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Aquatic Microbial Ecology

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AME 46:43-53 (2007)  -  doi:10.3354/ame046043

Bacterial assemblage structure and carbon metabolism along a productivity gradient in the NE Atlantic Ocean

Laura Alonso-Sáez1,*, Javier Arístegui2, Jarone Pinhassi3, Laura Gómez-Consarnau3, José M. González4, Dolors Vaqué1, Susana Agustí5, Josep M. Gasol1

1Departament de Biologia Marina i Oceanografia, Institut de Ciències del Mar—CSIC, Pg. Marítim de la Barceloneta 37–49, 08003 Barcelona, Catalunya, Spain
2Departamento de Biología, Universidad de las Palmas de Gran Canaria, Campus Universitario de Tafira, PO Box 550, 35017 Las Palmas de Gran Canaria, Spain
3Marine Microbiology, Department of Biology and Environmental Sciences, University of Kalmar, Barlastgatan 11, 39182 Kalmar, Sweden
4Departamento de Microbiología y Biología Celular, Facultad de Farmacia, Universidad de La Laguna, Avda. Astrofísico Francisco Sánchez s/n 38071 La Laguna, Tenerife, Spain 5Institut Mediterrani d’Estudis Avançats (IMEDEA), CSIC-Universitat de les Illes Balears, Miquel Marquès, 21, 07190 Esporles, Mallorca, Spain

ABSTRACT: Bacterioplankton have the potential to significantly affect the cycling of organic matter in the ocean; however, little is known about the linkage between bacterial assemblage structure and carbon metabolism. In this study, we investigated whether changes in the phylogenetic composition of bacterioplankton were associated with changes in bacterial carbon processing (bacterial production, respiration and biomass) in the subtropical NE Atlantic Ocean. We found consistent differences in the composition of the bacterial assemblage, as revealed by denaturing gradient gel electrophoresis (DGGE) and catalyzed reporter deposition-fluorescence in situ hybridization (CARD-FISH), along a gradient from the NW African upwelling to the oligotrophic North Atlantic Subtropical Gyre. The percent contribution of Bacteroidetes, Roseobacter and Gammaproteobacteria significantly increased towards more productive waters, whereas the SAR11 clade of the Alphaproteobacteria remained relatively constant (average 28% of DAPI-stained cells) throughout the area. Changes in the composition of the bacterial assemblage detected by DGGE were weakly but significantly correlated with changes in carbon processing variables. The abundances of Roseobacter and Gammaproteobacteria were highly correlated with the concentration of particulate organic carbon and chlorophyll a, reflecting the affinity of these groups to nutrient-enriched conditions. The abundance of Roseobacter was also positively correlated with heterotrophic bacterial production, suggesting their active participation in carbon processing.

KEY WORDS: Bacteria · Atlantic Ocean · Diversity · Metabolism · CARD-FISH · DGGE

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