Biogeosciences www.biogeosciences.net 1726-4170 1726-4189 5 6 2008 10.5194/bg-5-1751-2008 http://www.biogeosciences.net/5/1751/2008/ http://www.biogeosciences.net/5/1751/2008/bg-5-1751-2008.html http://www.biogeosciences.net/5/1751/2008/bg-5-1751-2008.pdf 1751 1764 2008-12-16 Role of environmental factors for the vertical distribution (0–1000 m) of marine bacterial communities in the NW Mediterranean Sea J. F. Ghiglione ghiglione@obs-banyuls.fr C. Palacios J. C. Marty G. Mével C. Labrune P. Conan M. Pujo-Pay N. Garcia M. Goutx CNRS, UMR7621, Lab. d'Océanographie Biologique de Banyuls, Avenue Fontaulé, BP44, 66650 Banyuls-sur-Mer, France UPMC Univ Paris 06, UMR 7621, Laboratoire ARAGO, Avenue Fontaulé, BP44, F66650 Banyuls-sur-Mer, France UMR 5244 CNRS UPVD EPHE, Biologie et Ecologie Tropicale et Méditerranéenne, Université de Perpignan Via Domitia, 52 Avenue Paul Alduy, 66860 Perpignan Cedex, France Observatoire Océanologique de Villefranche-sur-mer, Université Pierre et Marie Curie-Paris 6, Institut National des Sciences de l'Univers (INSU), CNRS (UMR 7093), BP 28, 06234 Villefranche sur mer, France CNRS, UMR 7144, Equipe de Chimie Marine, Station Biologique de Roscoff, 29682 Roscoff, France UPMC, Univ Paris 06, UMR 7144, Station Biologique de Roscoff, 29682 Roscoff, France UBO, Institut Universitaire Européen de la Mer, 29280 Plouzané, France Laboratoire de Microbiologie, Géochimie et Ecologie Marines, Université de la Méditerranée, Centre d'Océanologie de Marseille, CNRS (UMR 6117), Campus de Luminy, case 901, 13288 Marseille Cedex 09, France Bacterioplankton plays a central role in energy and matter fluxes in the sea, yet the factors that constrain its variation in marine systems are still poorly understood. Here we use the explanatory power of direct multivariate gradient analysis to evaluate the driving forces exerted by environmental parameters on bacterial community distribution in the water column. We gathered and analysed data from a one month sampling period from the surface to 1000 m depth at the JGOFS-DYFAMED station (NW Mediterranean Sea). This station is characterized by very poor horizontal advection currents which makes it an ideal model to test hypotheses on the causes of vertical stratification of bacterial communities. Capillary electrophoresis single strand conformation polymorphism (CE-SSCP) fingerprinting profiles analyzed using multivariate statistical methods demonstrated a vertical zonation of bacterial assemblages in three layers, above, in or just below the chlorophyll maximum and deeper, that remained stable during the entire sampling period. 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