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Aquatic Microbial Ecology

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AME 56:1-12 (2009)  -  DOI:

Bacterial activity and diffusive nutrient supply in the oligotrophic Central Atlantic Ocean

Josep M. Gasol1,*, Evaristo Vázquez-Domínguez1, Dolors Vaqué1, Susana Agustí2, Carlos M. Duarte2

1Departament de Biologia Marina i d’Oceanografia, Institut de Ciències del Mar-CSIC. Pg. Marítim de la Barceloneta 39-47, 08003 Barcelona, Catalunya, Spain
2IMEDEA (CSIC-UIB), Institut Mediterrani d’Estudis Avançats, c. Miquel Marquès 21, 07190 Esporles, Mallorca, Spain

ABSTRACT: Growing evidence of inorganic nutrient limitation on oceanic bacteria suggests a global dependence of bacterial activity and production on rates of nutrient supply. The present study examined whether surface bacterial abundance is significantly related to water column stability, and whether bacterial activity and growth rate are related to the rate of diffusive supply of inorganic nutrients to the mixed layer in the Central Atlantic during 2 meridional cruises. The 2 cruises were run under very different oceanic conditions, with relatively low values of bacterial activity in spring 1995 and relatively higher values in fall 1995. We obtained depth-resolved data in the second cruise and found that the integrated value of bacterial production was also related to the rate of nutrient supply, while integrated particulate primary production and chlorophyll concentration were not. There was also no relationship between particulate primary production and bacterial production. The relationship between nutrient supply and integrated bacterial production was tested with data from a mesocosm experiment showing a good fit to the pattern obtained in the Atlantic. Average bacterial production was ~21% of primary production in the Central Atlantic, with values ranging between 5 and 100%, and higher values in the tropical areas. The demonstration of a direct relationship between nutrient supply and bacterial activity helps to explain a relatively large bacterial biomass as compared to phytoplankton biomass, a low bacterial growth efficiency, and a high bacterial carbon demand relative to contemporaneous primary production often measured in the open ocean, as well as the accumulation of dissolved organic carbon (DOC) observed in nutrient-limited oligotrophic seas.

KEY WORDS: Bacterial activity · Bacterial production · Central Atlantic · Nutrient supply · Primary production · Water column stability · Mediterranean mesocosms

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Cite this article as: Gasol JM, Vázquez-Domínguez E, Vaqué D, Agustí S, Duarte CM (2009) Bacterial activity and diffusive nutrient supply in the oligotrophic Central Atlantic Ocean. Aquat Microb Ecol 56:1-12.

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