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Auteur Pringault, O.; Tesson, S.; Rochelle-Newall, E. url  doi
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  Titre Respiration in the Light and Bacterio-Phytoplankton Coupling in a Coastal Environment Type Article scientifique
  Année 2009 Publication Revue Abrégée Microb. Ecol.  
  Volume 57 Numéro 2 Pages 321-334  
  Mots-Clés bacteria; dissolved organic-carbon; enhanced dark; growth efficiency; heterotrophic; marine bacterioplankton; nw mediterranean sea; post-illumination respiration; respiration; salt-marsh estuaries; solar; ultraviolet-radiation; uv-radiation  
  Résumé In pelagic ecosystems, the principal source of organic matter is via autotrophic production and the primary sink is through heterotrophic respiration. One would therefore anticipate that there is some degree of linkage between these two compartments. Recent work has shown that respiration in the light is higher than dark respiration. Consequently, many of the methods used to determine respiration and production are biased as they require the assumption that light and dark respiration rates are equivalent. We show here that, in a coastal ecosystem, under visible light exposure, respiration in the light is related to gross production. More than 60% of the variation of respiration in the light, measured at 1 to 40 A mu g L(-1) of chlorophyll a (Chla), could be explained by the variations of gross production. Secondly, the relative contribution of bacterial respiration to community respiration in the light represented up to 79% at low Chla (1 A mu g L(-1)) and was negatively correlated with Chla concentration. Although bacterial production and bacterial respiration were both enhanced in the light, bacterial respiration in the light was more stimulated than bacterial production, which resulted in a decrease in bacterial growth efficiency during light exposure. These results show that the impact of light on the functioning of the microbial loop needs to be taken into account for a better understanding of the oceanic carbon cycle.  
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  Langue English Langue du Résumé Titre Original (up)  
  Éditeur de collection Titre de collection Titre de collection Abrégé  
  Volume de collection Numéro de collection Edition  
  ISSN 0095-3628 ISBN Médium  
  Région Expédition Conférence  
  Notes Approuvé pas de  
  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 826  
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Auteur Pagès, R.; Baklouti, M.; Barrier, N.; Richon, C.; Dutay, J.-C.; Moutin, T. doi  openurl
  Titre Changes in rivers inputs during the last decades significantly impacted the biogeochemistry of the eastern Mediterranean basin: A modelling study Type Article scientifique
  Année 2020 Publication Revue Abrégée Prog. Oceanogr.  
  Volume 181 Numéro Pages 102242  
  Mots-Clés Biogeochemistry; Coupled physical-biogeochemical model; ecosystem changes; Flexible stoichiometry model; Mediterranean Sea; nitrogen; Nutrient; nutrients; organic-carbon; phosphate; phosphorus limitation; phytoplankton; primary productivity; River inputs; sea; western  
  Résumé The Mediterranean Sea (MS) is a semi-enclosed sea characterized by a zonal west-east gradient of oligotrophy, where microbial growth is controlled by phosphate availability in most situations. External inputs of nutrients including Gibraltar inputs, river inputs and atmospheric deposition are therefore of major importance for the biogeochemistry of the MS. The latter has long been considered to be driven mainly by nutrient exchanges at Gibraltar. However, recent studies indicate that river inputs significantly affect nutrients concentrations in the Mediterranean Sea, although their resulting impact on its biogeochemistry remains poorly understood. In this study, our aim was to help fill this knowledge gap by addressing the large-scale and long-term impact of variations in river inputs on the biogeochemistry of the Mediterranean Sea over the last decades, using a coupled physical-biogeochemical 3D model (NEMO-MED12/Eco3M-Med). As a first result, it has been shown by the model that the strong diminution (60%) of phosphate (PO4) in river inputs into the Mediterranean Sea since the end of the 1980s induced a significant lowering of PO4 availability in the sub-surface layer of the Eastern Mediterranean Basin (EMB). One of the main consequences of PO4 diminution is the rise, never previously documented, of dissolved organic carbon (DOC) concentrations in the surface layer (by 20% on average over the EMB). Another main result concerns the gradual deepening of the top of the phosphacline during the period studied, thus generating a shift between the top of the nitracline and the top of the phosphacline in the EMB. This shift has already been observed in situ and documented in literature, but we propose here a new explanation for its occurrence in the EMB. The last main result is the evidence of the decline in abundance and the reduction of size of copepods calculated by the model over the years 1985-2010, that could partially explain the reduction in size of anchovy and sardine recently recorded in the MS. In this study, it is shown for the first time that the variations in river inputs that occurred in the last decades may have significantly altered the biogeochemical cycles of two key elements (P and C), in particular in the EMB. To conclude, the magnitude of the biogeochemical changes induced by river inputs and runoff alone over the last thirty years clearly calls for the use of realistic scenarios of river inputs along with climate scenarios for coupled physical-biogeochemical forecasts in the MS.  
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  Langue English Langue du Résumé Titre Original (up)  
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  Volume de collection Numéro de collection Edition  
  ISSN 0079-6611 ISBN Médium  
  Région Expédition Conférence  
  Notes WOS:000512481200014 Approuvé pas de  
  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 2757  
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Auteur Pringault, O.; Lafabrie, C.; Avezac, M.; Bancon-Montigny, C.; Carré, C.; Chalghaf, M.; Delpoux, S.; Duvivier, A.; Elbaz-Poulichet, F.; Gonzalez, C.; Got, P.; Leboulanger, C.; Spinelli, S.; Hlaili, A.S.; Bouvy, M. doi  openurl
  Titre Consequences of contaminant mixture on the dynamics and functional diversity of bacterioplankton in a southwestern Mediterranean coastal ecosystem Type Article scientifique
  Année 2016 Publication Revue Abrégée Chemosphere  
  Volume 144 Numéro Pages 1060-1073  
  Mots-Clés aquatic systems; Bacterial growth efficiency; Bacterial production; bizerte lagoon; Community level physiological profiles; growth efficiency; Herbicides; heterotrophic bacteria; Metals; microbial communities; Microcosms; organic-carbon; polycyclic aromatic-hydrocarbons; sediment resuspension; substrate utilization pattern; surface sediments  
  Résumé Contamination of coastal environments is often due to a complex mixture of pollutants, sometimes in trace levels, that may have significant effects on diversity and function of organisms. The aim of this study was to evaluate the short-term dynamics of bacterioplankton exposed to natural and artificial mixtures of contaminants. Bacterial communities from a southwestern Mediterranean ecosystem, lagoon and the bay (offshore) of Bizerte were exposed to i) elutriate from resuspension of contaminated sediment, and ii) an artificial mixture of metals and herbicides mimicking the contamination observed during sediment resuspension. Elutriate incubation as well as artificial spiking induced strong enrichments in nutrients (up to 18 times), metals (up to six times) and herbicides (up to 20 times) relative to the in situ concentrations in the offshore station, whereas the increases in contaminants were less marked in the lagoon station. In the offshore waters, the artificial mixture of pollutants provoked a strong inhibition of bacterial abundance, production and respiration and significant modifications of the potential functional diversity of bacterioplankton with a strong decrease of the carbohydrate utilization. In contrast, incubation with elutriate resulted in a stimulation of bacterial activities and abundances, suggesting that the toxic effects of pollutants were modified by the increase in nutrient and DOM concentrations due to the sediment resuspension. The effects of elutriate and the artificial mixture of pollutants on bacterial dynamics and the functional diversity were less marked in the lagoon waters, than in offshore waters, suggesting a relative tolerance of lagoon bacteria against contaminants. (C) 2015 Elsevier Ltd. All rights reserved.  
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  Langue English Langue du Résumé Titre Original (up)  
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  Volume de collection Numéro de collection Edition  
  ISSN 0045-6535 ISBN Médium  
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  Numéro d'Appel MARBEC @ isabelle.vidal-ayouba @ collection 1507  
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