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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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See detailSeagrass production: linking individual, community and ecosystem carbon fluxes
Santos, R; Silva, J; Olivé, I et al

Conference (2013)

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See detailPhotoferrotrophy and Fe-cycling in a freshwater column
Llirós, M; Crowe, SA; García-Armisen, T et al

Poster (2013)

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See detailPhotoferrotrophy and Fe-cycling in a freshwater column
Llirós, M; Crowe, SA; García-Armisen, T et al

Conference (2013)

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See detailDynamics of dissolved inorganic carbon and aquatic metabolism in the Tana River basin, Kenya
Tamooh, F.; Borges, Alberto ULg; Meysman, F. J. R. et al

in Biogeosciences (2013), 10(11), 6911-6928

A basin-wide study was conducted in the Tana River basin (Kenya) in February 2008 (dry season), September–November 2009 (wet season) and June– July 2010 (end of the wet season) to assess the dynamics and ... [more ▼]

A basin-wide study was conducted in the Tana River basin (Kenya) in February 2008 (dry season), September–November 2009 (wet season) and June– July 2010 (end of the wet season) to assess the dynamics and sources of dissolved inorganic carbon (DIC) as well as to quantify CO2 fluxes, community respiration (R), and primary production (P). Samples were collected along the altitudinal gradient (from 3600 to 8 m) in several headwater streams, reservoirs (Kamburu and Masinga), and the Tana River mainstream. DIC concentrations ranged from 0.2 to 4.8 mmol L−1, with exceptionally high values (3.5±1.6 mmol L−1) in Nyambene Hills tributaries. The wide range of 13CDIC values (−15.0 to −2.4 ‰) indicate variable sources of DIC, with headwater streams recording more positive signatures compared to the Tana River mainstream. With with only a few exceptions, the entire riverine network was supersaturated in CO2, implying the system is a net source of CO2 to the atmosphere. pCO2 values were generally higher in the lower Tana River mainstream compared to headwater tributaries, opposite to the pattern typically observed in other river networks. This was attributed to high suspended sediment in the Tana River mainstream fuelling in-stream community respiration and net heterotrophy. This was particularly evident during the 2009 wet season campaign (median pCO2 of 1432 ppm) compared to the 2010 end of the wet season (1002 ppm) and 2008 dry season(579 ppm). First-order estimates show that in-stream community respiration was responsible for the bulk of total CO2 evasion (77 to 114 %) in the Tana River mainstream, while in the tributaries, this could only account for 5 to 68% of total CO2 evasion. This suggests that CO2 evasion in the tributaries was to a substantial degree sustained by benthic mineralisation and/or lateral inputs of CO2-oversaturated groundwater. While sediment loads increased downstream and thus light availability decreased in the water column, both chlorophyll a (0.2 to 9.6 μg L−1) and primary production (0.004 to 7.38 μmol CL−1 h−1) increased consistently downstream. Diurnal fluctuations of biogeochemical processes were examined at three different sites along the river continuum (headwater, reservoir and mainstream), and were found to be substantial only in the headwater stream, moderate in the reservoir and not detectable in the Tana River mainstream. The pronounced diurnal fluctuations observed in the headwater stream were largely regulated by periphyton as deduced from the low chlorophyll a in the water column. [less ▲]

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