Revisited phytoplanktonic carbon dependency of heterotrophic bacteria in freshwaters, transitional, coastal and oceanic waters

Authors

  • Eric Fouilland,

    1. Laboratoire Ecosystèmes lagunaires, ECOLAG, UMR 5119 (CNRS, Université Montpellier 2, IFREMER, IRD), Montpellier and Sète, France
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  • Behzad Mostajir

    1. Laboratoire Ecosystèmes lagunaires, ECOLAG, UMR 5119 (CNRS, Université Montpellier 2, IFREMER, IRD), Montpellier and Sète, France
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  • Editor: Ian Head

Correspondence: Eric Fouilland, Laboratoire Ecosystèmes lagunaires, ECOLAG, UMR 5119 (CNRS, Université Montpellier 2, IFREMER, IRD), Station Marine de l'Environnement Littoral, 2 Rue des Chantiers, 34200 Sète, France. Tel.: +33 4 67 46 33 85; fax: +33 4 67 46 33 99; e-mail: eric.fouilland@univ-montp2.fr

Abstract

Positive relationships between heterotrophic bacteria and particulate phytoplankton production (respectively, BP and PPP) have been reported for several areas, suggesting that material produced by phytoplankton was a major substrate for bacterial growth. Since then, thousands of simultaneous measurements of both PPP and BP have been performed. A review of these data showed that BP may exceed PPP considerably (median ranged between 132% and 484%) in all aquatic systems with the lowest PPP. In oceanic waters, BP did not seem to be temporally synchronized with PPP and the median BP : PPP ratio is 15% with moderate PPP, but the immediate bacterial carbon (C) demand (including bacterial respiration) was greater than the corresponding total primary production (i.e. dissolved and particulate primary production) for >80% of both volumetric and areal datasets. In freshwaters, the strong covariation observed between BP and PPP seemed mainly due to a common response to sudden nutrient inputs into enclosed systems, leading to a similar range of production rates and temporal synchronicities. Indeed, phytoplankton exudates contributed directly to only 32% (median) of BP when C-tracking experiments were performed in freshwaters. Therefore, because direct C dependency of bacteria on phytoplankton is questionable, other C sources might be more significant for bacterial growth.

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