AME 55:301-312 (2009)  -  DOI:

Bacterial colonization of transparent exopolymeric particles in mesocosms under different turbulence intensities and nutrient conditions

M. L. Pedrotti1,*, S. Beauvais1, M.-E. Kerros1, K. Iversen2, F. Peters3

1Marine Microbial Ecology Group, Laboratoire d’Océanographie de Villefranche, University of Paris VI, CNRS UMR 7093, Observatoire Océanologique de Villefranche-sur-Mer, Station Zoologique, BP 28, 06234 Villefranche-sur-Mer, France
2Department of Aquatic Biosciences, Norwegian College of Fishery Science, University of Tromsø, Breivika,
9037 Tromsø, Norway
3Institut de Ciències del Mar, CMIMA (CSIC) Passeig Maritim de la Barceloneta, 08003 Barcelona, Catalunya, Spain

ABSTRACT: We examined bacterial colonization of transparent exopolymeric particles (TEP) in nutrient-manipulated mesocosms subjected to different turbulence intensities. We quantified heterotrophic bacterial abundance, production and diversity using fluorescence in situ hybridization (FISH). The abundance of attached bacteria increased significantly with TEP size in all treatments. The slope values of the number of bacteria scaled with TEP size varied from 1.15 on Day 1 to 2.04 on Day 11 in still and turbulent tanks, respectively. Comparison between these slopes indicated that the number of attached bacteria for a given TEP diameter was higher under turbulence. The addition of nutrients and turbulence in mesocosms neither supported higher bacterial abundance nor resulted in a correlation between bacterial concentrations and TEP. However, in enriched turbulent tanks, the number of attached bacteria was higher and was linked to rapid TEP formation after the diatom bloom. This was accompanied by higher bacterial production (1.21 µmol C l–1 d–1 at the intermediate level of turbulence on Day 9), which was positively related to TEP. These correlations highlight the finding that higher bacterial productivity was due to a larger fraction of attached bacteria (up to 56.4%). Changes in bacterial production occurred with simultaneous changes in the community structure, i.e. the percentages of the Cytophaga-Flavobacteria-Bacteroides cluster increased significantly. By Day 9, this cluster became the dominant group of bacteria attached to TEP (85 and 90%, respectively at intermediate and high levels of turbulence). Among the marine heterotrophic bacterioplankton, this phylum is known to be common as attached bacteria. Therefore, it seems that the added nutrients and subsequent TEP production can be used by bacteria more efficiently under turbulent conditions through a shift in group-specific composition towards more attached bacteria with higher production rates.

KEY WORDS:Transparent exopolymer particles · Particle colonization · Bacteria · FISH · Turbulence · Nutrients · Mesocosms

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Cite this article as: Pedrotti ML, Beauvais S, Kerros ME, Iversen K, Peters F (2009) Bacterial colonization of transparent exopolymeric particles in mesocosms under different turbulence intensities and nutrient conditions. Aquat Microb Ecol 55:301-312.

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