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Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Volume 8, issue 7
Biogeosciences, 8, 1839–1852, 2011
https://doi.org/10.5194/bg-8-1839-2011
© Author(s) 2011. This work is distributed under
the Creative Commons Attribution 3.0 License.

Special issue: Interactions between planktonic organisms and the biogeochemical...

Biogeosciences, 8, 1839–1852, 2011
https://doi.org/10.5194/bg-8-1839-2011
© Author(s) 2011. This work is distributed under
the Creative Commons Attribution 3.0 License.

Research article 12 Jul 2011

Research article | 12 Jul 2011

Microbial food webs and metabolic state across oligotrophic waters of the Mediterranean Sea during summer

U. Christaki1, F. Van Wambeke2, D. Lefevre2, A. Lagaria1,3, L. Prieur4,8, M. Pujo-Pay5,6, J.-D. Grattepanche1, J. Colombet7, S. Psarra3, J. R. Dolan4,8, T. Sime-Ngando7, P. Conan5,6, M. G. Weinbauer4,8, and T. Moutin9 U. Christaki et al.
  • 1INSU-CNRS, UMR8187 LOG, Laboratoire d'Océanologie et des Géosciences, Université Lille Nord de France, ULCO, 32 avenue Foch, 62930 Wimereux, France
  • 2INSU-CNRS, UMR6117, LMGEM, Laboratoire de Microbiologie, Géochimie et Ecologie Marines, Université de la Méditerranée, Centre d'Océanologie de Marseille, Campus de Luminy Case 901, 13 288 Marseille cedex 9, France
  • 3Hellenic Centre for Marine Research, Institute of Oceanography, 71003 Heraklion, Crete, Greece
  • 4INSU-CNRS, UMR7093 LOV, Laboratoire d'Océanographie de Villefranche, Observatoire Océanologique de Villefranche-sur-Mer, 06 238 Villefranche-sur-Mer, France
  • 5INSU-CNRS, UMR7621, Lab. d'Océanographie Microbienne, Observatoire Océanologique, 66651 Banyuls/mer, France
  • 6UPMC Univ Paris 06, UMR7621, Laboratoire d'Océanographie Microbienne, Observatoire Océanologique, 66651 Banyuls/mer, France
  • 7INSU-CNRS, UMR6023, LMGE, Laboratoire Microorganismes: Génome et Environnement – 63177 Aubière cedex, France
  • 8UPMC Univ Paris 06, UMR7093, Laboratoire d'Océanographie de Villefranche, Observatoire Océanologique de Villefranche-sur-Mer, 06230 Villefranche-sur-Mer, France
  • 9INSU-CNRS, UMR6535, LOPB, Laboratoire d'Océanographie physique et biogéochimique Université de la Méditerranée, Centre d'Océanologie de Marseille, Campus de Luminy Case 901, 13 288 Marseille cedex 9, France

Abstract. The abundance and activity of the major members of the heterotrophic microbial community – from viruses to ciliates – were studied along a longitudinal transect across the Mediterranean Sea in the summer of 2008. The Mediterranean Sea is characterized by a west to-east gradient of deepening of DCM (deep chlorophyll maximum) and increasing oligotrophy reflected in gradients of biomass and production. However, within this well documented longitudinal trend, hydrological mesoscale features exist and likely influence microbial dynamics. Here we present data from a W-E transect of 17 stations during the period of summer stratification. Along the transect the production and fate of organic matter was investigated at three selected sites each one located in the centre of an anticyclonic eddy: in the Algero-Provencal Basin (St. A), the Ionian Basin (St. B), and the Levantine Basin (St. C). The 3 geographically distant eddies showed low values of the different heterotrophic compartments of the microbial food web, and except for viruses in site C, all integrated (0–150 m) stocks were higher in reference stations located in the same basin outside the eddies. During our study the 3 eddies showed equilibrium between GPP (Gross Primary Production) and DCR (Dark Community Respiration). Integrated PPp (Particulate Primary Production) values at A, B and C varied from ~140 to ~190 mg C m−2.

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