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| Van Wambeke, France; Pfreundt, Ulrike; Barani, Aude; Berthelot, Hugo; Moutin, Thierry; Rodier, Martine; Hess, Wolfgang R.; Bonnet, Sophie. |
| Studies investigating the fate of diazotrophs through the microbial food web are lacking, although N2 fixation can fuel up to 50 % of new production in some oligotrophic oceans. In particular, the role played by heterotrophic prokaryotes in this transfer is largely unknown. In the frame of the VAHINE (VAriability of vertical and tropHIc transfer of diazotroph derived N in the south wEst Pacific) experiment, three replicate large-volume (∼ 50 m3) mesocosms were deployed for 23 days in the new Caledonia lagoon and were intentionally fertilized on day 4 with dissolved inorganic phosphorus (DIP) to stimulate N2 fixation. We specifically examined relationships between heterotrophic bacterial production (BP) and N2 fixation or primary production, determined... |
| Tipo: Text |
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| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00342/45331/44792.pdf |
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| Zhao, Li; Denis, Michel; Barani, Aude; Beker, Beatriz; Mante, Claude; Xiao, Tian; Gregori, Gerald. |
| The composition of ultraphytoplankton (10 m) sampled in surface waters (1 m depth) was investigated during summer 2010 in the Bay of Marseille (NW Mediterranean) using flow cytometry. In addition to groups of Synechococcus, Prochlorococcus, picoeukaryotes and nanoeukaryotes, an unidentified additional cluster was observed. The particles forming this cluster had a high abundance (7 10(4) events mL(1)), with both orange and red fluorescence intensities like Synechococcus, but with a size signal larger than that of 2 m fluorospheres (beads). These unknown particles were sorted out by flow cytometry and then observed by epifluorescence microscopy: they appeared to be chain-forming microorganisms, just like trichomes of some diazotroph cyanobacteria with one... |
| Tipo: Text |
Palavras-chave: Ultraphytoplankton; Trichomes; Bay of Marseille; Flow cytometry; Cell sorting. |
| Ano: 2012 |
URL: https://archimer.ifremer.fr/doc/00372/48292/48454.pdf |
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| Djaoudi, Kahina; Van Wambeke, France; Barani, Aude; Bhairy, Nagib; Chevaillier, Servanne; Desboeufs, Karine; Nunige, Sandra; Labiadh, Mohamed; Des Tureaux, Thierry Henry; Lefevre, Dominique; Nouara, Amel; Panagiotopoulos, Christos; Tedetti, Marc; Pulido-villena, Elvira. |
| The surface ocean receives important amounts of organic carbon from atmospheric deposition. The degree of bioavailability of this source of organic carbon will determine its impact on the marine carbon cycle. In this study, the potential availability of dissolved organic carbon (DOC) leached from both desert dust and anthropogenic aerosols to marine heterotrophic bacteria was investigated. The experimental design was based on 16 d incubations, in the dark, of a marine bacterial inoculum into artificial seawater amended with water-soluble Saharan dust (D treatment) and anthropogenic (A treatment) aerosols, so that the initial DOC concentration was similar between treatments. Glucose-amended (G) and non-amended (control) treatments were run in parallel. Over... |
| Tipo: Text |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00677/78941/81326.pdf |
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| Banaru, Daniela; Carlotti, Francois; Barani, Aude; Gregori, Gerald; Neffati, Nada; Harmelin-vivien, Mireille. |
| Stable isotope ratios of six size fractions of zooplankton (80 to >2000 mm) were analyzed seasonally in 2009-2010 at the SOMLIT site in the Bay of Marseille. Isotopic ratios generally increased with zooplankton size. The highest delta N-15 values were observed in the 1000-2000 mm fraction. The largest size class (>2000 mu m), dominated by gelatinous plankton, had lower delta N-15 values due to the low isotopic signatures of most of these organisms. In the larger size fractions (>1000 mu m), isotopic ratios were measured at the taxon level. Brachyuran, stomatopod, teleost and cephalopod larvae showed the highest delta N-15 values, and salps and pteropods the lowest ones. Lower values of both delta C-13 and delta N-15 were recorded in winter and... |
| Tipo: Text |
Palavras-chave: Plankton; Delta C-13; Delta N-15; Size classes; Flow cytometry. |
| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00372/48275/48536.pdf |
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| Caffin, Mathieu; Berthelot, Hugo; Cornet-barthaux, Veronique; Barani, Aude; Bonnet, Sophie. |
| Biological dinitrogen (N2) fixation provides the major source of new nitrogen (N) to the open ocean, contributing more than atmospheric and riverine inputs to the N supply. Yet the fate of the diazotroph-derived N (DDN) in the planktonic food web is poorly understood due to technical limitations. The main goals of this study were to (i) quantify how much of DDN is released to the dissolved pool during N2 fixation and how much is transferred to bacteria, phytoplankton and zooplankton, (ii) to compare the DDN release and transfer efficiencies under contrasting N2 fixation activity and diversity the oligotrophic waters of the Western Tropical South Pacific (WTSP) Ocean. We used nanometer scale secondary ion mass spectrometry (nanoSIMS) coupled with 15N2... |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00419/53003/53951.pdf |
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