References of "Borges, Alberto"
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See detailSources, transport et transformation du carbone, de l’azote et du phosphore dans le fleuve Niger : résultats après 2 années d’observations à Niamey
Alhou, Bassirou; Darchambeau, François ULg; Bouillon, Steven et al

Conference (2013, December 05)

Le fleuve Niger est le troisième plus important fleuve d'Afrique et draine une superficie d'environ 2 120 000 km². Il englobe six régions hydrographiques caractéristiques des écosystèmes de l’Afrique ... [more ▼]

Le fleuve Niger est le troisième plus important fleuve d'Afrique et draine une superficie d'environ 2 120 000 km². Il englobe six régions hydrographiques caractéristiques des écosystèmes de l’Afrique occidentale. Nonobstant l’importance de ce fleuve à l’échelle régionale et continentale, peu de données ont été récemment collectées sur la biogéochimie du fleuve et en particulier sur son rôle dans le transport et la transformation de la matière, dont le carbone, l’azote et le phosphore. La présente communication traite des résultats d’un suivi sur deux années, d’avril 2011 à mars 2013 dans le Niger moyen, en amont de la ville de Niamey (Niger) [2.01° E, 13.57° N], selon une fréquence d’observation bihebdomadaire. Les variables mesurées sont la température, la conductivité, l’oxygène dissous, le pH, la matière en suspension (MES), l’alcalinité totale (TA), les différentes formes du carbone (C), de l’azote (N) et du phosphore (P) inorganiques dissous, le C, l’N et le P organiques particulaires, ainsi que la composition isotopique de ces éléments. Une attention particulière est portée aux concentrations des gaz à effet de serre (GES) que sont le dioxyde de carbone (CO2), le méthane (CH4) et l’hémioxide d’azote (N2O). Les débits journaliers du fleuve proviennent de la station de mesure hydrologique de l’autorité du Bassin du Niger (ABN) à Niamey. Les flux annuels ont été calculés par la méthode de Beale pour les régimes stratifiés (Gumleaf v0.1) à partir des débits quotidiens et des concentrations observées. La situation hydrologique a été fort contrastée entre les 2 années d’étude puisque le débit moyen sur la première année était de seulement 674 m3 s-1, soit un des débits les plus faibles enregistrés sur le fleuve à Niamey depuis 1940, et de 1096 m3 s-1, soit une valeur médiane, lors de la deuxième année. Nos résultats montrent que la MES, le carbone organique particulaire, le carbone organique dissous et le carbone inorganique dissous sont principalement transportés lors de la crue locale, engendrée par les précipitations de la mousson en juillet-août. La seconde crue, ou crue guinéenne, qui a lieu de novembre à janvier, est caractérisée par une chute des températures et des eaux claires. Les flux annuels des différentes espèces transportées étaient en relation directe avec les différences de régime hydrologique. [less ▲]

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See detailContribution to the description of the nitrogen cycle in Lake Kivu
Roland, Fleur ULg; Borges, Alberto ULg; Crowe, Sean et al

Poster (2013, November 12)

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See detailLake Kivu: food web structure and energy flows
Descy, J-P; Sarmento, H; Isumbisho, P et al

Conference (2013, August 04)

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See detailCoccolithophore blooms in the Bay of Biscay: Results from the PEACE project
Harlay, Jérôme ULg; Chou, Lei; Sabbe, Koen et al

Conference (2013, May 15)

Pelagic and benthic processes were determined in the nothern Bay of Biscay when coccolithophores blooms occured between 2006 and 2008. Here we present a synthesis of pelagic primary production ... [more ▼]

Pelagic and benthic processes were determined in the nothern Bay of Biscay when coccolithophores blooms occured between 2006 and 2008. Here we present a synthesis of pelagic primary production, calcification and respiration and benthic respiration and dissolution of CaCO3. Or results suggest that CaCO3 dissolution in the surface sediments is small (~1%) compared to integrated pelagic calcification. Benthic respiration increases with the organic load of the sediment and represents ~8% of the integrated pelagic respiration. The relationship between dissolution and respiration rates suggests a metabolic driven dissolution in waters supersaturated with respect to calcite (omega>3.5). We address a mass balance of the described processes and associated CO2 fluxes in the water column. [less ▲]

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See detailThe influence of biogeochemical processes on the pH dynamics in the seasonally hypoxic saline Lake Grevelingen, The Netherlands
Hagens, M; Slomp, C; Meysman, F et al

Poster (2013, May 07)

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See detailBiogeochemistry and carbon mass balance of a coccolithophore bloom in the northern Bay of Biscay (June 2006)
Harlay, Jérôme ULg; Chou, Lei; Van Oostende, Nicolas et al

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 ▲]

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See detailVariability of North Sea pH and CO2 pumping in response to North Atlantic Oscillation forcing
Salt, L; Thomas, H; Prowe, F et al

Poster (2013, April 07)

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See detailThe influence of biogeochemical processes on the pH dynamics in the seasonally hypoxic saline Lake Grevelingen
Hagens, M; Slomp, C; Meysman, F et al

Poster (2013, April 07)

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See detailFrom a source to a sink: the role of biological activities on atmospheric CO2 exchange along the river-ocean continuum
Gypens, N; Passy, P; Lancelot, C et al

Poster (2013, April 07)

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