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See detailVariability of methane in the epilimnion of Lake Kivu
Borges, Alberto ULg; Abril, G.; Morana, C. et al

Poster (2012, April 22)

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See detailVariability of carbon dioxide and methane in the epilimnion of Lake Kivu
Borges, Alberto ULg; Bouillon, S.; Abril, G. et al

in Descy, J.-P.; Darchambeau, François; Schmid, M. (Eds.) Lake Kivu: Limnology and biogeochemistry of a tropical great lake (2012)

We report a dataset of the partial pressure of CO2 (pCO2) and me-thane concentrations (CH4) in the surface waters of Lake Kivu ob-tained during four cruises covering the two main seasons (rainy and dry ... [more ▼]

We report a dataset of the partial pressure of CO2 (pCO2) and me-thane concentrations (CH4) in the surface waters of Lake Kivu ob-tained during four cruises covering the two main seasons (rainy and dry). Spatial gradients of surface pCO2 and CH4 concentrations were modest in the main basin. In Kabuno Bay, pCO2 and CH4 concentra-tions in surface waters were higher, owing to the stronger influence of subaquatic springs from depth. Seasonal variations of pCO2 and CH4 in the main basin of Lake Kivu were strongly driven by deepen-ing of the epilimnion and the resulting entrainment of water charac-terized by higher pCO2 and CH4 concentrations. Physical and chem-ical vertical patterns in Kabuno Bay were seasonally stable, owing to a stronger stratification and smaller surface area inducing fetch limi-tation of wind driven turbulence. A global and regional cross-system comparison of pCO2 and CH4 concentrations in surface waters of lakes highlights the peculiarity of Kabuno Bay in terms of pCO2 values in surface waters. In terms of surface CH4 concentrations, both Kabuno Bay and the main basin of Lake Kivu are at the lower end of values in lakes globally, despite the huge amounts of CH4 and CO2 in the deeper layers of the lake. [less ▲]

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See detailSpatial and temporal CO2 exchanges measured by Eddy Covariance over a temperate intertidal flat and their relationships to net ecosystem production
Polsenaere, P.; Lamaud, E.; Lafon, V. et al

in Biogeosciences (2012), 9(1), 249--268

Measurements of carbon dioxide fluxes were performed over a temperate intertidal mudflat in southwestern France using the micrometeorological Eddy Covariance (EC) technique. EC measurements were carried ... [more ▼]

Measurements of carbon dioxide fluxes were performed over a temperate intertidal mudflat in southwestern France using the micrometeorological Eddy Covariance (EC) technique. EC measurements were carried out in two contrasting sites of the Arcachon flat during four periods and in three different seasons (autumn 2007, summer 2008, autumn 2008 and spring 2009). In addition, satellite images of the tidal flat at low tide were used to link the net ecosystem CO2 exchange (NEE) with the occupation of the mudflat by primary producers, particularly by Zostera noltii meadows. CO2 fluxes during the four deployments showed important spatial and temporal variations, with the flat rapidly shifting from sink to source with the tide. Absolute CO2 fluxes showed generally small negative (influx) and positive (efflux) values, with larger values up to −13 μmol m−2 s−1 for influxes and 19 μmol m−2 s−1 for effluxes. Low tide during the day was mostly associated with a net uptake of atmospheric CO2. In contrast, during immersion and during low tide at night, CO2 fluxes where positive, negative or close to zero, depending on the season and the site. During the autumn of 2007, at the innermost station with a patchy Zostera noltii bed (cover of 22 ± 14% in the wind direction of measurements), CO2 influx was −1.7 ± 1.7 μmol m−2 s−1 at low tide during the day, and the efflux was 2.7 ± 3.7 μmol m−2 s−1 at low tide during the night. A gross primary production (GPP) of 4.4 ± 4.1 μmol m−2 s−1 during emersion could be attributed to microphytobenthic communities. During the summer and autumn of 2008, at the central station with a dense eelgrass bed (92 ± 10%), CO2 uptakes at low tide during the day were −1.5 ± 1.2 and −0.9 ± 1.7 μmol m−2 s−1, respectively. Night time effluxes of CO2 were 1.0 ± 0.9 and 0.2 ± 1.1 μmol m−2 s−1 in summer and autumn, respectively, resulting in a GPP during emersion of 2.5 ± 1.5 and 1.1 ± 2.0 μmol m−2 s−1, respectively, attributed primarily to the seagrass community. At the same station in April 2009, before Zostera noltii started to grow, the CO2 uptake at low tide during the day was the highest (−2.7 ± 2.0 μmol m−2 s−1). Influxes of CO2 were also observed during immersion at the central station in spring and early autumn and were apparently related to phytoplankton blooms occurring at the mouth of the flat, followed by the advection of CO2-depleted water with the flooding tide. Although winter data as well as water carbon measurements would be necessary to determine a precise CO2 budget for the flat, our results suggest that tidal flat ecosystems are a modest contributor to the CO2 budget of the coastal ocean. [less ▲]

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See detailVariability of methane in the epilimnion of Lake Kivu
Borges, Alberto ULg; Abril, G.; Delille, Bruno ULg et al

Poster (2011, April 08)

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See detailSeasonal variability of methane in the rivers and lagoons of Ivory Coast (West Africa)
Kone, Y. J. M.; Abril, G.; Delille, Bruno ULg et al

in Biogeochemistry (2010), 100(1-3), 21-37

We report a data-set of dissolved methane (CH4) in three rivers (Como,, Bia and Tano,) and five lagoons (Grand-Lahou, Ebri,, Potou, Aby and Tendo) of Ivory Coast (West Africa), during the four main ... [more ▼]

We report a data-set of dissolved methane (CH4) in three rivers (Como,, Bia and Tano,) and five lagoons (Grand-Lahou, Ebri,, Potou, Aby and Tendo) of Ivory Coast (West Africa), during the four main climatic seasons (high dry season, high rainy season, low dry season and low rainy season). The surface waters of the three rivers were over-saturated in CH4 with respect to atmospheric equilibrium (2221-38719%), and the seasonal variability of CH4 seemed to be largely controlled by dilution during the flooding period. The strong correlation of CH4 concentrations with the partial pressure of CO2 (pCO(2)) and dissolved silicate (DSi) confirm the dominance of a continental sources (from soils) for both CO2 and CH4 in these rivers. Diffusive air-water CH4 fluxes ranged between 25 and 1187 mu mol m(-2) day(-1), and annual integrated values were 288 +/- A 107, 155 +/- A 38, and 241 +/- A 91 mu mol m(-2) day(-1) in the Como,, Bia and Tano, rivers, respectively. In the five lagoons, surface waters were also over-saturated in CH4 (ranging from 1496 to 51843%). Diffusive air-water CH4 fluxes ranged between 20 and 2403 mu mol m(-2) day(-1), and annual integrated values were 78 +/- A 34, 338 +/- A 217, 227 +/- A 79, 330 +/- A 153 and 326 +/- A 181 mu mol m(-2) day(-1) in the Grand-Lahou, Ebri,, Potou, Aby and Tendo lagoons, respectively. The largest CH4 over-saturations were observed in the Tendo and Aby lagoons that are permanently stratified systems (unlike the other three lagoons), leading to anoxic bottom waters favorable for a large CH4 production. In addition, these two stratified lagoons showed low pCO(2) values due to high primary production, which suggests an efficient transfer of organic matter across the pycnocline. As a result, the stratified Tendo and Aby lagoons were respectively, a low source of CO2 to the atmosphere and a sink of atmospheric CO2 while the other three well-mixed lagoons were strong sources of CO2 to the atmosphere but less over-saturated in CH4. [less ▲]

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See detailCarbon dioxide and methane dynamics in estuaries
Borges, Alberto ULg; Abril, G.

Conference (2010)

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See detailSeasonal variability of carbon dioxide and methane in the rivers and lagoons of Ivory Coast (West Africa)
Koné, Y.J.M.; Abril, G.; Delille, Bruno ULg et al

Poster (2009, May)

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See detailDistribution, origin and cycling of carbon in the Tana River (Kenya): a dry season basin-scale survey from headwaters to the delta
Bouillon, S.; Abril, G.; Borges, Alberto ULg et al

in Biogeosciences (2009), 6

The Tana River basin (TRB) is the largest in Kenya (_120 000 km2). We conducted a survey during the dry season throughout the TRB, analyzing a broad suite of biogeochemical parameters. Biogeochemical ... [more ▼]

The Tana River basin (TRB) is the largest in Kenya (_120 000 km2). We conducted a survey during the dry season throughout the TRB, analyzing a broad suite of biogeochemical parameters. Biogeochemical signatures in headwater streams were highly variable. Along the middle and lower river course, total suspended matter (TSM) concentrations increased more than 30-fold despite the absence of tributary inputs, indicating important resuspension events of internally stored sediment. These resuspended sediment inputs were characterized by a lower and 14C-depleted OC content, suggesting selective degradation of more recent material during sediment retention. Masinga Dam (a large reservoir on the upper river) induced a strong nutrient retention (_50% for inorganic N, _72% for inorganic phosphate, and _40% for dissolved silicate). Moreover, while DOC pools and _13C signatures were similar above, in and below the reservoir, the POC pool in Masinga surface waters was dominated by 13C-depleted phytoplankton, which contributed to the riverine POC pool immediately below the dam, but rapidly disappeared further downstream, suggesting rapid remineralization of this labile C pool in the river system. Despite the generally high turbidity, the combination of relatively high oxygen saturation levels, low _18O signatures of dissolved O2 (all <+24.2‰), and the relatively low pCO2 values suggest that in-stream primary production was significant, even though pigment data suggest that phytoplankton makes only a minor contribution to the total POC pool in the Tana River. [less ▲]

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See detailCarbon cycling in the mixolimnion of Lake Kivu (East Africa)
Borges, Alberto ULg; Descy, J.-P.; Delille, Bruno ULg et al

Poster (2009)

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See detailSeasonal variability of carbon dioxide and methane in the rivers and lagoons of Ivory Coast (West Africa)
Koné, Y. J. M.; Abril, G.; Delille, Bruno ULg et al

Poster (2009)

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See detailCarbon cycling in the mixolimnion of Lake Kivu (East Africa)
Borges, Alberto ULg; Descy, J.-P.; Delille, Bruno ULg et al

Conference (2009)

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See detailCarbon cycling in the mixolimnion of Lake Kivu (East Africa)
Borges, Alberto ULg; Descy, J.-P.; Delille, Bruno ULg et al

Poster (2009)

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See detailCarbon dioxide dynamics in lake Kivu during the dry and wet seasons
Borges, Alberto ULg; Delille, Bruno ULg; Descy, J.-P. et al

Poster (2008, April)

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See detailSeasonal variability of CO2 fluxes in the tropical lagoons of Ivory Coast
Koné, Y. J. M.; Gourene, G.; Abril, G. et al

Poster (2008)

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See detailCarbon dioxide in European coastal waters
Borges, Alberto ULg; Schiettecatte, L.-S.; Abril, G. et al

Poster (2007, March)

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See detailCarbon dioxide in European coastal waters
Borges, Alberto ULg; Schiettecatte, L.-S.; Abril, G. et al

Poster (2007)

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See detailCarbon dioxide in European coastal waters
Borges, Alberto ULg; Schiettecatte, L.-S.; Abril, G. et al

Poster (2006)

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See detailCarbon dioxide and methane emissions from estuaries
Abril, G.; Borges, Alberto ULg

in Greenhouse gases emissions from natural environments and hydroelectric reservoirs: fluxes and processes (2005)

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See detailGas transfer velocities of CO2 in three European estuaries (Randers Fjord, Scheldt and Thames)
Borges, Alberto ULg; Delille, Bruno ULg; Schiettecatte, L. S. et al

Poster (2003, April)

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