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| Registros recuperados: 19 | |
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| Benavides, Mar; Shoemaker, Katyanne M.; Moisander, Pia H.; Niggemann, Jutta; Dittmar, Thorsten; Duhamel, Solange; Grosso, Olivier; Pujo-pay, Mireille; Hélias-nunige, Sandra; Bonnet, Sophie. |
| The western tropical South Pacific (WTSP) Ocean has been recognized as a global hotspot of dinitrogen (N2) fixation. Here, as in other marine environments across the oceans, N2 fixation studies have focused in the sunlit layer. However, studies have confirmed the importance of aphotic N2 fixation activity, although until now only one had been performed in the WTSP. In order to increase our knowledge of aphotic N2 fixation in the WTSP, here we measure N2 fixation rates and identify diazotrophic phylotypes in the mesopelagic layer along a transect spanning from New Caledonia to French Polynesia. Because non-cyanobacterial diazotrophs presumably need external dissolved organic matter (DOM) sources for their nutrition, we also identified DOM compounds using... |
| Tipo: Text |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00420/53118/54070.pdf |
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| Bonnet, Sophie; Guieu, Cecile. |
| A 1-year survey of simultaneous measurements of total atmospheric deposition and dissolved iron concentrations in surface waters (0-40 m) was performed in the northwestern Mediterranean Sea, an area with a marked seasonal hydrological regime. The total atmospheric iron flux was 1118 mg m(-2) (i.e., 20.4 mmol m(-2)). By using aluminium as a crustal marker the deposition was mainly attributed to Saharan dust deposition. Dissolved iron flux was estimated to be 42 mmol m(-2) yr(-1), of which 44% was anthropogenic in origin and 56% was of Saharan origin. Dissolved iron profiles revealed four typical situations throughout the year: (1) a winter situation with homogenous dissolved iron concentrations ranging from 0.8 to 0.9 nmol L(-1), (2) a spring situation with... |
| Tipo: Text |
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| Ano: 2006 |
URL: https://archimer.ifremer.fr/doc/00240/35098/33593.pdf |
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| Benavides, Mar; Houlbreque, Fanny; Camps, Mercedes; Lorrain, Anne; Grosso, Olivier; Bonnet, Sophie. |
| Corals aremixotrophs: they are able to fix inorganic carbon through the activity of their symbiotic dinoflagellates and to gain nitrogen from predation on plankton and uptake of dissolved organic and inorganic nutrients. They also live in close association with diverse diazotrophic communities, inhabiting their skeleton, tissue and mucus layer, which are able to fix dinitrogen (N-2). The quantity of fixed N-2 transferred to the corals and its distribution within coral compartments as well as the quantity of nitrogen assimilated through the ingestion of planktonic diazotrophs are still unknown. Here, we quantified nitrogen assimilation via (i) N-2 fixation by symbiont diazotrophs, (ii) ingestion of cultured unicellular diazotrophs and (iii) ingestion of... |
| Tipo: Text |
Palavras-chave: Scleractinian corals; Heterotrophic nutrition; Cyanothece; N-2 fixation; New Caledonia. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00356/46678/72967.pdf |
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| Stenegren, Marcus; Caputo, Andrea; Berg, Carlo; Bonnet, Sophie; Foster, Rachel A.. |
| The abundance and distribution of cyanobacterial diazotrophs were quantified in two regions (Melanesian archipelago, MA and subtropical gyre, SG) of the Western Tropical South Pacific using nifH qPCR assays. UCYN-A1 and A2 host populations were quantified using 18S rRNA qPCR assays including one newly developed assay. All phylotypes were detected in the upper photic zone (0–50 m), with higher abundances in the MA region. Trichodesmium and UCYN-B dominated, composing 81–100 % of nifH copies detected. Het-1 was the next most abundant, and co-occurred with het-2 and het-3. The two UCYN-A lineages were least abundant (<1.0–1.5 % of total nifH copies) and poorly detected (> 47 %). Abundance of the UCYN-A hosts mirrored their respective symbionts; UCYN-A1... |
| Tipo: Text |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00420/53126/54083.pdf |
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| Knapp, Angela N.; Mccabe, Kelly M.; Grosso, Olivier; Leblond, Nathalie; Moutin, Thierry; Bonnet, Sophie. |
| Constraining the rates and spatial distribution of di-nitrogen (N2) fixation fluxes to the ocean informs our understanding of the environmental sensitivities of N2 fixation as well as the timescale over which the fluxes of nitrogen (N) to and from the ocean may respond to each other. Here we quantify rates of N2 fixation as well as its contribution to export production along a zonal transect in the Western Tropical South Pacific (WTSP) Ocean using N isotope (δ15N) budgets. Comparing measurements of water column nitrate + nitrite δ15N with the δ15N of sinking particulate N at a western, central, and eastern station, these δ15N budgets indicate high, modest, and low rates of N2 fixation at the respective stations. The results also imply that N2 fixation... |
| Tipo: Text |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00420/53117/54069.pdf |
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| Bonnet, Sophie; Berthelot, Hugo; Turk-kubo, Kendra; Fawcett, Sarah; Rahav, Eyal; L'Helguen, Stephane; Berman-frank, Ilana. |
| N2 fixation rates were measured daily in large (∼ 50 m3) mesocosms deployed in the tropical southwest Pacific coastal ocean (New Caledonia) to investigate the temporal variability in N2 fixation rates in relation with environmental parameters and study the fate of diazotroph-derived nitrogen (DDN) in a low-nutrient, low-chlorophyll ecosystem. The mesocosms were fertilized with ∼ 0.8 µM dissolved inorganic phosphorus (DIP) to stimulate diazotrophy. Bulk N2 fixation rates were replicable between the three mesocosms, averaged 18.5 ± 1.1 nmol N L−1 d−1 over the 23 days, and increased by a factor of 2 during the second half of the experiment (days 15 to 23) to reach 27.3 ± 1.0 nmol N L−1 d−1. These later rates measured after the DIP fertilization are higher... |
| Tipo: Text |
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| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00333/44459/44136.pdf |
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| Fumenia, Alain; Moutin, Thierry; Bonnet, Sophie; Benavides, Mar; Petrenko, Anne; Helias Nunige, Sandra; Maes, Christophe. |
| As part of the Oligotrophy to UlTra-oligotrophy PACific Experiment cruise, which took place in the Western Tropical South Pacific during the austral summer (March–April 2015), we present data on nitrate, phosphate and on particulate and dissolved organic matter. The stoichiometric nitrogen-to-phosphorus ratios of the inorganic and organic material and the tracer N* are described. N* allows to trace changes in the proportion of fixed nitrogen due to diazotrophy and/or denitrification. Our results showed that the Melanesian archipelago waters between 160° E and 170° W are characterized by a deficit of nitrate and phosphate in the productive layer, significant dinitrogen fixation rates and an excess of particulate organic nitrogen compared to the canonical... |
| Tipo: Text |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00422/53383/54232.pdf |
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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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| Bonnet, Sophie; Caffin, Mathieu; Berthelot, Hugo; Grosso, Olivier; Benavides, Mar; Helias-nunige, Sandra; Guieu, Cecile; Stenegren, Marcus; Foster, Rachel Ann. |
| Here we report N2 fixation rates from a ∼ 4000km transect in the western and central tropical South Pacific, a particularly undersampled region in the world ocean. Water samples were collected in the euphotic layer along a west to east transect from 160°E to 160°W that covered contrasting trophic regimes, from oligotrophy in the Melanesian archipelago (MA) waters to ultra-oligotrophy in the South Pacific Gyre (GY) waters. N2 fixation was detected at all 17 sampled stations with an average depth-integrated rate of 631±286µmol N m−2 d−1 (range 196–1153µmol N m−2 d−1) in MA waters and of 85±79µmol N m−2 d−1 (range 18–172µmol N m−2 d−1) in GY waters. Two cyanobacteria, the larger colonial filamentous Trichodesmium and the smaller UCYN-B, dominated the... |
| Tipo: Text |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00419/53049/53987.pdf |
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| Bonnet, Sophie; Moutin, Thierry; Rodier, Martine; Grisoni, Jean-michel; Louis, Francis; Folcher, Eric; Bourgeois, Bertrand; Bore, Jean-michel; Renaud, Armelle. |
| On the global scale, N-2 fixation provides the major external source of reactive nitrogen to the surface ocean, surpassing atmospheric and riverine inputs, and sustains similar to 50 % of new primary production in oligotrophic environments. The main goal of the VAriability of vertical and tropHlc transfer of diazotroph derived N in the south wEst Pacific (VAHINE) project was to study the fate of nitrogen newly fixed by diazotrophs (or diazotroph-derived nitrogen) in oceanic food webs, and how it impacts heterotrophic bacteria, phytoplankton and zooplankton dynamics, stocks and fluxes of biogenic elements and particle export. Three large volume (similar to 50 m(3)) mesocosms were deployed in a tropical oligotrophic ecosystem (the New Caledonia lagoon,... |
| Tipo: Text |
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| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00344/45480/45020.pdf |
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| Guieu, Cecile; Bonnet, Sophie; Petrenko, Anne; Menkes, Christophe; Chavagnac, Valerie; Desboeufs, Karine; Maes, Christophe; Moutin, Thierry. |
| In the Western Tropical South Pacific, patches of high chlorophyll concentrations linked to the occurrence of N2-fixing organisms are found in the vicinity of volcanic islands. The survival of these organisms relies on a high bioavailable iron supply whose origin and fluxes remain unknown. Here, we measured high dissolved iron (DFe) concentrations (up to 66 nM) in the euphotic layer, extending zonally over 10 degrees longitude (174 E−175 W) at ∼20°S latitude. DFe atmospheric fluxes were at the lower end of reported values of the remote ocean and could not explain the high DFe concentrations measured in the water column in the vicinity of Tonga. We argue that the high DFe concentrations may be sustained by a submarine source, also characterized by... |
| Tipo: Text |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00444/55564/57174.pdf |
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| Dutheil, Cyril; Aumont, Olivier; Gorgues, Thomas; Lorrain, Anne; Bonnet, Sophie; Rodier, Martine; Dupouy, Cecile; Shiozaki, Takuhei; Menkes, Christophe. |
| Dinitrogen fixation is now recognized as one of the major sources of bio-available nitrogen in the ocean. Thus, N2 fixation sustains a significant part of the global primary production by supplying the most common limiting nutrient for phytoplankton growth. The Oligotrophy to UlTra-oligotrophy PACific Experiment (OUTPACE) improved the data coverage of the western tropical South Pacific, an area recently recognized as a hotspot of N2 fixation. This new development leads us to develop and test an explicit N2 fixation formulation based on the Trichodesmium physiology (the most studied nitrogen fixer) within a 3-D coupled dynamical–biogeochemical model (ROMS-PISCES). We performed a climatological numerical simulation that is able to reproduce the main physical... |
| Tipo: Text |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00419/53042/53979.pdf |
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| Caffin, Mathieu; Moutin, Thierry; Foster, Rachel Ann; Bouruet-aubertot, Pascale; Doglioli, Andrea Michelangelo; Berthelot, Hugo; Guieu, Cecile; Grosso, Olivier; Helias-nunige, Sandra; Leblond, Nathalie; Gimenez, Audrey; Petrenko, Anne Alexandra; De Verneil, Alain; Bonnet, Sophie. |
| We performed nitrogen (N) budgets in the photic layer of three contrasting stations representing different trophic conditions in the western tropical South Pacific (WTSP) Ocean during austral summer conditions (February–March 2015). Using a Lagrangian strategy, we sampled the same water mass for the entire duration of each long-duration (5 days) station, allowing us to consider only vertical exchanges for the budgets. We quantified all major vertical N fluxes both entering (N2 fixation, nitrate turbulent diffusion, atmospheric deposition) and leaving the photic layer (particulate N export). The three stations were characterized by a strong nitracline and contrasted deep chlorophyll maximum depths, which were lower in the oligotrophic Melanesian archipelago... |
| Tipo: Text |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00439/55074/56503.pdf |
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| Moutin, Thierry; Doglioli, Andrea Michelangelo; De Verneil, Alain; Bonnet, Sophie. |
| The overall goal of OUTPACE (Oligotrophy to UlTra-oligotrophy PACific Experiment) was to obtain a successful representation of the interactions between planktonic organisms and the cycle of biogenic elements in the western tropical South Pacific Ocean across trophic and N2 fixation gradients. Within the context of climate change, it is necessary to better quantify the ability of the oligotrophic ocean to sequester carbon through biological processes. OUTPACE was organized around three main objectives, which were (1) to perform a zonal characterization of the biogeochemistry and biological diversity of the western tropical South Pacific during austral summer conditions, (2) to study the production and fate of organic matter (including carbon export) in... |
| Tipo: Text |
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| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00392/50324/51016.pdf |
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| Spungin, Dina; Belkin, Natalia; Foster, Rachel; Stenegren, Marcus; Caputo, Andrea; Pujo-pay, Mireille; Leblond, Nathalie; Dupouy, Cecile; Bonnet, Sophie; Berman-frank, Ilana. |
| The fate of diazotroph (N2 fixers) derived carbon (C) and nitrogen (N) and their contribution to vertical export of C and N in the Western Tropical South Pacific Ocean was studied in OUTPACE (Oligotrophy to UlTra-oligotrophy PACific Experiment). Our specific objective during OUTPACE was to determine whether autocatalytic programmed cell death (PCD) is an important mechanism affecting diazotroph mortality and a factor regulating the vertical flux of organic matter and thus the fate of the blooms. We sampled at three long duration (LD) stations of 5 days each (LDA, LDB, and LDC) where drifting sediment traps were deployed at 150, 325 and 500 m depths. LDA and LDB were characterized by high chlorophyll a (Chl a) concentrations (0.2–0.6 µg L−1) and dominated... |
| Tipo: Text |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00419/53048/53985.pdf |
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| Rousset, Guillaume; De Boissieu, Florian; Menkes, Christophe E.; Lefevre, Jerome; Frouin, Robert; Rodier, Martine; Ridoux, Vincent; Laran, Sophie; Bonnet, Sophie; Dupouy, Cecile. |
| Trichodesmium is the main nitrogen-fixing species in the South Pacific region, a hotspot for diazotrophy. Due to the paucity of in situ observations, methods for detecting Trichodesmium presence on a large scale have been investigated to assess the regional-to-global impact of these species on primary production and carbon cycling. A number of satellite-derived algorithms have been developed to identify Trichodesmium surface blooms, but determining with confidence their accuracy has been difficult, chiefly because of the scarcity of sea-truth information at time of satellite overpass. Here, we use a series of new cruises as well as airborne observational surveys in the South Pacific to quantify statistically the ability of these algorithms to discern... |
| Tipo: Text |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00419/53004/53953.pdf |
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| Saulia, Emmrick; Benavides, Mar; Henke, Britt; Turk-kubo, Kendra; Cooperguard, Haley; Grosso, Olivier; Desnues, Anne; Rodier, Martine; Dupouy, Cécile; Riemann, Lasse; Bonnet, Sophie. |
| Coastal and open ocean regions of the Western Tropical South Pacific ocean have been identified as a hotspot of N2 fixation. However, the environmental factors driving the temporal variability of abundance, composition, and activity of diazotrophs are still poorly understood, especially during the winter season. To address this, we quantified N2 fixation rates and the abundance of seven diazotroph phylotypes (UCYN-A1 symbiosis, UCYN-B, UCYN-C, Trichodesmium, Het-1, Het-2, and Het-3) on a monthly basis during two full years (2012 to 2014) at four stations along a coast to open ocean transect in the New Caledonian lagoon. The total nifH gene concentration (sum of all nifH gene copies) clearly decreased from the barrier reef to the shore. Apart from UCYN-B,... |
| Tipo: Text |
Palavras-chave: N-2 fixation; Diazotrophs; NifH; Abundance; New Caledonia. |
| Ano: 2020 |
URL: https://archimer.ifremer.fr/doc/00658/77027/78307.pdf |
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| Ganachaud, Alexandre; Cravatte, Sophie; Sprintall, Janet; Germineaud, Cyril; Alberty, Marion; Jeandel, Catherine; Eldin, Gerard; Metzl, Nicolas; Bonnet, Sophie; Benavides, Mar; Heimburger, Lars-eric; Lefevre, Jerome; Michael, Susanna; Resing, Joseph; Queroue, Fabien; Sarthou, Geraldine; Rodier, Martine; Berthelot, Hugo; Baurand, Francois; Grelet, Jacques; Hasegawa, Takuya; Kessler, William; Kilepak, Moyep; Lacan, Francois; Privat, Emilien; Send, Uwe; Van Beek, Pieter; Souhaut, Marc; Sonke, Jeroen E.. |
| The semi-enclosed Solomon Sea in the southwestern tropical Pacific is on the pathway of a major oceanic circuit connecting the subtropics to the equator via energetic western boundary currents. Waters transiting through this area replenish the Pacific Warm Pool and ultimately feed the equatorial current system, in particular the equatorial undercurrent. In addition to dynamical transformations, water masses undergo nutrient and micronutrient enrichment when coming in contact with the coasts, impacting the productivity of the downstream equatorial region. Broadscale observing systems are not well suited for describing the fine-scale currents and water masses properties in the Solomon Sea, leaving it relatively unexplored. Two multidisciplinary oceanographic... |
| Tipo: Text |
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| Ano: 2017 |
URL: https://archimer.ifremer.fr/doc/00390/50185/50808.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... |
| Tipo: Text |
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| Ano: 2018 |
URL: https://archimer.ifremer.fr/doc/00419/53003/53951.pdf |
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| Registros recuperados: 19 | |
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