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Bacterioplankton groups involved in the uptake of phosphate and dissolved organic phosphorus in a mesocosm experiment with P-starved Mediterranean waters

Authors

  • Marta Sebastián,

    Corresponding author
    1. Departament de Biologia Marina i Oceanografia, Institut de Ciències del Mar, CSIC, Pg Marítim de la Barceloneta 37-49, E08003 Barcelona, Catalunya, Spain
      E-mail: msebastian@icm.csic.es; Tel. +34 93 2309500; Fax +34 93 2309555.
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  • Paraskevi Pitta,

    1. Hellenic Centre for Marine Research, Oceanography Institute, P.O. Box 2214, 71003 Heraklion, Crete, Greece
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  • José M. González,

    1. Department of Microbiology, University of La Laguna, ES-38206 La Laguna, Tenerife, Spain
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  • T. Frede Thingstad,

    1. Department of Biology, University of Bergen, P.O. Box 7803, 5020 Bergen, Norway.
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  • Josep M. Gasol

    1. Departament de Biologia Marina i Oceanografia, Institut de Ciències del Mar, CSIC, Pg Marítim de la Barceloneta 37-49, E08003 Barcelona, Catalunya, Spain
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E-mail: msebastian@icm.csic.es; Tel. +34 93 2309500; Fax +34 93 2309555.

Summary

The use of inorganic phosphate (Pi) and dissolved organic phosphorus (DOP) by different bacterial groups was studied in experimental mesocosms of P-starved eastern Mediterranean waters in the absence (control mesocosms) and presence of additional Pi (P-amended mesocosms). The low Pi turnover times in the control mesocosms and the increase in heterotrophic prokaryotic abundance and production upon Pi addition confirmed that the bacterial community was originally P-limited. The bacterioplankton groups taking up Pi and DOP were identified by means of microautoradiography combined with catalysed reporter deposition fluorescence in situ hybridization. Incubations with leucine were also performed for comparative purposes. All the probe-identified groups showed a high percentage of cells taking up Pi and DOP in the control, P-limited, mesocosms throughout the experiment. However, in response to Pi addition two contrasting scenarios in Pi use were observed: (i) on day 1 of the experiment Pi addition caused a clear reduction in the percentage of SAR11 cells taking up Pi, whereas Gammaproteobacteria, Roseobacter and Bacteroidetes showed similar percentages to the ones in the control mesocosms and (ii) on day 4 of the experiment, probably when the bacterial community had fully responded to the P input, all the probe-identified groups showed low percentages of cells taking up the substrate as compared with the control mesocosms. These differences are likely related to different P requirements among the bacterial groups and point out to the existence of two contrasting strategies in P use.

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