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| Registros recuperados: 12 | |
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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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| 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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| 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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| 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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| Joubert, W. R.; Thomalla, S. J.; Waldron, H. N.; Lucas, M. I.; Boye, M.; Le Moigne, F. A. C.; Planchon, F.; Speich, Sabrina. |
| As part of the Bonus-GoodHope (BGH) campaign, (15)N-labelled nitrate, ammonium and urea uptake measurements were made along the BGH transect from Cape Town to similar to 60 degrees S in late austral summer, 2008. Our results are categorised according to distinct hydrographic regions defined by oceanic fronts and open ocean zones. High regenerated nitrate uptake rate in the oligotrophic Subtropical Zone (STZ) resulted in low f-ratios (f = 0.2) with nitrogen uptake being dominated by rho urea, which contributed up to 70% of total nitrogen uptake. Size fractionated chlorophyll data showed that the greatest contribution (>50 %) of picophytoplankton (<2 mu m) were found in the STZ, consistent with a community based on regenerated production. The... |
| Tipo: Text |
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| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00054/16563/14075.pdf |
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| Laurenceau-cornec, E.c.; Trull, T.w.; Davies, D.m.; Bray, S.g.; Doran, J.; Planchon, F.; Carlotti, F.; Jouandet, M.p.; Cavagna, A.j.; Waite, A.m.; Blain, S.. |
| The first KErguelen Ocean and Plateau compared Study (KEOPS1), conducted in the naturally iron-fertilised Kerguelen bloom, demonstrated that fecal material was the main pathway for exporting carbon to the deep ocean during summer (January-February 2005), suggesting a limited role of direct export via phytodetrital aggregates. The KEOPS2 project reinvestigated this issue during the spring bloom initiation (October-November 2011), when zooplankton communities may exert limited grazing pressure, and further explored the link between carbon flux, export efficiency and dominant sinking particles depending upon surface plankton community structure. Sinking particles were collected in polyacrylamide gel-filled and standard free-drifting sediment traps (PPS3/3),... |
| Tipo: Text |
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| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00255/36641/35223.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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| 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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| Sarthou, G.; Bucciarelli, Eva; Chever, Fanny; Hansard, S. P.; Gonzalez-davila, M.; Santana-casiano, J. M.; Planchon, F.; Speich, Sabrina. |
| Labile Fe(II) distributions were investigated in the Sub-Tropical South Atlantic and the Southern Ocean during the BONUS-GoodHope cruise from 34 to 57 degrees S (February-March 2008). Concentrations ranged from below the detection limit (0.009 nM) to values as high as 0.125 nM. In the surface mixed layer, labile Fe(II) concentrations were always higher than the detection limit, with values higher than 0.060nM south of 47 degrees S, representing between 39% and 63% of dissolved Fe (DFe). Apparent biological production of Fe(II) was evidenced. At intermediate depth, local maxima were observed, with the highest values in the Sub-Tropical domain at around 200 m, and represented more than 70% of DFe. Remineralization processes were likely responsible for those... |
| Tipo: Text |
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| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00048/15918/13345.pdf |
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| Bowie, A. R.; Van Der Merwe, P.; Queroue, Fabien; Trull, Thomas; Fourquez, M.; Planchon, F.; Sarthou, Geraldine; Chever, Fanny; Townsend, A. T.; Obernosterer, I.; Sallee, Jean-baptiste; Blain, S.. |
| Iron availability in the Southern Ocean controls phytoplankton growth, community composition and the uptake of atmospheric CO2 by the biological pump. The KEOPS-2 (KErguelen Ocean and Plateau compared Study 2) "process study", took place around the Kerguelen Plateau in the Indian sector of the Southern Ocean. This is a region naturally fertilised with iron on the scale of hundreds to thousands of square kilometres, producing a mosaic of spring blooms which show distinct biological and biogeochemical responses to fertilisation. This paper presents biogeochemical iron budgets (incorporating vertical and lateral supply, internal cycling, and sinks) for three contrasting sites: an upstream high-nutrient low-chlorophyll reference, over the plateau and in the... |
| Tipo: Text |
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| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00276/38726/37233.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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| 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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| Registros recuperados: 12 | |
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