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| Registros recuperados: 18 | |
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| Cavagna, A. J.; Fripiat, F.; Elskens, M.; Dehairs, F.; Mangion, P.; Chirurgien, L.; Closset, I.; Lasbleiz, M.; Flores–leiva, L.; Cardinal, D.; Leblanc, K.; Fernandez, C.; Lefèvre, D.; Oriol, L.; Blain, S.; Quéguiner, B.. |
| Although the Southern Ocean is considered a High Nutrient Low Chlorophyll area (HNLC), massive and recurrent blooms are observed over and downstream the Kerguelen Plateau. This mosaic of blooms is triggered by a higher iron supply resulting from the interaction between the Antarctic Circumpolar Current and the local bathymetry. Net primary production, N-uptake (NO3− and NH4+), and nitrification rates were measured at 8 stations in austral spring 2011 (October–November) during the KEOPS2 cruise in the Kerguelen area. Iron fertilization stimulates primary production, with integrated net primary production and growth rates much higher in the fertilized areas (up to 315 mmol C m−2 d−1 and up to 0.31 d−1, respectively) compared to the HNLC reference site (12... |
| Tipo: Text |
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| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00294/40558/39445.pdf |
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| Planchon, F.; Ballas, Dionysios; Cavagna, A. -j.; Bowie, A. R.; Davies, D.; Trull, Thomas; Laurenceau-cornec, E. C.; Van Der Merwe, P.; Dehairs, F.. |
| This study examined upper-ocean particulate organic carbon (POC) export using the Th-234 approach as part of the second KErguelen Ocean and Plateau compared Study expedition (KEOPS2). Our aim was to characterize the spatial and the temporal variability of POC export during austral spring (October-November 2011) in the Fe-fertilized area of the Kerguelen Plateau region. POC export fluxes were estimated at high productivity sites over and downstream of the plateau and compared to a high-nutrient low-chlorophyll (HNLC) area upstream of the plateau in order to assess the impact of iron-induced productivity on the vertical export of carbon. Deficits in Th-234 activities were observed at all stations in surface waters, indicating early scavenging by particles in... |
| Tipo: Text |
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| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00274/38481/36940.pdf |
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| Hoppema, M.; Dehairs, F.; Navez, J.; Monnin, C.; Jeandel, C.; Fahrbach, E.; De Baar, H. J. W.. |
| The Southern Ocean data base of dissolved barium (Bad) has been augmented with two densely sampled sections across the Weddell Gyre sampled by the icebreaker FS Polarstern during February and March 2005. Bad was found to be relatively high in the surface layer as compared to the adjacent waters north (Antarctic Circumpolar Current) and east (Antarctic Zone of the Indian sector). Compared to the inflowing water into the Weddell Gyre and also to the surface water, the deep water is characterized by a significant Ba-d enrichment. Depletion of Bad in the surface layer is associated with well-known biogeochemical processes, but we speculate that also sea-ice formation leads to the extraction of Ba from solution via barite (BaSO4) precipitation. The particulate... |
| Tipo: Text |
Palavras-chave: Barium Silicate Geochemical cycle Southern Ocean; Weddell Sea. |
| Ano: 2010 |
URL: https://archimer.ifremer.fr/doc/00460/57178/59134.pdf |
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| Jacquet, Shm; Dehairs, F.; Lefevre, D.; Cavagna, A. J.; Planchon, F.; Christaki, U.; Monin, L.; Andre, L.; Closset, I.; Cardinal, D.. |
| We report on the zonal variability of mesopelagic particulate organic carbon remineralization and deep carbon transfer potential during the Kerguelen Ocean and Plateau compared Study 2 expedition (KEOPS 2; October-November 2011) in an area of the polar front supporting recurrent massive blooms from natural Fe fertilization. Mesopelagic carbon remineralization (MR) was assessed using the excess, non-lithogenic particulate barium (Ba-xs) inventories in mesopelagic waters and compared with bacterial production (BP), surface primary production (PP) and export production (EP). Results for this early season study are compared with the results obtained during a previous study (2005; KEOPS 1) for the same area at a later stage of the phytoplankton bloom. Our... |
| Tipo: Text |
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| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00260/37140/35670.pdf |
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| Poulain, C.; Lorrain, Anne; Mas, R.; Gillikin, D. P.; Dehairs, F.; Robert, Rene; Paulet, Yves-marie. |
| The influences of diet and seawater dissolved inorganic carbon (DIC) on the carbon isotope composition of shell aragonite (Cinched in the Manila clam Ruditapes philippinarum reared under laboratory conditions were investigated. Clams were exposed to two successive negative carbon isotope shifts: a first shift in diet (delta C-13(phytoplankton)) and a second shift, 35 days later, in DIC (delta C-13(DIC)). Both successive shifts induced a decrease in delta C-13(shell). These results are the first to experimentally confirm an incorporation of respired carbon derived from food and carbon from DIC into shell carbonate of adult bivalves. Skeletal delta C-13 responded to changes in the delta C-13 of both diet and DIC in less than 7 days. Consequently, proxies... |
| Tipo: Text |
Palavras-chave: Delta C-13(shell); DIC; Salinity; Metabolic carbon; Ruditapes philippinarum; Estuarine water; Proxy. |
| Ano: 2010 |
URL: http://archimer.ifremer.fr/doc/00003/11443/8001.pdf |
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| Konn, Cecile; Charlou, Jean-luc; Donval, Jean-pierre; Holm, N. G.; Dehairs, F.; Bouillon, S.. |
| The first building blocks of life could be produced in ultramafic-hosted hydrothermal systems considering the large amounts of hydrogen and methane generated by serpentinisation and Fischer-Tropsch-Type synthesis, respectively, in those systems. The purpose of this study was to detect and characterise organic molecules in hydrothermal fluids from ultramafic-hosted hydrothermal systems in the Mid-Atlantic Ridge (MAR) region. During the EXOMAR cruise 2005, fluids from the Rainbow (36°14'N) and the Lost City (30°N) hydrothermal fields were collected and treated by Stir Bar Sorptive Extraction (SBSE) and Solid Phase Extraction (SPE). The extracts were analysed by Thermal Desorption-Gas Chromatography-Mass Spectrometry (TD-GC-MS) and GC-MS, respectively.... |
| Tipo: Text |
Palavras-chave: Serpentinisation; Organic; Ultramafic; Hydrothermal; Origin of life. |
| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/00067/17828/15576.pdf |
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| Riou, V.; Halary, S.; Duperron, S.; Bouillon, S.; Elskens, M.; Bettencourt, R.; Santos, R. S.; Dehairs, F.; Colaco, A.. |
| High densities of mussels of the genus Bathymodiolus are present at hydrothermal vents of the Mid-Atlantic Ridge. It was previously proposed that the chemistry at vent sites would affect their sulphide- and methane-oxidizing endosymbionts' abundance. In this study, we confirmed the latter assumption using fluorescence in situ hybridization on Bathymodiolus azoricus specimens maintained in a controlled laboratory environment at atmospheric pressure with one, both or none of the chemical substrates. A high level of symbiosis plasticity was observed, methane-oxidizers occupying between 4 and 39% of total bacterial area and both symbionts developing according to the presence or absence of their substrates. Using (HCO3-)-C-13 in the presence of sulphide, or... |
| Tipo: Text |
Palavras-chave: Mid-atlantic ridge; Hydrocarbon-seep mussel; Deep-sea mussels; Hydrothermal-vent; Puteoserpentis bivalvia; Mytilidae; Methane; Endosymbionts; Bacteria; Metabolism. |
| Ano: 2008 |
URL: https://archimer.ifremer.fr/doc/00207/31865/30271.pdf |
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| Planchon, F.; Cavagna, A-j.; Cardinal, Damien; Andre, L.; Dehairs, F.. |
| As part of the GEOTRACES Bonus-GoodHope (BGH) expedition (January-March 2008) in the Atlantic sector of the Southern Ocean, particulate organic carbon (POC) export was examined from the surface to the mesopelagic twilight zone using water column distributions of total Th-234 and biogenic particulate Ba (Ba-xs). Surface POC export production was estimated from steady state and non steady state modelling of Th-234 fluxes, which were converted into POC fluxes, using the POC/Th-234 ratio of large, potentially sinking particles (>53 mu m) collected via in situ pumps. Deficits in Th-234 activities were observed at all stations from the surface to the bottom of the mixed layer, yielding Th-234 export fluxes from the upper 100 m of 496 +/- 214 dpm m(-2) d(-1)... |
| Tipo: Text |
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| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00181/29206/27580.pdf |
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| Jacquet, S.h.m.; Savoye, N.; Dehairs, F.; Strass, V. H.; Cardinal, D.. |
| [1] The impact of iron fertilization on mesopelagic carbon (C) remineralization was assessed during the European Iron Fertilization Experiment (EIFEX) in the Southern Ocean by following the temporal change of excess particulate barium (also called biogenic or Ba(xs)) in the mesopelagic waters of a mesoscale eddy. Before the iron infusion the site was already sustaining a significant vertical flux of particles leading to organic remineralization in the mesopelagic. Approximately 35 d after the fertilization, mesopelagic Baxs contents provided evidence of changes in surface particulate export and of enhanced and particularly fast remineralization extending down to 1000 m. At the end of the experiment (day 36) both export and remineralization decreased.... |
| Tipo: Text |
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| Ano: 2008 |
URL: https://archimer.ifremer.fr/doc/00237/34870/33193.pdf |
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| Dehairs, F.; Fripiat, F.; Cavagna, A. -j.; Trull, T.w.; Fernandez, C.; Davies, D.; Roukaerts, A.; Fonseca Batista, D.; Planchon, F.; Elskens, M.. |
| This paper presents whole water column data for nitrate N, O isotopic composition for the Kerguelen Plateau area and the basin extending east of Heard Island, aiming at understanding the N-cycling in this naturally iron fertilized area that is characterized by large re-current phytoplankton blooms. The KEOPS 2 expedition (October-November 2011) took place in spring season and complements knowledge gathered during an earlier summer expedition to the same area (KEOPS 1, February-March 2005). As noted by others a remarkable condition of the system is the moderate consumption of nitrate over the season (nitrate remains >20 mu M) while silicic acid becomes depleted, suggesting significant recycling of nitrogen. Nitrate isotopic signatures in the upper water... |
| Tipo: Text |
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| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00260/37085/35584.pdf |
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| Fripiat, F.; Cavagna, A. -j.; Dehairs, F.; De Brauwere, A.; Andre, L.; Cardinal, D.. |
| Southern Ocean biogeochemical processes have an impact on global marine primary production and global elemental cycling, e.g. by likely controlling glacial-interglacial pCO(2) variation. In this context, the natural silicon isotopic composition (delta Si-30) of sedimentary biogenic silica has been used to reconstruct past Si-consumption:supply ratios in the surface waters. We present a new dataset in the Southern Ocean from a IPY-GEOTRACES transect (Bonus-GoodHope) which includes for the first time summer delta Si-30 signatures of suspended biogenic silica (i) for the whole water column at three stations and (ii) in the mixed layer at seven stations from the subtropical zone up to the Weddell Gyre. In general, the isotopic composition of biogenic opal... |
| Tipo: Text |
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| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00226/33769/32565.pdf |
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| Cavagna, A. J.; Fripiat, F.; Elskens, M.; Mangion, P.; Chirurgien, L.; Closset, I.; Lasbleiz, M.; Florez-leiva, L.; Cardinal, D.; Leblanc, K.; Fernandez, C.; Lefevre, D.; Oriol, L.; Blain, S.; Queguiner, B.; Dehairs, F.. |
| Although the Southern Ocean is considered a high-nutrient, low-chlorophyll (HNLC) area, massive and recurrent blooms are observed over and downstream of the Kerguelen Plateau. This mosaic of blooms is triggered by a higher iron supply resulting from the interaction between the Antarctic Circumpolar Current and the local bathymetry. Net primary production, N uptake (NO3− and NH4+), and nitrification rates were measured at eight stations in austral spring 2011 (October–November) during the KEOPS 2 cruise in the Kerguelen Plateau area. Natural iron fertilization stimulated primary production, with mixed layer integrated net primary production and growth rates much higher in the fertilized areas (up to 315 mmol C m−2 d−1 and up to 0.31 d−1 respectively)... |
| Tipo: Text |
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| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00294/40561/39448.pdf |
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| Fripiat, F.; Elskens, M.; Trull, T. W.; Blain, S.; Cavagna, A. -j.; Fernandez, C.; Fonseca-batista, D.; Planchon, F.; Raimbault, P.; Roukaerts, A.; Dehairs, F.. |
| Nitrification, the microbially mediated oxidation of ammonium into nitrate, is generally expected to be low in the Southern Ocean mixed layer. This paradigm assumes that nitrate is mainly provided through vertical mixing and assimilated during the vegetative season, supporting the concept that nitrate uptake is equivalent to the new primary production (i.e., primary production which is potentially available for export). Here we show that nitrification is significant (~40–80% of the seasonal nitrate uptake) in the naturally iron-fertilized bloom over the southeast Kerguelen Plateau. Hence, a large fraction of the nitrate-based primary production is regenerated, instead of being exported. It appears that nitrate assimilation (light dependent) and... |
| Tipo: Text |
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| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00296/40704/39700.pdf |
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| Fripiat, F.; Cavagna, A. -j.; Dehairs, F.; Speich, Sabrina; Andre, L.; Cardinal, D.. |
| Silicon isotopic signatures (delta(30)Si) of water column silicic acid (Si(OH)(4)) were measured in the Southern Ocean, along a meridional transect from South Africa (Subtropical Zone) down to 57 degrees S (northern Weddell Gyre). This provides the first reported data of a summer transect across the whole Antarctic Circumpolar Current (ACC). delta(30)Si variations are large in the upper 1000 m, reflecting the effect of the silica pump superimposed upon meridional water transfer across the ACC: the transport of Antarctic surface waters northward by a net Ekman drift and their convergence and mixing with warmer upper-ocean Si-depleted waters to the north. Using Si isotopic signatures, we determine different mixing interfaces: the Antarctic Surface Water... |
| Tipo: Text |
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| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00052/16298/13811.pdf |
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| Van Der Merwe, P.; Bowie, A. R.; Queroue, F.; Armand, L.; Blain, S.; Chever, Fanny; Davies, D.; Dehairs, F.; Planchon, F.; Sarthou, G.; Townsend, A. T.; Trull, T. W.. |
| The KEOPS2 project aims to elucidate the role of natural Fe fertilisation on biogeochemical cycles and ecosystem functioning, including quantifying the sources and processes by which iron is delivered in the vicinity of the Kerguelen Archipelago, Southern Ocean. The KEOPS2 process study used an upstream high-nutrient, low-chlorophyll (HNLC), deep water (2500 m), reference station to compare with a shallow (500 m), strongly fertilised plateau station and continued the observations to a downstream, bathymetrically trapped recirculation of the Polar Front where eddies commonly form and persist for hundreds of kilometres into the Southern Ocean. Over the Kerguelen Plateau, mean particulate (1-53 mu m) Fe and Al concentrations (pFe = 13.4 nM, pAl = 25.2 nM)... |
| Tipo: Text |
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| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00256/36676/35276.pdf |
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| Riou, V.; Bouillon, S.; Serrao Santos, R.; Dehairs, F.; Colaco, A.. |
| Bathymodiolus azoricus mussels thrive at Mid-Atlantic Ridge hydrothermal vents, where part of their energy requirements are met via an endosymbiotic association with chemolithotrophic and methanotrophic bacteria. In an effort to describe phenotypic characteristics of the two bacterial endosymbionts and to assess their ability to assimilate CO2, CH4 and multi-carbon compounds, we performed experiments in aquaria using C-13-labeled NaHCO3 (in the presence of H2S), CH4 or amino-acids and traced the incorporation of C-13 into total and phospholipid fatty acids (tFA and PLFA, respectively). 14:0; 15:0; 16:0; 16:1(n - 7) c+t; 18:1(n - 13) c+t and (n - 7) c+t; 20:1(n - 7); 20:2(n - 9,15); 18:3(n - 7) and (n - 5,10,13) PLFA were labeled in the presence of... |
| Tipo: Text |
Palavras-chave: Mid atlantic ridge; Mussel bathymodiolus azoricus; Methanotrophic bacteria; Marine invertebrates; Diversity; Organic compounds; Lipid composition; Dual symbiosis; Methane; Biomarkers. |
| Ano: 2010 |
URL: https://archimer.ifremer.fr/doc/00207/31868/30275.pdf |
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| Cavagna, A. -j.; Dehairs, F.; Bouillon, S.; Woule-ebongue, V.; Planchon, F.; Delille, B.; Bouloubassi, I.. |
| The combination of concentrations and delta C-13 signatures of Particulate Organic Carbon (POC) and sterols provides a powerful approach to study ecological and environmental changes in both the modern and ancient ocean. We applied this tool to study the biogeochemical changes in the modern ocean water column during the BONUS-GoodHope survey (February-March 2008) from Cape Basin to the northern part of the Weddell Gyre. Cholesterol and brassicasterol were chosen as ideal biomarkers of the heterotrophic and autotrophic carbon pools, respectively, because of their ubiquitous and relatively refractory nature. We document depth distributions of concentrations (relative to bulk POC) and delta C-13 signatures of cholesterol and brassicasterol combined with CO2... |
| Tipo: Text |
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| Ano: 2013 |
URL: https://archimer.ifremer.fr/doc/00265/37576/36778.pdf |
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| Cavagna, A.-j.; Dehairs, F.; Woule-ebongué, V.; Bouillon, S.; Planchon, F.; Delille, B.; Bouloubassi, I.. |
| The combination of concentrations and δ13C signatures of Particulate Organic Carbon (POC) and sterols provides a powerful approach to study ecological and environmental changes both in the modern and ancient ocean, but its application has so far been restricted to the surface area. We applied this tool to study the biogeochemical changes in the modern ocean water column during the BONUS-GoodHope survey (Feb–Mar 2008) from Cape Basin to the northern part of the Weddell Gyre. Cholesterol and brassicasterol were chosen as ideal biomarkers of the heterotrophic and autotrophic carbon pools, respectively, because of their ubiquitous and relatively refractory nature. We document depth distributions of concentrations (relative to bulk POC) and δ13C signatures of... |
| Tipo: Text |
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| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00273/38458/36853.pdf |
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| Registros recuperados: 18 | |
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