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www.biogeosciences.net/6/705/2009/
doi:10.5194/bg-6-705-2009
© Author(s) 2009. This work is distributed
under the Creative Commons Attribution 3.0 License.
Bottom up effects on bacterioplankton growth and composition during summer-autumn transition in the open NW Mediterranean Sea
1Laboratoire de Microbiologie, Géochimie et Ecologie Marines, CNRS, Université de la Méditerranée, Centre d'Océanologie de Marseille, UMR6117, Campus de Luminy, case 901, 13 288 Marseille Cedex 09, France
2CNRS, UMR7621, Laboratoire d'Océanographie Biologique de Banyuls, Avenue Fontaulé, BP 44, 66 650 Banyuls-sur-Mer, France
3UPMC Univ Paris 06, UMR7621, Laboratoire ARAGO, Avenue Fontaulé, BP 44, 66 650 Banyuls-sur-Mer, France
4Biological Centre of the Academy of Sciences of the Czech Republic, Hydrobiological Institute, Na sádkách 7, 37005 České Budějovice, Czech Republic
5CNRS, UMR7144, Equipe de Chimie Marine, Station Biologique de Roscoff, 29 682 Roscoff, France
6UPMC Univ Paris 06, Equipe de Chimie Marine, Station Biologique de Roscoff, 29 682 Roscoff, France
Abstract. We examined the vertical and temporal dynamics of nutrients, ectoenzymatic activities under late summer-fall transition period (September–October 2004) in NW Mediterranean Sea in relation to temporal change in factors limiting bacterial production. The depth of the mixed layer (12.8±5.3 m) was extremely stable until the onset of the destratification period after 11 October, creating a zone where diffusion of nutrient from the much deeper phosphacline (69±12 m) and nitracline (50±8 m) was probably strongly limited. However after 1st October, a shallowing of nutriclines occured, particularly marked for nitracline. Hence, the nitrate to phosphate ratio within the mixed layer, although submitted to a high short term variability, shifted the last week of the cruise from 1.1±1.2 to 4.6±3.8, and nitrate increased by a factor 2 (0.092±0.049 μM). A corresponding switch from more than one limitation (PN) to P-only limitation of bacterial production was observed during the month as detected by enrichment bioassays. Differences in the identity of the limiting nutrient in surface (5 m: N and P at the beginning, strictly P at the end of the study) versus 80 m (labile carbon) influence greatly bacterial community structure shift between these two layers. The two communities (5 and 80 m) reacted rapidly (24 h) to changes in nutrient concentrations by drastic modification of total and active population assemblages resulting in changes in activity. For bacterial production values less than 10 ng C l−1 h−1 (associated to deeper layers), aminopeptidase and lipase exhibited higher activity relative to production whereas phosphatase varied in the same proportions than BP on the range of activities tested. Our results illustrate the effect of bottom-up control on bacterial community structure and activities in the epipelagic NW Mediterranean Sea.
Final Revised Paper (PDF, 1310 KB) Discussion Paper (BGD) Special Issue
Citation: Van Wambeke, F., Ghiglione, J.-F., Nedoma, J., Mével, G., and Raimbault, P.: Bottom up effects on bacterioplankton growth and composition during summer-autumn transition in the open NW Mediterranean Sea, Biogeosciences, 6, 705-720, doi:10.5194/bg-6-705-2009, 2009. Bibtex EndNote Reference Manager XML
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