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Heterotrophic bacterial production in the South East Pacific: longitudinal trends and coupling with primary production
1Laboratoire de Microbiologie, Géologie et Ecologie Marine (LMGEM), CNRS UMR 6117, Université de la Méditerranée, Campus de Luminy – Case 901, 13288 Marseille cedex 9, France
2Laboratoire d'Océanographie et de Biogéochimie (LOB), CNRS UMR 6535, Université de la Méditerranée, Campus de Luminy – Case 901, 13288 Marseille cedex 9, France
3Laboratoire d'Océanographie Biologique de Banyuls (LOBB), Université Pierre et Marie Curie – Paris VI, CNRS UMR7621, BP 44, F66650 Banyuls-sur-Mer, France
4Department of Oceanography & Center for Oceanographic Research in the eastern South Pacific, University of Concepcion, Casilia 160-C, Concepcion, Chile
5CNRS, Laboratoire d'océanographie de Villefranche, 06230 Villefranche-sur-Mer, France ; Université Pierre et Marie Curie-Paris6, Laboratoire d'océanographie de Villefranche, 06230 Villefranche-sur-Mer, France
Abstract. Spatial variations of heterotrophic bacterial production and phytoplankton primary production were investigated across South East Pacific Ocean (–141° W, –8° S to –72° W, –35° S) in November–December 2004. Bacterial production (³H leucine incorporation) integrated over the euphotic zone encompassed a wide range of values, from 43 mg C m−2 d−1 in the hyper-oligotrophic South Pacific Gyre to 392 mg C m−2 d−1 in the upwelling off Chile. Within the gyre (120° W, 22° S) records of low phytoplankton biomass (7 mg TChla m−2) were obtained and in situ 14C based particulate primary production rates were as low as 153 mg C m−2 d−1, thus equal to the value considered as a limit for primary production under strong oligotrophic conditions. In the South Pacific gyre average rates of ³H leucine incorporation rates, and leucine incorporation rates per cell (5–21 pmol L−1 h−1 and 15–56×10−21 mol cell−1 h−1, respectively), were in the same range as those reported for other oligotrophic sub tropical and temperate waters. Rates of dark community respiration, determined at selected stations across the transect varied in a narrow range (42–97 mmol O2 m−2 d−1), except for one station in the upwelling off Chile (245 mmol O2 m−2 d−1). Bacterial growth efficiencies varied between 5 and 38% and bacterial carbon demand largely exceeded 14C particulate primary production across the South Pacific Ocean. Net community production also revealed negative values in the South Pacific Gyre (–13±20 to –37±40 mmol O2 m−2 d−1). Such imbalances being impossible in this area far from any external input, we discuss the techniques involved for determining the coupling between primary production and bacterial heterotrophic production.
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Citation: Van Wambeke, F., Obernosterer, I., Moutin, T., Duhamel, S., Ulloa, O., and Claustre, H.: Heterotrophic bacterial production in the South East Pacific: longitudinal trends and coupling with primary production, Biogeosciences Discuss., 4, 2761-2791, 2007. Bibtex EndNote Reference Manager
