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| L'Helguen, S.; Le Corre, P.. |
| Les quantités d'éléments nutritifs, en particulier d'azote, et de matière organique déversées par les fleuves dans les eaux côtières ont considérablement augmenté ces dernières années en raison d'une part d'une intensification des pratiques agricoles, d'autre part, d'une industrialisation et d'une urbanisation croissante des zones littorales. Ces apports peuvent, à une échelle locale ou à mésoéchelle, modifier de manière importante le fonctionnement des écosystèmes côtiers. Ils peuvent, en particulier, en enrichissant le milieu en azote intensifier les processus d'absorption du phytoplancton et déclencher des proliférations algales. La dégradation et la minéralisation de la matière organique ainsi produite et aussi de la matière organique directement... |
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| Ano: 1994 |
URL: http://archimer.ifremer.fr/doc/00106/21682/19261.pdf |
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| Ternon, E.; Guieu, C.; Ridame, C.; L'Helguen, S.; Catala, P.. |
| The Mediterranean Sea is a semi-enclosed basin characterized by a strong thermal stratification during summer during which the atmosphere is the main source of new nutrients to the nutrient-depleted surface layer. From aerosol sampling and microcosm experiments performed during the TransMed BOUM cruise (June-July 2008) we showed that: (i) the Mediterranean atmosphere composition (Al, Fe, P) was homogeneous over similar to 28 degrees of longitude and was a mixture with a constant proportion of anthropogenic contribution and a variable but modest contribution of crustal aerosols. This quite stable composition over a one month period and a long transect (similar to 2500 km) allowed to define the Mediterranean atmospheric "background" that characterizes the... |
| Tipo: Text |
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| Ano: 2011 |
URL: http://archimer.ifremer.fr/doc/00133/24399/22405.pdf |
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| Salt, Lesley A.; Beaumont, L.; Blain, S.; Bucciarelli, E.; Grossteffan, E.; Guillot, A.; L'Helguen, S.; Merlivat, L.; Repecaud, Michel; Quemener, Loic; Rimmelin-maury, P.; Treguer, P.; Bozec, Y.. |
| From 2008 to 2014, the MAREL-Iroise buoy, located in the Bay of Brest, collected high-frequency measurements of partial pressure of CO2 (pCO2) and ancillary hydrographic parameters, in conjunction with a comprehensive sampling regime of two additional carbonate system variables total alkalinity (AT), and dissolved inorganic carbon (DIC). Biological processes drive variations in AT and DIC throughout the year, except in winter, when primary production is negligible and large freshwater inputs occur. Annually, the Bay of Brest generally behaves as a source of CO2 to the atmosphere (0.14 ± 0.20 mol C m− 2 yr− 1), showing inter-annual variability significantly linked to annual net community production (NCP). The presence of a large community of benthic filter... |
| Tipo: Text |
Palavras-chave: Bay of Brest; Carbonate system; Dissolved inorganic carbon; Total alkalinity. |
| Ano: 2016 |
URL: https://archimer.ifremer.fr/doc/00350/46157/45855.pdf |
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| Berthelot, H; Moutin, T.; L'Helguen, S.; Leblanc, K.; Helias, S.; Grosso, O.; Leblond, N.; Charriere, B.; Bonnet, S.. |
| In the oligotrophic ocean characterized by nitrate (NO3-) depletion in surface waters, dinitrogen (N-2) fixation and dissolved organic nitrogen (DON) can represent significant nitrogen (N) sources for the ecosystem. In this study, we deployed large in situ mesocosms in New Caledonia in order to investigate (1) the contribution of N-2 fixation and DON use to primary production (PP) and particle export and (2) the fate of the freshly produced particulate organic N (PON), i.e., whether it is preferentially accumulated and recycled in the water column or exported out of the system. The mesocosms were fertilized with phosphate (PO43-) in order to prevent phosphorus (P) limitation and promote N-2 fixation. The diazotrophic community was dominated by... |
| Tipo: Text |
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| Ano: 2015 |
URL: https://archimer.ifremer.fr/doc/00275/38672/73173.pdf |
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| Ridame, C.; Dekaezemacker, J.; Guieu, C.; Bonnet, S.; L'Helguen, S.; Malien, F.. |
| The response of the phytoplanktonic community (primary production and algal biomass) to contrasted Saharan dust events (wet and dry deposition) was studied in the framework of the DUNE ("a DUst experiment in a low-Nutrient, low-chlorophyll Ecosystem") project. We simulated realistic dust deposition events (10 gm(-2)) into large mesocosms (52m(3)). Three distinct dust addition experiments were conducted in June 2008 (DUNE-1-P: simulation of a wet deposition; DUNE-1-Q: simulation of a dry deposition) and 2010 (DUNE-2-R1 and DUNE-2-R2: simulation of two successive wet depositions) in the northwestern oligotrophic Mediterranean Sea. No changes in primary production (PP) and chlorophyll a concentrations (Chl a) were observed after a dry deposition event, while... |
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| Ano: 2014 |
URL: https://archimer.ifremer.fr/doc/00216/32741/31144.pdf |
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