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See detailDissolved inorganic carbon dynamics in the Gulf of Biscay (June 2006)
Suykens, K.; Delille, Bruno ULg; Borges, Alberto ULg

Poster (2007)

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See detailCarbon dioxide dynamics in the tropical Ebrié lagoon (Ivory Coast)
Koné, Y. J. M.; Delille, Bruno ULg; Borges, Alberto ULg

Poster (2007)

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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, Gwenaël et al

in Estuarine Coastal & Shelf Science (2006), 70(3), 375-387

We compiled from literature annually integrated air-water fluxes of carbon dioxide (CO2) computed from field measurements, in 20 coastal European environments that were gathered into 3 main ecosystems ... [more ▼]

We compiled from literature annually integrated air-water fluxes of carbon dioxide (CO2) computed from field measurements, in 20 coastal European environments that were gathered into 3 main ecosystems: inner estuaries, upwelling continental shelves and non-upwelling continental shelves. The comparison of annual cycles of the partial pressure of CO2 (pCO(2)) in 5 contrasting continental shelves provided insights into the biogeochemical drivers of the CO2 fluxes. The latter were also investigated by comparing CO2 fluxes to net ecosystem (NEP) and net community production (NCP) in 3 contrasted coastal ecosystems. Air-water CO2 fluxes were scaled at European regional level and compared to fluxes of atmospheric CO2 in other aquatic and terrestrial compartments. Continental shelves are significant sinks for atmospheric CO2 at an average rate of -1.9 molC m(-2) yr(-1) that scaled at European level corresponds to an absorption of atmospheric CO2 of -68.1 TgC yr(-1). This sink is equivalent to the one reported for the terrestrial biosphere of -66.1 TgC yr(-1), based on carbon-stock change models. Estuaries are significant sources of CO2 to the atmosphere at an average rate of 49.9 molC m(-2) yr(-1) that is higher than the CO2 emission to the atmosphere from rivers, streams and lakes. The scaled emission of CO2 to the atmosphere from inner estuaries of about 67.0 TgC yr(-1) would almost fully balance the sink of atmospheric CO2 computed for continental shelves. However, the scaled emission of CO2 from estuaries to the atmosphere is inconsistent with the potential emission of CO2 based on the fate of river organic carbon during estuarine transit. This discrepancy is most probably due to the poorly constrained surface area estimate of inner estuaries. (c) 2006 Elsevier Ltd. All rights reserved. [less ▲]

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See detailCO2 deposition over the multi-year ice of the western Weddell Sea
Zemmelink, H. J.; Delille, Bruno ULg; Tison, J. L. et al

in Geophysical Research Letters (2006), 33(13),

Field measurements by eddy correlation (EC) indicate an average uptake of 0.6 g CO2 m(-2) d(-1) by the ice-covered western Weddell Sea in December 2004. At the same time, snow that covers ice floes of the ... [more ▼]

Field measurements by eddy correlation (EC) indicate an average uptake of 0.6 g CO2 m(-2) d(-1) by the ice-covered western Weddell Sea in December 2004. At the same time, snow that covers ice floes of the western Weddell Sea becomes undersaturated with CO2 relative to the atmosphere during early summer. Gradients of CO2 from the ice to the atmosphere do not support significant diffusive fluxes and are not strong enough to explain the observed CO2 deposition. We hypothesize that the transport of air through the snow pack is controlled by turbulence and that undersaturation of CO2 is caused by biological productivity at the ice-snow and snow-atmosphere interface. The total carbon uptake by the multi-year ice zone of the western Weddell Sea in December could have been as high as 6.6 Tg C y(-1). [less ▲]

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See detailOutils de biorestauration des sols sub-antarctiques exposés aux hydrocarbures pétroliers
Delille, D.; Pelletier, E.; Coulon, F. et al

in carn (2006), 21

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See detailVariability of the net air-sea CO2 flux inferred from shipboard and satellite measurements in the Southern Ocean south of Tasmania and New Zealand
Rangama, Y.; Boutin, J.; Etcheto, J. et al

in Journal of Geophysical Research. Oceans (2005), 110(C9),

We determine the distribution of oceanic CO2 partial pressure (pCO(2)) with respect to remotely sensed parameters (sea surface temperature (SST) and chlorophyll (Chl)) in order to gain an understanding of ... [more ▼]

We determine the distribution of oceanic CO2 partial pressure (pCO(2)) with respect to remotely sensed parameters (sea surface temperature (SST) and chlorophyll (Chl)) in order to gain an understanding of the small-scale (10-100 km) pCO(2) variability and to estimate the net air-sea CO2 flux in the region (125 degrees E-205 degrees E; 45 degrees S-60 degrees S), which represents 22% of the Southern Ocean area between 45 degrees S and 60 degrees S. We split the study area into several biogeochemical provinces. In chlorophyll-poor regions, pCO(2) is negatively correlated with SST, indicating that pCO(2) is mostly controlled by mixing processes. For Chl > 0.37 mg m(-3), pCO(2) is negatively correlated with Chl, indicating that pCO(2) variability is mostly controlled by carbon fixation by biological activity. We deduce fields of pCO(2) and of air-sea CO2 fluxes from satellite parameters using pCO(2)-SST, pCO(2)-chlorophyll relationships and air-sea gas exchange coefficient, K, from satellite wind speed. We estimate an oceanic CO2 sink from December 1997 to December 1998 of -0.08 GtC yr(-1) with an error of 0.03 GtC yr(-1). This sink is approximately 38% smaller than that computed from the Takahashi et al. (2002) climatological distribution of Delta pCO(2) for the 1995 year but with the same K (-0.13 GtC yr(-1)). When we correct ocean pCO(2) for the interannual variability between 1995 and 1998, the difference is even larger, and we cannot reconcile both estimates in February-March and from June to November. This strengthens the need of new in situ measurements for validating extrapolation methods and for improving knowledge of interannual pCO(2) variability. [less ▲]

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See detailBudgeting sinks and sources of CO2 in the coastal ocean: Diversity of ecosystems counts
Borges, Alberto ULg; Delille, Bruno ULg; Frankignoulle, M.

in Geophysical Research Letters (2005), 32(14),

Air-water CO2 fluxes were up-scaled to take into account the latitudinal and ecosystem diversity of the coastal ocean, based on an exhaustive literature survey. Marginal seas at high and temperate ... [more ▼]

Air-water CO2 fluxes were up-scaled to take into account the latitudinal and ecosystem diversity of the coastal ocean, based on an exhaustive literature survey. Marginal seas at high and temperate latitudes act as sinks of CO2 from the atmosphere, in contrast to subtropical and tropical marginal seas that act as sources of CO2 to the atmosphere. Overall, marginal seas act as a strong sink of CO2 of about -0.45 Pg C yr(-1). This sink could be almost fully compensated by the emission of CO2 from the ensemble of near-shore coastal ecosystems of about 0.40 Pg C yr(-1). Although this value is subject to large uncertainty, it stresses the importance of the diversity of ecosystems, in particular near-shore systems, when integrating CO2 fluxes at global scale in the coastal ocean. [less ▲]

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See detailResponse of primary production and calcification to changes of pCO(2) during experimental blooms of the coccolithophorid Emiliania huxleyi
Delille, Bruno ULg; Harlay, Jérôme ULg; Zondervan, Ingrid et al

in Global Biogeochemical Cycles (2005), 19(2),

[1] Primary production and calcification in response to different partial pressures of CO2 (PCO2) ("glacial,'' "present,'' and "year 2100'' atmospheric CO2 concentrations) were investigated during a ... [more ▼]

[1] Primary production and calcification in response to different partial pressures of CO2 (PCO2) ("glacial,'' "present,'' and "year 2100'' atmospheric CO2 concentrations) were investigated during a mesocosm bloom dominated by the coccolithophorid Emiliania huxleyi. The day-to-day dynamics of net community production (NCP) and net community calcification (NCC) were assessed during the bloom development and decline by monitoring dissolved inorganic carbon (DIC) and total alkalinity ( TA), together with oxygen production and 14 C incorporation. When comparing year 2100 with glacial PCO2 conditions we observed: ( 1) no conspicuous change of net community productivity (NCPy); ( 2) a delay in the onset of calcification by 24 to 48 hours, reducing the duration of the calcifying phase in the course of the bloom; ( 3) a 40% decrease of NCC; and ( 4) enhanced loss of organic carbon from the water column. These results suggest a shift in the ratio of organic carbon to calcium carbonate production and vertical flux with rising atmospheric PCO2. [less ▲]

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See detailBarium distribution across the Southern Ocean frontal system in the Crozet-Kerguelen Basin
Jacquet, S. H. M.; Dehairs, F.; Cardinal, D. et al

in Marine Chemistry (2005), 95(3-4), 149-162

We investigated the dissolved and excess particulate Ba distribution (Ba-xs, an estimate of biogenic Ba considered to consist mainly of barite [BaSO4]) across the complex frontal system of the Crozet ... [more ▼]

We investigated the dissolved and excess particulate Ba distribution (Ba-xs, an estimate of biogenic Ba considered to consist mainly of barite [BaSO4]) across the complex frontal system of the Crozet-Kerguelen Basin (Southern Ocean; 42-47 degrees S, 62-65 degrees E). Ba-xs profiles show the characteristic mesopelagic maximum (depth range between 150 and 400 in) reaching up to 1000 pM in the Subantarctic Zone and Subtropical Front, the highest value observed for Southern Ocean mesopelagic waters. Dissolved Ba (concentrations between 38 and 104 nM) correlates with silicate and alkalinity, but the regression is not perfect, reflecting the involvement of different biogenic carriers in the control of the water column distribution of these compounds. Dissolved Ba in the upper 500 in appears strongly influenced by cross-frontal exchanges, involving both northward and southward transport of water masses. In the mesopelagic waters (150-400 m) of the Polar Front Zone, a dissolved Ba depletion faces the Ba, maximum. This depletion appears mainly maintained by cross-frontal advection of waters containing less Ba and originating north of the Subantarctic Front. Overall, no clear evidence that precipitation of barite reflected by the occurrence of Baxs maxima does measurably influence the distribution of dissolved Ba was found. (C) 2004 Elsevier B.V. All rights reserved. [less ▲]

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See detailTesting the direct effect of CO2 concentration on a bloom of the coccolithophorid Emiliania huxleyi in mesocosm experiments
Engel, Anja; Zondervan, Ingrid; Aerts, Katrien et al

in Limnology and Oceanography (2005), 50(2), 493-507

We studied the direct effects of CO, and related changes in seawater carbonate chemistry on marine planktonic organisms in a mesocosm experiment. In nine outdoor enclosures (similar to 11 m(3) each), the ... [more ▼]

We studied the direct effects of CO, and related changes in seawater carbonate chemistry on marine planktonic organisms in a mesocosm experiment. In nine outdoor enclosures (similar to 11 m(3) each), the partial pressure of CO2 (pCO(2)) in the seawater was modified by an aeration system. The triplicate mesocosm treatments represented low (similar to 190 parts per million by volume (ppmV) CO2), present (similar to 410 ppmV CO2), and high (similar to 710 ppmV CO2) pCO(2) conditions. After initial fertilization with nitrate and phosphate a bloom dominated by the coccolithophorid Emiliania huxleyi occurred simultaneously in all of the nine mesocosms; it was monitored over a 19-day period, The three CO2 treatments assimilated nitrate and phosphate similarly. The concentration of particulate constituents was highly variable among the replicate mesocosms, disguising direct CO2-related effects. Normalization of production rates within each treatment, however, indicated that the net specific growth rate of E. huxleyi, the rate of calcification per cell, and the elemental stoichiometry of uptake and production processes were sensitive to changes in pCO(2). This broad influence of CO2 on the E huxleyi bloom suggests that changes in CO2 concentration directly affect cell physiology with likely effects on the marine biogeochemistry. [less ▲]

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See detailWhole-system metabolism and CO2 fluxes in a Mediterranean Bay dominated by seagrass beds (Palma Bay, NW Mediterranean)
Gazeau, Frédéric; Duarte, C. M.; Gattuso, Jean-Pierre et al

in Biogeosciences (2005), 2(1), 43-60

Planktonic and benthic incubations (bare and Posidonia oceanica vegetated sediments) were performed at monthly intervals from March 2001 to October 2002 in a seagrass vegetated area of the Bay of Palma ... [more ▼]

Planktonic and benthic incubations (bare and Posidonia oceanica vegetated sediments) were performed at monthly intervals from March 2001 to October 2002 in a seagrass vegetated area of the Bay of Palma (Mallorca, Spain). Results showed a contrast between the planktonic compartment, which was on average near metabolic balance (-4.6 +/- 5.9 mmol O-2 m(-2) d(-1)) and the benthic compartment, which was autotrophic (17.6 +/- 8.5 mmol O-2 m(-2) d(-1)). During two cruises in March and June 2002, planktonic and benthic incubations were performed at several stations in the bay to estimate the whole-system metabolism and to examine its relationship with partial pressure of CO2 (pCO(2)) and apparent oxygen utilisation (AOU) spatial patterns. Moreover, during the second cruise, when the residence time of water was long enough, net ecosystem production (NEP) estimates based on incubations were compared, over the Posidonia oceanica meadow, to rates derived from dissolved inorganic carbon (DIC) and oxygen (O-2) mass balance budgets. These budgets provided NEP estimates in fair agreement with those derived from direct metabolic estimates based on incubated samples over the Posidonia oceanica meadow. Whereas the seagrass community was autotrophic, the excess organic carbon production therein could only balance the planktonic heterotrophy in shallow waters relative to the maximum depth of the bay ( 55 m). This generated a horizontal gradient from autotrophic or balanced communities in the shallow seagrass-covered areas, to strongly heterotrophic communities in deeper areas of the bay. It seems therefore that, on an annual scale in the whole bay, the organic matter production by the Posidonia oceanica may not be sufficient to fully compensate the heterotrophy of the planktonic compartment, which may require external organic carbon inputs, most likely from land. [less ▲]

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See detailPreliminary results on the biogeochemistry in the Mekong estuary and delta (Vietnam)
Borges, Alberto ULg; Koné; Schiettecatte, L. S. et al

Poster (2005)

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See detailNet ecosystem metabolism in a micro-tidal estuary (Randers Fjord, Denmark): evaluation of methods
Gazeau, Frédéric; Borges, Alberto ULg; Barrón, Cristina et al

in Marine Ecology. Progress Series (2005), 301

The metabolic status, the difference between organic matter production and consumption of an estuary (Randers Fjord, Denmark) has been assessed based on 2 field cruises in April and August 2001 and a ... [more ▼]

The metabolic status, the difference between organic matter production and consumption of an estuary (Randers Fjord, Denmark) has been assessed based on 2 field cruises in April and August 2001 and a number of approaches: (1) the oxygen (02) incubation method, (2) dissolved inorganic carbon (DIC) budgets, (3) the response surface difference (RSD) method based on diel O-2 changes and (4) land-ocean interaction in the coastal zone (LOICZ) budgets based on dissolved inorganic phosphorus (DIP). Although each method has its own associated limitations and uncertainties, the above approaches converged most of the time in consistent metabolic estimates, both in sign and magnitude, and revealed that this system was near metabolic balance in spring (net ecosystem production: NEP similar to 0) and net heterotrophic in summer (NEP similar to -50 mmol C m(-2) d(-1)). In this shallow estuary (mean depth = 1.6 m), the benthic compartment was very active and represented 70 and 30% of the total gross primary production in April and August, respectively. NEP rates measured during this study are in the range of previously reported rates in estuaries. [less ▲]

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See detailAlkenone carbon isotopes during a bloom of Emiliania huxleyi: Effects of CO2 concentration and production
Benthien, Albert; Riebesell, Ulf; Engel, Anja et al

Poster (2004, September 05)

The carbon isotopic composition of the C37-alkenones has been used in various paleoceanographic studies to estimate the ancient surface water CO2 concentration [CO2aq]. A number of recent culture, field ... [more ▼]

The carbon isotopic composition of the C37-alkenones has been used in various paleoceanographic studies to estimate the ancient surface water CO2 concentration [CO2aq]. A number of recent culture, field and sediment studies, however, indicate that the carbon isotopic fractionation in haptophyte algae is predominantly controlled by physiological processes and environmental factors other than the ambient [CO2aq]. The most prominent factors are algal growth rate, nutrient availability, light intensity, the carbon uptake mechanism, and the carbon source. To what extent these different factors might affect the carbon isotopic signal of alkenones ultimately preserved in the sediment is still under debate. Causes of uncertainty are the individual strenghts and weaknesses of the different methodological approaches. Culture experiments, for example, cannot perfectly recreate the sum of natural growth conditions and physical processes affecting the carbon isotopic signal in the field and its preservation in the sediment. On the other hand, core-top data represent several hundred to a couple of thousand years and therefore only reflect an average. Here, we present the first study testing the effects of [CO2aq] on the alkenone isotopic signal under natural bloom conditions in a semi-closed system. In a series of 9 floating mesocosms in a Norwegian fjord a bloom of Emiliania huxleyi was followed over a three week period. The mesocosms were covered by gas tight tents. The atmospheric and seawater pCO2 were manipulated to achieve different CO2 levels in the tent atmosphere ranging from pre-industrial (190 ppmv) to year 2100 levels (680 ppmv) as predicted by the IPCC’s report. We found that during the exponential growth phase the isotopic fractionation of alkenones decreased by 5 to 7 per mill and reached a plateau during the stationary phase. During the stationary phase the alkenone content per cell increased from 1-2 pg/cell to 6-8 pg/cell. Between the [CO2aq] treatments we observed an alkenone isotopic difference of only 2 per mill. These results indicate that changes in algal physiology and/or environmental conditions occuring during the course of an algal bloom strongly affect alkenone isotope fractionation. This effect overrides a comparatively small variation in the alkenone isotopic signal due to [CO2aq]. Implications for alkenone isotopic fractionation as a paleo-production or paleo-nutrient proxy will be discussed. [less ▲]

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See detailDelayed and reduced coccolithophorid calcification under elevated PCO2
Delille, Bruno ULg; Harlay, Jérôme ULg; Zondervan, Ingrid et al

Poster (2004, May 10)

Numerous experiments to date have demonstrated that elevated PCO2 is detrimental to biogenic calcification rates. However, most of these experiments have been realized in batch or continuous cultures and ... [more ▼]

Numerous experiments to date have demonstrated that elevated PCO2 is detrimental to biogenic calcification rates. However, most of these experiments have been realized in batch or continuous cultures and give little information on the dynamics of calcification in natural conditions. The present work describes the development and decay of a nutrient-induced bloom of the coccolithophorid Emiliania huxleyi in a mesocosm experiment. The monitoring of Dissolved Inorganic Carbon (DIC) and Total Alkalinity (TAlk) within the seawater enclosures allowed us to describe comprehensively day to day dynamics of both calcification and organic carbon production. Three atmospheric PCO2 conditions (glacial, present and next century) were simulated by bubbling CO2 mixtures, while total alkalinity was left to evolve from its present value. No conspicuous change of Net Community Production under elevated PCO2 was recorded while the production of inorganic carbon appeared to be affected in two ways. Firstly, the production rate of inorganic carbon appeared to be lowered by 40% in the next century PCO2 conditions, decreasing concomitantly the calcification to photosynthesis ratio from 0.75 (glacial conditions) to 0.45 (next century conditions). Secondly, the onset of calcification was delayed by 24~48h under elevated PCO2 conditions, reducing the overall length of calcification in the course of the bloom. These two effects would act to reduce the amount of precipitated CaCO3 by coccolithophorids in a High CO2 world [less ▲]

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See detailCrude oil bioremediation in sub-Antarctic intertidal sediments: chemistry and toxicity of oiled residues
Pelletier, Emilien; Delille, Daniel; Delille, Bruno ULg

in Marine Environmental Research (2004), 57(4), 311-327

The effectiveness of fertilizers for crude oil bioremediation in sub-Antarctic intertidal sediments was tested over a one-year period in a series of ten (10) experimental enclosures. Chemical, microbial ... [more ▼]

The effectiveness of fertilizers for crude oil bioremediation in sub-Antarctic intertidal sediments was tested over a one-year period in a series of ten (10) experimental enclosures. Chemical, microbial and toxicological parameters demonstrated the effectiveness of various fertilizers in a pristine environment where hydrocarbon degrading bacteria (HDB) had not been stimulated by previous accidental spills or human activities. The low temperature of seawater (3-4 degreesC) had no obvious effects on the HDB community and the bioremediation process. Over 90% of n-alkanes were degraded in the first six months and most light aromatics (2-3 rings) disappeared during the first year of observation. The toxicity of oiled residues (Microtox(R) SP) was significantly reduced in the first 6 months of the process, but it increased again in the last months of the experiment. One of the fertilizers containing fishbone compost enriched with urea, inorganic phosphorus and a lipidic surfactant reduced significantly the toxicity of oil residues in the last 3 months of the experiment. Interstitial waters collected below the oil slicks during the remediation showed no toxicity, and even stimulated Vibrio fischeri. When comparing all fertilizers to the control plots, a good correlation (r(2) = 0.82) was found between the growth rate of HDB and the degradation rate of n-alkanes in the first 90 days of the experiment only indicating that fertilizers were efficient for at least 3 months but their beneficial effects were lost after 6 months. (C) 2003 Elsevier Ltd. All rights reserved. [less ▲]

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See detailOn the coupling of primary production and calcification at the continental margin
Harlay, Jérôme ULg; Chou, Lei; Roevros, Nathalie et al

Poster (2004, March 05)

Until now, little attention has been paid to the processes controlling the production, dissolution and fate of biogenic calcium carbonate in the oceans. It is however well known that net deposition rates ... [more ▼]

Until now, little attention has been paid to the processes controlling the production, dissolution and fate of biogenic calcium carbonate in the oceans. It is however well known that net deposition rates of inorganic carbon to the sediments are comparable to those of organic matter. There remains still large uncertainties concerning the production and redissolution of biogenic carbonate in the marine system and thus about the role of the carbonate pump in response to anthropogenic CO2 perturbations. The understanding of these processes is also a prerequisite to predict the response of marine organisms to global environmental changes. In the framework of the Belgian global change programme, we have developed a project devoted to the study of the inorganic carbon cycle in the Bay of Biscay where coccolithophorid blooms occur frequently. The study focuses on processes associated with the oceanic production and dissolution of calcium carbonate, by combining field investigations, laboratory experiments and modelling efforts. Remote sensing demonstrates a close relationship between vertical mixing along the continental margin and the development of the phytoplankton bloom. We will present here, results of 14C incorporation experiments used to evaluate the rate of production of organic and inorganic particulate carbon, obtained during a coccolithophorid spring bloom in the investigated area. A tentative mass balance of the carbon fluxes for this area will be presented, confirming the importance that the calcium carbonate pump may play in the oceanic system. [less ▲]

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