References of "Borges, Alberto"
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See detailUnderstanding the Black Sea ecosystem functioning during the eutrophication phase using mathematical modelling
Grégoire, Marilaure ULg; Capet, Arthur ULg; Barth, Alexander ULg et al

in Moncheva, Snejana (Ed.) Climate change in the Black Sea, hypthesis, observations, trends scenarios and mitigation strategy for the ecosystem (2008)

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See detailThe impact of lateral carbon fluxes on the European carbon balance
Ciais, P.; Borges, Alberto ULg; Abril, Gwenaël et al

in Biogeosciences (2008), 5

To date, little is known about the impact of processes which cause lateral carbon fluxes over continents, and from continents to oceans on the CO2 – and carbon budgets at local, regional and continental ... [more ▼]

To date, little is known about the impact of processes which cause lateral carbon fluxes over continents, and from continents to oceans on the CO2 – and carbon budgets at local, regional and continental scales. Lateral carbon fluxes contribute to regional carbon budgets as follows: Ecosystem CO2 sink=Ecosystem carbon accumulation+Lateral carbon fluxes. We estimated the contribution of wood and food product trade, of emission and oxidation of reduced carbon species, and of river erosion and transport as lateral carbon fluxes to the carbon balance of Europe (EU-25). The analysis is completed by new estimates of the carbon fluxes of coastal seas. We estimated that lateral transport (all processes combined) is a flux of 165 Tg C yr−1 at the scale of EU-25. The magnitude of lateral transport is thus comparable to current estimates of carbon accumulation in European forests. The main process contributing to the total lateral flux out of Europe is the flux of reduced carbon compounds, corresponding to the sum of non-CO2 gaseous species (CH4, CO, hydrocarbons, . . . ) emitted by ecosystems and exported out of the European boundary layer by the large scale atmospheric circulation. [less ▲]

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See detailCarbon dynamics in the highly eutrophicated Belgian Coastal Zone
Gypens, N.; Borges, Alberto ULg

in Current status of eutrophication in the Belgian coastal zone (2008)

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See detailCarbon biogeochemistry of the Betsiboka Estuary (north-western Madagascar)
Ralison, Olivier Harifidy; Borges, Alberto ULg; Dehairs, Frank et al

in Organic Geochemistry (2008), 39

Madagascar’s largest estuary (Betsiboka) was sampled along the salinity gradient during the dry season to document the distribution and sources of particulate and dissolved organic carbon (POC, DOC) as ... [more ▼]

Madagascar’s largest estuary (Betsiboka) was sampled along the salinity gradient during the dry season to document the distribution and sources of particulate and dissolved organic carbon (POC, DOC) as well as dissolved inorganic carbon (DIC). The Betsiboka was characterized by a relatively high suspended matter load, and in line with this, low DOC/POC ratios ( 0.4–2.5). The partial pressure of CO2 (pCO2) was generally above atmospheric equilibrium (270–1530 ppm), but relatively low in comparison to other tropical and subtropical estuaries, resulting in low average CO2 emission to the atmosphere (9.1 ± 14.2 mmol m 2 d 1). Despite the fact that C4 vegetation is reported to cover >80% of the catchment area, stable isotope data on DOC and POC suggest that C4 derived material comprises only 30% of both pools in the freshwater zone, increasing to 60–70% and 50–60%, respectively, in the oligohaline zone due to additional lateral inputs. Sediments from intertidal mangroves in the estuary showed low organic carbon concentrations (<1%) and d13C values (average 19.8‰) consistent with important inputs of riverine imported C4 material. This contribution was reflected in d13C signatures of bacterial phospholipid derived fatty acids (i + a15:0), suggesting the potential importance of terrestrial organic matter sources for mineralization and secondary production in coastal ecosystems. [less ▲]

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See detailEmission of CO2 and CH4 to the atmosphere by sediments and open waters in two Tanzanian mangrove forests
Kristensen, Erik; Flindt, Mogens R.; Ulomi, Shadrack et al

in Marine Ecology. Progress Series (2008)

Carbon gas balance was evaluated in an anthropogenically impacted (Mtoni) and a pristine (Ras Dege) mangrove forest in Tanzania. Exchange of carbon dioxide (CO2) was measured for inundated and air-exposed ... [more ▼]

Carbon gas balance was evaluated in an anthropogenically impacted (Mtoni) and a pristine (Ras Dege) mangrove forest in Tanzania. Exchange of carbon dioxide (CO2) was measured for inundated and air-exposed sediments during day and night using in situ and laboratory incubations. In situ methane (CH4) emissions were measured in the dark during air exposure only. Emission of CO2 and CH4 from open waters (e.g. creeks) was estimated from diurnal measurements of CO2, partial pressure (pCO2) and CH4 concentrations. CO2 emission from darkened sediments devoid of biogenic structures was comparable during inundation and air exposure (28 to 115 mmol m–2 d–1) with no differences between mangrove forests. Benthic primary production was low with only occasional net uptake of CO2 by the sediments. Emissions of CH4 from air-exposed sediment were generally 3 orders of magnitude lower than for CO2. Presence of pneumatophores and crab burrows increased low tide emissions several fold. Emissions from open waters were dependent on tidal level and wind speed. Lowest emission occurred during high tide (1 to 6 mmol CO2 m–2 d–1; 10 to 80 μmol CH4 m–2 d–1) and highest during low tide (30 to 80 mmol CO2 m–2 d–1; 100 to 350 μmol CH4 m–2 d–1) when supersaturated runoff from the forest floor and porewater seepage reached the creek water. Based on global average primary production and measured gas emissions, the carbon gas balance of the 2 mangrove forests was estimated. The densely vegetated Ras Dege forest appears to be an efficient sink of greenhouse carbon gases, while extensive clear-cutting at the Mtoni forest apparently has reduced its capacity to absorb CO2, although it is seemingly still a net sink for atmospheric CO2. [less ▲]

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See detailMangrove production and carbon sinks: a revision of global budget estimates
Bouillon, Steven; Borges, Alberto ULg; Castañeda-Moya, Edward et al

in Global Biogeochemical Cycles (2008), 22(GB2013),

Mangrove forests are highly productive but globally threatened coastal ecosystems, whose role in the carbon budget of the coastal zone has long been debated. Here we provide a comprehensive synthesis of ... [more ▼]

Mangrove forests are highly productive but globally threatened coastal ecosystems, whose role in the carbon budget of the coastal zone has long been debated. Here we provide a comprehensive synthesis of the available data on carbon fluxes in mangrove ecosystems. A reassessment of global mangrove primary production from the literature results in a conservative estimate of 218 ± 72 Tg C a 1. When using the best available estimates of various carbon sinks (organic carbon export, sediment burial, and mineralization), it appears that >50% of the carbon fixed by mangrove vegetation is unaccounted for. This unaccounted carbon sink is conservatively estimated at 112 ± 85 Tg C a 1, equivalent in magnitude to 30–40% of the global riverine organic carbon input to the coastal zone. Our analysis suggests that mineralization is severely underestimated, and that the majority of carbon export from mangroves to adjacent waters occurs as dissolved inorganic carbon (DIC). CO2 efflux from sediments and creek waters and tidal export of DIC appear to be the major sinks. These processes are quantitatively comparable in magnitude to the unaccounted carbon sink in current budgets, but are not yet adequately constrained with the limited published data available so far. [less ▲]

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See detailDissolved inorganic carbon dynamics in the waters surrounding forested mangroves of the Ca Mau Province (Vietnam)
Koné, J. M.; Borges, Alberto ULg

in Estuarine Coastal & Shelf Science (2008), 7(3), 409-421

Dissolved inorganic carbon (DIC) and ancillary data were obtained during the dry and rainy seasons in the waters surrounding two 10-yearold forested mangrove sites (Tam Giang and Kieˆn Va`ng) located in ... [more ▼]

Dissolved inorganic carbon (DIC) and ancillary data were obtained during the dry and rainy seasons in the waters surrounding two 10-yearold forested mangrove sites (Tam Giang and Kieˆn Va`ng) located in the Ca Mau Province (South-West Vietnam). During both seasons, the spatial variations of partial pressure of CO2 (pCO2) were marked, with values ranging from 704 ppm to 11481 ppm during the dry season, and from 1209 ppm to 8136 ppm during the rainy season. During both seasons, DIC, pCO2, total alkalinity (TAlk) and oxygen saturation levels (%O2) were correlated with salinity in the mangrove creeks suggesting that a combination of lower water volume and longer residence time (leading to an increase in salinity due to evaporation) enhanced the enrichment in DIC, pCO2 and TAlk, and an impoverishment in O2. The low O2 and high DIC and pCO2 values suggest that heterotrophic processes in the water column and sediments controlled these variables. The latter processes were meaningful since the high DIC and TAlk values in the creek waters were related to some extent to the influx of pore waters, consistent with previous observations. This was confirmed by the stochiometric relationship between TAlk and DIC that shows that anaerobic processes control these variables, although this approach did not allow identifying unambiguously the dominant diagenetic carbon degradation pathway. During the rainy season, dilution led to significant decreases of salinity, TAlk and DIC in both mangrove creeks and adjacent main channels. In the Kieˆn Va`ng mangrove creeks a distinct increase of pCO2 and decrease of %O2 were observed. The increase of TSM suggested enhanced inputs of organic matter probably from land surrounding the mangrove creeks, that could have led to higher benthic and water column heterotrophy. However, the flushing of water enriched in dissolved CO2 originating from soil respiration and impoverished in O2 could also have explained to some extent the patterns observed during the rainy season. Seasonal variations of pCO2 were more pronounced in the Kieˆn Va`ng mangrove creeks than in the Tam Giang mangrove creeks. The airewater CO2 fluxes were 5 times higher during the rainy season than during the dry season in the Kieˆn Va`ng mangrove creeks. In the Tam Giang mangrove creeks, the airewater CO2 fluxes were similar during both seasons. The airewater CO2 fluxes ranged from 27.1 mmol C m 2 d 1 to 141.5 mmol C m 2 d 1 during the dry season, and from 81.3 mmol m 2 d 1 to 154.7 mmol m 2 d 1 during the rainy season. These values are within the range of values previously reported in other mangrove creeks and confirm that the emission of CO2 from waters surrounding mangrove forests are meaningful for the carbon budgets of mangrove forests. [less ▲]

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See detailInter-annual variability of the carbon dioxide oceanic sink south of Tasmania
Borges, Alberto ULg; Tilbrook, B.; Metzl, N. et al

in Biogeosciences (2008), 5(1), 141-155

We compiled a large data-set from 22 cruises spanning from 1991 to 2003, of the partial pressure of CO2 (pCO(2)) in surface waters over the continental shelf (CS) and adjacent open ocean (43 degrees to 46 ... [more ▼]

We compiled a large data-set from 22 cruises spanning from 1991 to 2003, of the partial pressure of CO2 (pCO(2)) in surface waters over the continental shelf (CS) and adjacent open ocean (43 degrees to 46 degrees S; 145 degrees to 150 degrees E), south of Tasmania. Climatological seasonal cycles of pCO(2) in the CS, the subtropical zone (STZ) and the subAntarctic zone (SAZ) are described and used to determine monthly pCO(2) anomalies. These are used in combination with monthly anomalies of sea surface temperature (SST) to investigate inter-annual variations of SST and pCO(2). Monthly anomalies of SST (as intense as 2 degrees C) are apparent in the CS, STZ and SAZ, and are indicative of strong inter-annual variability that seems to be related to large-scale coupled atmosphere-ocean oscillations. Anomalies of pCO(2) normalized to a constant temperature are negatively related to SST anomalies. A reduced winter-time vertical input of dissolved inorganic carbon (DIC) during phases of positive SST anomalies, related to a poleward shift of westerly winds, and a concomitant local decrease in wind stress is the likely cause of the negative relationship between pCO(2) and SST anomalies. The observed pattern is an increase of the sink for atmospheric CO2 associated with positive SST anomalies, although strongly modulated by inter-annual variability of wind speed. Assuming that phases of positive SST anomalies are indicative of the future evolution of regional ocean biogeochemistry under global warming, we show using a purely observational based approach that some provinces of the Southern Ocean could provide a potential negative feedback on increasing atmospheric CO2. [less ▲]

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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)

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See detailInter-annual variability of the carbon dioxide oceanic sink south of Tasmania
Borges, Alberto ULg; Tilbrook, B.; Metzl, N. et al

Poster (2008)

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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 detailA dynamic model of an experimental bloom of coccolithophores Emiliania huxleyi
Joassin, Pascal ULg; Borges, Alberto ULg; Chou, Lei et al

Conference (2007, November 27)

A dynamic model has been developed to represent biogeochemical events observed during an experimentally induced bloom of coccolithophores Emiliania huxleyi. This bloom occurred in a mesocosm experiment ... [more ▼]

A dynamic model has been developed to represent biogeochemical events observed during an experimentally induced bloom of coccolithophores Emiliania huxleyi. This bloom occurred in a mesocosm experiment (Bergen 2001 experiment) during which ecosystem development was followed over a 23-days period through changes of the stocks of inorganic nutrients (nitrate, ammonium and phosphate), dissolved inorganic carbon and pCO2, O2 concentration, pigments, particulate organic carbon and nitrogen, dissolved organic carbon, the production of Transparent Exopolymeric Particles (TEP), primary production, alkalinity, calcification and particulate inorganic carbon. The dynamic model is based on unbalanced algal growth and balanced growth for bacteria as described in Van den Meersche et al. (2004). In addition, in order to adequately reproduce the observations, the model has been extended by including an explicit description of calcification, T.E.P production and an enhanced mortality due to viruses. This last process, based on a critical promiscuity between cellular hosts and viral agents, successfully contributed to reproduce the bloom extinction as observed in the mesocosm experiment. This model will be implemented in a coupled physical-biogeochemical model of the Black Sea ecosystem in the framework of the EU Sesame project and in the Gulf of Biscay in the frame of the Belgian PEACE project. [less ▲]

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See detailPlanktonic Archaea in Lake Kivu
Llirós, Marc; Darchambeau, François ULg; Plasencia, Anna et al

Conference (2007, September 02)

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See detailBiogeochemistry of a late coccolithophorid bloom at the continental margin of the Bay of Biscay
Harlay, Jérôme ULg; De Bodt, Caroline; d'Hoop, Quentin et al

Poster (2007, July 02)

Recent findings have led to growing concern regarding the impact of ocean acidification on marine calcifyers, but little is known about their biogeochemistry in natural (field) conditions (a major but ... [more ▼]

Recent findings have led to growing concern regarding the impact of ocean acidification on marine calcifyers, but little is known about their biogeochemistry in natural (field) conditions (a major but overlooked pre-requisite for realistic modelling of the future evolution of marine C cycling in a high CO2 world). The changes that will undergo these species in the near future and the biological feedback to decreasing oceanic pH are still open to debate. Coccolithophores, among which Emiliania huxleyi (Ehux) is the most abundant and widespread species, are the dominant calcifying phytoplankton in the subpolar and temperate zones of the worlds oceans. Within the framework of the Climate and Atmosphere Belgian Federal Science Policy Office programme, the continental margin of the Northern Bay of Biscay (North Atlantic Ocean) was visited in June 2006 during a transdisciplinary investigation of a late-spring bloom dominated by Ehux. Remote sensing images, transmitted onboard on a daily basis, were of valuable significance to pinpoint the coccolithophorid bloom along the margin, and to sample stations with contrasted biogeochemical properties.We determined 14C-based primary production and calcification rates, as well as pelagic respiration rates (O2 incubations). The magnitude of the biological and carbonate carbon fluxes will be synthesized and discussed in the light of biogeochemical parameters, such as Transparent Exopolymer Particles (TEP), chlorophyll-a, particulate carbon concentrations, particle dynamics and particulate organic carbon export (deduced from 234Th fluxes). Additional information on the bloom biogeochemistry will be presented (activity of dissolved esterase enzymes and bacterial community structure) to emphasize the importance of coccolithophorid blooms in the contemporary carbon cycle. [less ▲]

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