May 05)

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See detailAmmonia Oxidising Archaea in the OMZ of a freshwater African Lake
Lliros, M; Ingeoglu, O; Garcia-Armisen, T et al

Poster (2014, May 05)

Detailed reference viewed: 21 (0 ULg)