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Short-term temporal variations of heterotrophic bacterial abundance and production in the open NW Mediterranean Sea
1CNRS, UMR 7144, Equipe de Chimie Marine, Station Biologique de Roscoff, 29682 Roscoff, France
2UPMC, Univ. Paris 06, UMR 7144, Station Biologique de Roscoff, 29682 Roscoff, France
3UBO, Institut Universitaire Européen de la Mer, 29280 Plouzané, France
4CNRS, UMR 7621, Laboratoire d'Océanographie Biologique de Banyuls, Avenue Fontaulé, BP44, 66650 Banyuls sur mer, France
5UPMC, Univ. Paris 06, UMR 7621, Laboratoire ARAGO, Avenue Fontaulé, BP 44, 66650 Banyuls sur mer, France
Abstract. We present the vertical and temporal dynamics of total vs. particle-attached bacterial abundance and activity over a 5 week period under summer to autumn transition in NW Mediterranean Sea. By comparison to previous investigations in the same area but during different seasons, we found that total bacterial biomass and production values were consistent with the hydrological conditions of the summer-fall transition. At a weekly time scale, total bacterial biomass and production in the euphotic layers was significantly correlated with phytoplanktonic biomass. At an hourly time scale, total bacterial biomass responded very rapidly to chlorophyll-a fluctuations, suggesting a tight coupling between phytoplankton and bacteria for resource partitioning during summer-autumn transition. In contrast, no influence of diel changes on bacterial parameters was detected. Episodic events such as coastal water intrusions had a significant positive effect on total bacterial abundance and production, whereas we could not detect any influence of short wind events whatever the magnitude. Finally, we show that particle-attached bacteria can represent a large proportion (until 49%) of the total bacterial activity in the euphotic layer but display rapid and sporadic changes at hourly time scales. This study underlines the value of large datasets covering different temporal scales to clarify the biogeochemical role of bacteria in the cycling of organic matter in open seawater.
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Citation: Mével, G., Vernet, M., and Ghiglione, J. F.: Short-term temporal variations of heterotrophic bacterial abundance and production in the open NW Mediterranean Sea, Biogeosciences Discuss., 5, 1899-1932, 2008. Bibtex EndNote Reference Manager
