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| Gazeau, Frédéric; Ridame, Céline; Van Wambeke, France; Alliouane, Samir; Stolpe, Christian; Irisson, Jean-olivier; Marro, Sophie; Grisoni, Jean-michel; De Liège, Guillaume; Nunige, Sandra; Djaoudi, Kahina; Pulido-villena, Elvira; Dinasquet, Julie; Obernosterer, Ingrid; Catala, Philippe; Guieu, Cécile. |
| In Low Nutrient Low Chlorophyll areas, such as the Mediterranean Sea, atmospheric fluxes represent a considerable external source of nutrients likely supporting primary production especially during stratification periods. These areas are expected to expand in the future due to lower nutrient supply from sub-surface waters caused by enhanced stratification, likely further increasing the role of atmospheric deposition as a source of new nutrients to surface waters. Yet, whether plankton communities will react differently to dust deposition in a warmer and acidified environment remains an open question. The impact of dust deposition both in present and future climate conditions was assessed through three perturbation experiments in the open Mediterranean Sea.... |
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| Ano: 2021 |
URL: https://archimer.ifremer.fr/doc/00688/80015/82994.pdf |
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| Fumenia, Alain; Petrenko, Anne; Loisel, Hubert; Djaoudi, Kahina; De Verneil, Alain; Moutin, Thierry. |
| Using biogeochemical-Argo float measurements, we propose, for the first time, an optical proxy for particulate organic nitrogen concentration (PON) in the Western Tropical South Pacific, an area influenced by dinitrogen (N2) fixation. Our results show a significant relationship between the backscattering coefficient at 700 nm (bbp) and PON, especially when the latter is measured using the wet oxidation method (R2=0.87). bbp may be used to estimate PON concentrations (PONopt) between 0.02 and 0.95 ìM, allowing for unprecedented monitoring using autonomous profiling floats. The bbp vs PON relationship can be used to study phytoplanktonic biomass dynamics at relevant seasonal temporal scales, with clear evidence of PONopt as a proxy of phytoplanktonic... |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00640/75226/75367.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... |
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| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00677/78941/81326.pdf |
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| Djaoudi, Kahina; Van Wambeke, France; Coppola, Laurent; D'Ortenzio, Fabrizio; Helias-nunige, Sandra; Raimbault, Patrick; Taillandier, Vincent; Testor, Pierre; Wagener, Thibaut; Pulido-villena, Elvira. |
| An accurate understanding of the biogeochemistry of dissolved phosphate pool in the upper waters of P-depleted oceanic regions is constrained by the low sensitivity of routine phosphate measurements. In this study, by using the sensitive Liquid Waveguide Capillary Cell method, we report the first extensive cross-basin survey of nanomolar dissolved inorganic phosphate (DIP) and dissolved organic phosphate (DOP) concentration in P-depleted surface waters of the Mediterranean Sea during the stratification period. In the north western Mediterranean Sea (NWMS), DIP above the mixed layer depth (MLD) ranged between 4.9 and 26.5 nM. Along an E-W transect crossing Ionian and Tyrrhenian Seas (E-W transect), DIP above the MLD was lower, ranging between 0.9 and 11.4... |
| Tipo: Text |
Palavras-chave: The Mediterranean Sea; Dissolved inorganic phosphate; Dissolved organic phosphate; N:P ratios; Liquid waveguide capillary cell. |
| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00450/56184/57731.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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