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| Registros recuperados: 12 | |
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| Fourquez, Marion; Obernosterer, Ingrid; Blain, Stephane. |
| Heterotrophic bacteria are key players in the biogeochemical cycle of iron (Fe) in the ocean, but the capability of different bacterial groups to access this micronutrient is ignored thus far. The aim of our study was to develop a protocol for the combined application of microautoradiography (MICRO) and catalyzed reporter depositionfluorescence in situ hybridization (CARD-FISH) using the radioisotope 55Fe. Among the different washing solutions tested, Ti-citrate-EDTA was the most efficient for the removal of extracellular 55Fe providing sufficiently low background values. We further demonstrate that the washing of cells with Ti-citrate-EDTA and the fixation with paraformaldehyde or formaldehyde do not induce leakage of intracellular 55Fe. Incubating... |
| Tipo: Text |
Palavras-chave: Microautoradiography; 55Fe; CARD-FISH; Marine bacteria. |
| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00143/25403/23555.pdf |
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| Guinet, Christophe; Xing, X.; Walker, E; Monestiez, P; Marchand, S.; Picard, Baptiste; Jaud, T.; Authier, Matthieu; Cotte, Cedric; Dragon, Ac; Diamond, E; Antoine, David; Lovell, P.; Blain, Stephane; D'Ortenzio, Fabrizio; Claustre, Herve. |
| In situ observation of the marine environment has traditionally relied on ship-based platforms. The obvious consequence is that physical and biogeochemical properties have been dramatically undersampled, especially in the remote Southern Ocean (SO). The difficulty in obtaining in situ data represents the major limitations to our understanding, and interpretation of the coupling between physical forcing and the biogeochemical response. Southern elephant seals (Mirounga leonina) equipped with a new generation of oceanographic sensors can measure ocean structure in regions and seasons rarely observed with traditional oceanographic platforms. Over the last few years, seals have allowed for a considerable increase in temperature and salinity profiles from the... |
| Tipo: Text |
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| Ano: 2013 |
URL: http://archimer.ifremer.fr/doc/00185/29663/28034.pdf |
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| Trull, Thomas; Davies, Diana M.; Dehairs, Frank; Cavagna, Anne-julie; Lasbleiz, Marine; Laurenceau Cornec, Emmanuel C.; D'Ovidio, Francesco; Planchon, Frederic; Leblanc, Karine; Queguiner, Bernard; Blain, Stephane. |
| We examined phytoplankton community responses to natural iron fertilisation at 32 sites over and downstream from the Kerguelen Plateau in the Southern Ocean during the austral spring bloom in October-November 2011. The community structure was estimated from chemical and isotopic measurements (particulate organic carbon - POC; C-13-POC; particulate nitrogen -PN; N-15-PN; and biogenic silica - BSi) on size-fractionated samples from surface waters (300, 210, 50, 20, 5, and 1 mu m fractions). Higher values of C-13-POC (vs. co-located C-13 values for dissolved inorganic carbon -DIC) were taken as indicative of faster growth rates and higher values of N-15-PN (vs. co-located N-15-NO3 source values) as indicative of greater nitrate use (rather than ammonium use,... |
| Tipo: Text |
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| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00255/36642/35222.pdf |
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| Debeljak, Pavla; Toulza, Eve; Beier, Sara; Blain, Stephane; Obernosterer, Ingrid. |
| Iron (Fe) is a limiting nutrient in large regions of the ocean, but the strategies of prokaryotes to cope with this micronutrient are poorly known. Using a gene‐specific approach from metatranscriptomics data, we investigated 7 Fe‐related metabolic pathways in microbial communities from High Nutrient Low Chlorophyll and naturally Fe‐fertilized waters in the Southern Ocean. We observed major differences in the contribution of prokaryotic groups at different taxonomic levels to transcripts encoding Fe uptake‐mechanisms, intracellular Fe storage and replacement, and Fe‐related pathways in the tricarboxylic acid (TCA) cycle. The composition of the prokaryotic communities contributing to the transcripts of a given Fe‐related pathway was overall independent of... |
| Tipo: Text |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00488/59921/63113.eps |
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| Mantoura, F; Coppola, Laurent; Cousin, M.; Antoine, David; Beguery, Laurent; Blain, Stephane; Bouin, Marie-noelle; Cadiou, Jean-francois; Durrieu De Madron, Xavier; Forget, Philippe; Fraunie, Philippe; Gojak, Carl; Gorsky, Gaby; Goyet, Catherine; Lebaron, Philippe; Lellouche, Jean-michel; Ludwig, Hubert; Molcard, Anne; Mortier, Laurent; Petit De La Villeon, Loic; Petrenko, Anne; Piazzola, J.; Queguiner, B.; Raimbault, Patrick; Rigaud, Vincent; Sempere, Richard; Tamburini, Jean-simon; Testor, Pierre; Vuillemin, Renaud; Zakardjian, B.. |
| Tipo: Text |
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| Ano: 2009 |
URL: http://archimer.ifremer.fr/doc/00122/23341/21166.pdf |
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| Jouandet, Marie-paule; Trull, Thomas W.; Guidi, Lionel; Picheral, Marc; Ebersbach, Friederike; Stemmann, Lars; Blain, Stephane. |
| We recorded vertical profiles of size distributions of particles (ranging from 0.052 to several mm in equivalent spherical diameter) in the natural iron-fertilized bloom southeast of Kerguelen Island (Southern Ocean) and in surrounding high-nutrient, low-chlorophyll (HNLC) waters with an Under Water Video Profiler during the Kerguelen Ocean and Plateau Compared Study cruise (Jan-Feb 2005). Total particle numerical abundance and total particle volume (TPV) in the 0-200-m layer were respectively 3-fold and 20-fold higher in the bloom, and integrated TPV was correlated to integrated chlorophyll concentration. The difference persisted well into the ocean interior with a 10-fold higher TPV at 400-m depth beneath the natural iron-fertilized bloom. Below 400 m,... |
| Tipo: Text |
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| Ano: 2011 |
URL: https://archimer.ifremer.fr/doc/00214/32507/30994.pdf |
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| Laurenceau-cornec, Emmanuel C.; Trull, Thomas W.; Davies, Diana M.; De La Rocha, Christina L.; Blain, Stephane. |
| During the second KErguelen Ocean and Plateau compared Study (KEOPS2) in October-November 2011, marine snow was formed in roller tanks by physical aggregation of phytoplankton assemblages sampled at 6 stations over and downstream of the Kerguelen Plateau. Sinking velocities, morphology, bulk composition (transparent exopolymer particles, biogenic silica, particulate organic carbon), and phytoplankton contents were measured individually on 66 aggregates to identify controls on sinking velocities. Equivalent spherical diameters (ESD) ranged from 1 to 12 mm, and the particle aspect ratios, Corey shape factors, and fractal dimensions (D-F1 = 1.5, D-F2 = 1.8) were close to those of smaller natural aggregates (0.2 to 1.5 mm) collected in polyacrylamide... |
| Tipo: Text |
Palavras-chave: Sinking velocity Marine snow; Aggregation; Phytoplankton; Porosity. |
| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00352/46275/46044.pdf |
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| Xing, Xiaogang; Claustre, Herve; Blain, Stephane; D'Ortenzio, Fabrizio; Antoine, David; Ras, Josephine; Guinet, Christophe. |
| As the proxy for Chlorophyll a (Chl a) concentration, thousands of fluorescence profiles were measured by instrumented elephant seals in the Kerguelen region (Southern Ocean). For accurate retrieval of Chl a concentrations acquired by in vivo fluorometer, a two-step procedure is applied: 1) A predeployment intercalibration with accurate determination by high performance liquid chromatography (HPLC) analysis, which not only calibrates fluorescence in appropriate Chl a concentration units, but also strongly reduces variability between fluorometers, and 2) a profile-by-profile quenching correction analysis, which effectively eliminates the fluorescence quenching issue at surface around noon, and results in consistent profiles between day and night. The... |
| Tipo: Text |
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| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00248/35965/36927.pdf |
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| Landa, Marine; Blain, Stephane; Christaki, Urania; Monchy, Sebastien; Obernosterer, Ingrid. |
| Marine microbes have a pivotal role in the marine biogeochemical cycle of carbon, because they regulate the turnover of dissolved organic matter (DOM), one of the largest carbon reservoirs on Earth. Microbial communities and DOM are both highly diverse components of the ocean system, yet the role of microbial diversity for carbon processing remains thus far poorly understood. We report here results from an exploration of a mosaic of phytoplankton blooms induced by large-scale natural iron fertilization in the Southern Ocean. We show that in this unique ecosystem where concentrations of DOM are lowest in the global ocean, a patchwork of blooms is associated with diverse and distinct bacterial communities. By using on-board continuous cultures, we identify... |
| Tipo: Text |
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| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00421/53293/54115.pdf |
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| Koedooder, Coco; Gueneugues, Audrey; Van Geersdaele, Remy; Verge, Valerie; Bouget, Francois-yves; Labreuche, Yannick; Obernosterer, Ingrid; Blain, Stephane. |
| Iron (Fe) is an essential element for marine microbial growth but is present in trace amounts (<0.1 nM) in surface waters of the ocean. In heterotrophic bacteria, Fe-limitation particularly impacts ATP production as Fe is an essential co-factor of enzymes involved in the electron-transport chain as well as the tricarboxylic acid (TCA) cycle. Fe-limitation can therefore drastically reduce both bacterial growth and respiration, consequently affecting the efficiency of organic carbon remineralization. Heterotrophic bacteria possess various strategies to cope with Fe-limitation. In the present study we tested the hypothesis that the induction of the glyoxylate shunt can represent one such strategy. Genetic approaches were used to gain insight into the... |
| Tipo: Text |
Palavras-chave: Iron; Fe-limitation; Photobacterium angustum S14; Glyoxylate shunt; Isocitrate lyase. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00468/58017/60413.pdf |
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| Closset, Ivia; Cardinal, Damien; Rembauville, Mathieu; Thil, Francois; Blain, Stephane. |
| A massive diatom-bloom is observed annually in the surface waters of the naturally Fe-fertilized Kerguelen Plateau (Southern Ocean). In this study, silicon isotopic signatures (δ30Si) of silicic acid (DSi) and suspended biogenic silica (BSi) were investigated in the whole water column with an unprecedented spatial resolution in this region, during the KEOPS-2 experiment (spring 2011). We use δ30Si measurements to track the silicon sources that fuel the bloom, and investigate the seasonal evolution of Si biogeochemical cycle in the iron fertilized area. We compare the results from a HNLC reference station with stations characterized by different degrees of iron enrichment and bloom conditions. Dissolved and particulate δ30Si signatures were generally highly... |
| Tipo: Text |
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| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00344/45528/45085.pdf |
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| Registros recuperados: 12 | |
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