Bioéthique

in Durand, Pascal (Ed.) Les Nouveaux Mots du Pouvoir. Abécédaire critique (2007)

Biofilms endodontiques et infections tardives des prothèses totales de hanche

in Revue Médicale de Liège (2007), 62(12), 736-42

Biofilms are well recognised in different settings. Endodontic biofilms containing bacteria responsible for bacteraemia and secondary infection of total hip arthroplasties (THA) represent a diagnostic ... [more ▼]

Biofilms are well recognised in different settings. Endodontic biofilms containing bacteria responsible for bacteraemia and secondary infection of total hip arthroplasties (THA) represent a diagnostic challenge because they are often asymptomatic. Their treatment is difficult and inadequate management of such unrecognised sources of systemic infection can lead to the devastating situation of an infected arthroplasty necessitating implant removal, long term antibiotic treatment and secondary implantation of a new prosthesis. Since about ten percent of secondary infected THA can have a dental origin, this article is intended to give guidelines to all intervening care providers: general practitioner, orthopaedic surgeon and dentist. [less ▲]

Bioformation ACORATA: Exploration biologique des pathologies osseuses

Conference given outside the academic context (2008)

Biogas (CO2, O-2, dimethylsulfide) dynamics in spring Antarctic fast ice

in Limnology and Oceanography (2007), 52(4), 1367-1379

We studied the temporal variations of CO2, O-2, and dimethylsulfide (DMS) concentrations within three environments (sea-ice brine, platelet ice-like layer, and underlying water) in the coastal area of ... [more ▼]

We studied the temporal variations of CO2, O-2, and dimethylsulfide (DMS) concentrations within three environments (sea-ice brine, platelet ice-like layer, and underlying water) in the coastal area of Adelie Land, Antarctica, during spring 1999 before ice breakup. Temporal changes were different among the three environments, while similar temporal trends were observed within each environment at all stations. The underlying water was always undersaturated in O-2 (around 85%) and oversaturated in CO2 at the deepest stations. O-2 concentrations increased in sea-ice brine as it melted, reaching oversaturation up to 160% due to the primary production by the sea-ice algae community (chlorophyll a in the bottom ice reached concentrations up to 160 mu g L-1 of bulk ice). In parallel, DMS concentrations increased up to 60 nmol L-1 within sea- ice brine and the platelet ice- like layer. High biological activity consumed CO2 and promoted the decrease of partial pressure of CO2 (pCO(2)). In addition, melting of pure ice crystals and calcium carbonate (CaCO3) dissolution promoted the shift from a state of CO2 oversaturation to a state of marked CO2 undersaturation (pCO(2) < 30 dPa). On the whole, our results suggest that late spring land fast sea ice can potentially act as a sink of CO2 and a source of DMS for the neighbouring environments, i.e., the underlying water or/ and the atmosphere. [less ▲]

Le biogaz, source d'énergie locale et internationale

Conference given outside the academic context (2010)

Le biogaz est une énergie renouvelable simple encore trop peu exploitée malgré les innombrables ressources en biomasse valorisables par cette filière. En Belgique, la méthanisation à la ferme utilise les ... [more ▼]

Le biogaz est une énergie renouvelable simple encore trop peu exploitée malgré les innombrables ressources en biomasse valorisables par cette filière. En Belgique, la méthanisation à la ferme utilise les déchets organiques des exploitations (lisier, fumier). Ceux-ci sont méthanisés pour produire du biogaz, valorisé en énergie électrique et chaleur, et du digestat, la fraction liquide, utilisé comme fertilisant. En Afrique, en plus d'être une source d'énergie, la méthanisation est utile dans le traitement des eaux usées. La valorisation des boues de vidange des fosses septiques pour produire du biogaz s'avère une solution pour nombre de villes africaines dont la gestion de ces boues n'est pas contrôlée et présente d'énormes risques sanitaires et environnementaux. Voici comment la méthanisation est une solution aux problèmes environnementaux et énergétiques dans divers pays, développés et en développement. [less ▲]

Biogeocehmical study of a coccolithophore bloom at the continental margin in the Northeast Atlantic

Conference (2005, June 14)

Coccolithophores, among which Emiliania huxleyi (Ehux) is the most abundant and widespread species, are the dominant calcifying phytoplankton in the temperate zone of the world’s oceans. The continental ... [more ▼]

Coccolithophores, among which Emiliania huxleyi (Ehux) is the most abundant and widespread species, are the dominant calcifying phytoplankton in the temperate zone of the world’s oceans. The continental margin in the Northern Bay of Biscay (North Atlantic Ocean) was visited in June 2004 during a multidisciplinary investigation of a late-spring bloom dominated by Ehux. Field sampling was assisted by daily transmission to the RV Belgica of remote sensing images, indicating the bloom development in the area. Primary production and calcification were measured by 14C incubations and zooplankton grazing experiments were performed. Vertical distributions of transparent exopolymer (TEP) concentration and bacterial density, as well as the bacterial production in surface waters, were also determined to elucidate the fate of biogenic carbonate production. The organic and inorganic carbon fluxes are evaluated in terms of relevant processes and discussed in relation with the DIC and nutrient dynamics. [less ▲]

Biogeochemical implications of calcification and secondary production of a population of the brittle star Acrocnida brachiata in a temperate coastal ecosystem

Poster (2004, May 10)

The production of organic matter and calcium carbonate by a population of the brittle star Acrocnida brachiata (Echinodermata) was calculated using demographic structure, population density, and relations ... [more ▼]

The production of organic matter and calcium carbonate by a population of the brittle star Acrocnida brachiata (Echinodermata) was calculated using demographic structure, population density, and relations between the size and the ash-free dry weight (AFDW) or the calcimass. During a two-year survey in the Bay of Seine (English Channel, France), one of the four major estuaries affecting the biogeochemical cycling of elements in the southern bight of the North Sea, benthic production of this species amounted to 40.3 g.m-2.yr-1 for AFDW and 80.0 g.m-2.yr-1 for CaCO3. Respiration, based on secondary production, was estimated to be 736 mmol CO2.m-2.yr-1. Using the molar ratio () of CO2 released to CaCO3 precipitated, this biogenic precipitation of calcium carbonate would result in an additional release of 617 mmol CO2.m-2.yr-1. The results of the present study demonstrate that marine calcification should be considered as a significant source of CO2 to seawater and thus a potential source of CO2 to the atmosphere, emphasizing the important role of the biomineralization and dissolution in the carbon budget of temperate coastal ecosystems. This additional biogenic source of CO2 could increase in the future in two ways: firstly, as a positive feedback of  to the rising pCO2 and, secondly, as a positive response to the availability of nutrients due to eutrophication. [less ▲]

Biogeochemical response of Emiliania huxleyi (PML B92/11) to elevated CO2 and temperature under phosphorous limitation: A chemostat study

in Journal of Experimental Marine Biology & Ecology (2011), 410

The present study investigates the combined effect of phosphorous limitation, elevated partial pressure of CO2 (pCO2) and temperature on a calcifying strain of Emiliania huxleyi (PML B92/11) by means of a ... [more ▼]

The present study investigates the combined effect of phosphorous limitation, elevated partial pressure of CO2 (pCO2) and temperature on a calcifying strain of Emiliania huxleyi (PML B92/11) by means of a fully controlled continuous culture facility. Two levels of phosphorous limitation were consecutively applied by renewal of culture media (N:P = 26) at dilution rates (D) of 0.3 d− 1 and 0.1 d− 1. CO2 and temperature conditions were 300, 550 and 900 μatm pCO2 at 14 °C and 900 μatm pCO2 at 18 °C. In general, the steady state cell density and particulate organic carbon (POC) production increased with pCO2, yielding significantly higher concentrations in cultures grown at 900 μatm pCO2 compared to 300 and 550 μatm pCO2. At 900 μatm pCO2, elevation of temperature as expected for a greenhouse ocean, further increased cell densities and POC concentrations. In contrast to POC concentration, C-quotas (pmol C cell− 1) were similar at D = 0.3 d− 1 in all cultures. At D = 0.1 d− 1, a reduction of C-quotas by up to 15% was observed in the 900 μatm pCO2 at 18 °C culture. As a result of growth rate reduction, POC:PON:POP ratios deviated strongly from the Redfield ratio, primarily due to an increase in POC. Ratios of particulate inorganic and organic carbon (PIC:POC) ranged from 0.14 to 0.18 at D = 0.3 d− 1, and from 0.11 to 0.17 at D = 0.1 d− 1, with variations primarily induced by the changes in POC. At D = 0.1 d− 1, cell volume was reduced by up to 22% in cultures grown at 900 μatm pCO2. Our results indicate that changes in pCO2, temperature and phosphorus supply affect cell density, POC concentration and size of E. huxleyi (PML B92/11) to varying degrees, and will likely impact bloom development as well as biogeochemical cycling in a greenhouse ocean. [less ▲]

Biogeochemical study of coccolithophorid blooms in the context of climate change

Doctoral thesis (2009)

Coccolithophores are unicellular microscopic algae (Haptophyta) surrounded by calcium carbonate plates that are produced during their life cycle. These species, whose contemporary contributor is Emiliania ... [more ▼]

Coccolithophores are unicellular microscopic algae (Haptophyta) surrounded by calcium carbonate plates that are produced during their life cycle. These species, whose contemporary contributor is Emiliania huxleyi, are mainly found in the sub-polar and temperate oceans, where they produce huge blooms visible from space. Coccolithophores are sensitive to ocean acidification that results from the ongoing accumulation of anthropogenic carbon dioxide (CO2) in the atmosphere. The response of these organisms to global change appears to be related to the reduction of their ability to produce calcium carbonate at the cellular level. At the community levels, one anticipates changes in the carbon fluxes associated to their blooms as calcification is reduced. However, the consequences of such environmental changes on this species are speculative and require improvements in the description of the mechanisms controlling the organic and inorganic carbon production and export. The first aspect of this work was to study the response of these organisms to artificially modified CO2 concentrations representative of the conditions occurring in the past (glacial) and those expected by the end of the century (2100). Two different levels were examined: the continuous monospecific cultures (chemostats) allowed us to work at the cellular level while the mesocosms gave light to the mechanisms taking place in an isolated fraction of the natural community. The second aspect of this work consisted of field studies carried out during four cruises (2002, 2003, 2004 and 2006) in the northern Bay of Biscay, where the occurrence of E. huxleyi blooms were observed in late spring. I describe the vertical profiles of biogeochemical variables (nutrients, chlorophyll-a, dissolved inorganic carbon chemistry, particulate carbon, transparent exopolymer particles (TEP)) and study processes such as primary production, calcification and bacterial production. The properties of these blooms are compared with those reported in the literature and enriched with original measurements such as the abundance and concentration of TEP that could play an important role in carbon export to the deep ocean, modifying the properties of the settling ballasted aggregates. [less ▲]

Biogeochemistry and carbon mass balance of a coccolithophore bloom in the northern Bay of Biscay (June 2006)

Poster (2013, May)

Primary production (PP), calcification (CAL), bacterial production (BP) and dark community respiration (DCR) were measured along with a set of various biogeochemical variables, in early June 2006, at ... [more ▼]

Primary production (PP), calcification (CAL), bacterial production (BP) and dark community respiration (DCR) were measured along with a set of various biogeochemical variables, in early June 2006, at several stations at the shelf break of the northern Bay of Biscay. The cruise was carried out after the main spring diatom bloom that, based on the analysis of a time-series of remotely sensed chlorophyll-a (Chl-a), peaked in mid-April. Remotely sensed sea surface temperature (SST) indicated the occurrence of enhanced vertical mixing (due to internal tides) at the continental slope, while adjacent waters on the continental shelf were stratified, as confirmed by vertical profiles of temperature acquired during the cruise. The surface layer of the stratified water masses (on the continental shelf) was depleted of inorganic nutrients. Dissolved silicate (DSi) levels probably did not allow significant diatom development. We hypothesize that mixing at the continental slope allowed the injection of inorganic nutrients that triggered the blooming of mixed phytoplanktonic communities dominated by coccolithophores (Emiliania huxleyi) that were favoured with regards to diatoms due to the low DSi levels. Based on this conceptual frame, we used an indicator of vertical stratification to classify the different sampled stations, and to reconstruct the possible evolution of the bloom from the onset at the continental slope (triggered by vertical mixing) through its development as the water mass was advected on-shelf and stratified. We also established a carbon mass balance at each station by integrating in the photic layer PP, CAL and DCR. This allowed computation at each station of the contribution of PP, CAL and DCR to CO2 fluxes in the photic layer, and how they changed from one station to another along the sequence of bloom development (as traced by the stratification indicator). This also showed a shift from net autotrophy to net heterotrophy as the water mass aged (stratified), and suggested the importance of extracellular production of carbon to sustain the bacterial demand in the photic and aphotic layers. [less ▲]