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| Fonseca-batista, Debany; Li, Xuefeng; Riou, Virginie; Michotey, Valérie; Deman, Forian; Fripiat, François; Guasco, Sophie; Brion, Natacha; Lemaitre, Nolwenn; Tonnard, Manon; Gallinari, Morgane; Planquette, Hélène; Planchon, Frédéric; Sarthou, Géraldine; Elskens, Marc; Laroche, Julie; Chou, Lei; Dehairs, Frank. |
| Diazotrophic activity and primary production (PP) were investigated along two transects (Belgica BG2014/14 and GEOVIDE cruises) off the western Iberian Margin and the Bay of Biscay (38.8–46.5°N; 8.0–19.7°W) in May 2014 close to the end of the spring bloom. We report substantial N2 fixation activities, reaching up to 65nmolNL−1d−1 and 1533µmolNm−2d−1 close to the Iberian Margin between 38.8°N and 40.7°N. Similar figures in the basin have only been reported in the temperate and tropical western North Atlantic waters with coastal, shelf or mesohaline characteristics, as opposed to the mostly open ocean conditions studied here. In agreement with previous studies, the qualitative assessment of nifH gene diversity (encoding the nitrogenase enzyme that fixes N2)... |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00461/57266/59317.pdf |
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| Ody, Anouck; Thibaut, Thierry; Berline, Léo; Changeux, Thomas; André, Jean-michel; Chevalier, Cristèle; Blanfuné, Aurélie; Blanchot, Jean; Ruitton, Sandrine; Stiger-pouvreau, Valerie; Connan, Solène; Grelet, Jacques; Aurelle, Didier; Guéné, Mathilde; Bataille, Hubert; Bachelier, Celine; Guillemain, Dorian; Schmidt, Natascha; Fauvelle, Vincent; Guasco, Sophie; Ménard, Frédéric. |
| The present study reports on observations carried out in the Tropical North Atlantic in summer and autumn 2017, documenting Sargassum aggregations using both ship-deck observations and satellite sensor observations at three resolutions (MSI-10 m, OLCI-300 m, VIIRS-750 m and MODIS-1 km). Both datasets reported that in summer, Sargassum aggregations were mainly observed off Brazil and near the Caribbean Islands, while they accumulated near the African coast in autumn. Based on in situ observations, we propose a five-class typology allowing standardisation of the description of in situ Sargassum raft shapes and sizes. The most commonly observed Sargassum raft type was windrows, but large rafts composed of a quasi-circular patch hundreds of meters wide were... |
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| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00514/62609/66969.pdf |
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| Jacquet, Stéphanie Hm; Lefèvre, Dominique; Tamburini, Christian; Garel, Marc; Le Moigne, Frédéric Ac; Bhairy, Nagib; Guasco, Sophie. |
| n the ocean, remineralization rate associated with sinking particles is a crucial variable. Since the 1990s, particulate biogenic barium (Baxs) has been used as an indicator of carbon remineralization by applying a transfer function relating Baxs to O2 consumption (Dehairs's transfer function, Southern Ocean-based). Here, we tested its validity in the Mediterranean Sea (ANTARES/EMSO-LO) for the first time by investigating connections between Baxs, prokaryotic heterotrophic production (PHP) and oxygen consumption (JO2-Opt; optodes measurement). We show that (1) higher Baxs (409 pM; 100–500 m) occurs in situations where integrated PHP (PHP100/500=0.90) is located deeper, (2) higher Baxs occurs with increasing JO2-Opt, and (3) there is similar magnitude... |
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| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00648/76038/76959.pdf |
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| Jacquet, Stéphanie Hm; Tamburini, Christian; Garel, Marc; Dufour, Aurélie; Van Vambeke, France; Le Moigne, Frédéric Ac; Bhairy, Nagib; Guasco, Sophie. |
| We report on the sub-basins variability of particulate organic carbon (POC) remineralization in the central and western Mediterranean Sea during a late spring period (PEACETIME cruise). POC remineralization rates (MR) were estimated using the excess non-lithogenic particulate barium (Baxs) inventories in mesopelagic waters (100–1000 m) and compared with prokaryotic heterotrophic production (PHP). MR range from 25 ± 2 to 306 ± 70 mg C m−2 d−1. Results reveal larger MR processes in the Algerian (ALG) basin compared to the Tyrrhenian (TYR) and Ionian (ION) basins. Baxs inventories and PHP also indicates that significant remineralization occurs over the whole mesopelagic layers in the ALG basin in contrast to the ION and TYR basins where remineralization is... |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00652/76399/77438.pdf |
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| Garel, Marc; Bonin, Patricia; Martini, Severine; Guasco, Sophie; Roumagnac, Marie; Bhairy, Nagib; Armougom, Fabrice; Tamburini, Christian. |
| The pelagic realm of the dark ocean is characterized by high hydrostatic pressure, low temperature, high-inorganic nutrients, and low organic carbon concentrations. Measurements of metabolic activities of bathypelagic bacteria are often underestimated due to the technological limitations in recovering samples and maintaining them under in situ environmental conditions. Moreover, most of the pressure-retaining samplers, developed by a number of different labs, able to maintain seawater samples at in situ pressure during recovery have remained at the prototype stage, and therefore not available to the scientific community. In this paper, we will describe a ready-to-use pressure-retaining sampler, which can be adapted to use on a CTD-carousel sampler. As well... |
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Palavras-chave: Pressure-retaining sampler; Deep sea; In situ sampling; Prokaryotic activities; Prokaryotic diversity. |
| Ano: 2019 |
URL: https://archimer.ifremer.fr/doc/00688/79992/82967.pdf |
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| Van Wambeke, France; Pulido, Elvira; Catala, Philippe; Dinasquet, Julie; Djaoudi, Kahina; Engel, Anja; Garel, Marc; Guasco, Sophie; Barbara, Marie; Nunige, Sandra; Taillandier, Vincent; Zancker, Birthe; Tamburini, Christian. |
| Ectoenzymatic activity, prokaryotic heterotrophic abundances and production were determined in the Mediterranean Sea. Sampling was carried out in the sub-surface, the deep chlorophyll maximum layer (DCM), the core of the Levantine intermediate waters and in the deeper part of the mesopelagic layers. Michaelis–Menten kinetics were assessed using a large range of concentrations of fluorogenic substrates (0.025 to 50 µM). As a consequence, Km (Michaelis–Menten half-saturation constant) and Vm (maximum hydrolysis velocity) parameters were determined for both low- and high-affinity enzymes for alkaline phosphatase, aminopeptidase (LAP) and β-glucosidase (βGLU). Based on the constant derived from the high-LAP-affinity enzyme (0.025–1 µM substrate concentration... |
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| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00642/75452/76268.pdf |
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| Amiraux, Rémi; Burot, Christopher; Bonin, Patricia; Massé, Guillaume; Guasco, Sophie; Babin, Marcel; Vaultier, Frédéric; Rontani, Jean-françois. |
| During sea-ice melt in the Arctic, primary production by sympagic (sea-ice) algae can be exported efficiently to the seabed if sinking rates are rapid and activities of associated heterotrophic bacteria are limited. Salinity stress due to melting ice has been suggested to account for such low bacterial activity. We further tested this hypothesis by analyzing samples of sea ice and sinking particles collected from May 18 to June 29, 2016, in western Baffin Bay as part of the Green Edge project. We applied a method not previously used in polar regions—quantitative PCR coupled to the propidium monoazide DNA-binding method—to evaluate the viability of bacteria associated with sympagic and sinking algae. We also measured cis-trans isomerase activity, known to... |
| Tipo: Text |
Palavras-chave: Bacteria; Sea ice; Sympagic algae; Ice biota; Viability; Stress factors; Salinity; Bactericidal free fatty acids; Carbon export. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00681/79329/81840.pdf |
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