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Biogeosciences An interactive open-access journal of the European Geosciences Union
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https://doi.org/10.5194/bg-2017-426
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2017-426
© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.

Submitted as: research article 23 Oct 2017

Submitted as: research article | 23 Oct 2017

Review status
This discussion paper is a preprint. It has been under review for the journal Biogeosciences (BG). The manuscript was not accepted for further review after discussion.

Dissolved organic matter release by phytoplankton in the context of the Dynamic Energy Budget theory

Eleni Livanou1,2, Anna Lagaria2, Stella Psarra2, and Konstadia Lika1 Eleni Livanou et al.
  • 1Department of Biology, University of Crete, 70013 Heraklion, Greece
  • 2Hellenic Centre for Marine Research, Institute of Oceanography, 71500 Heraklion, Greece

Abstract. Extracellular release of dissolved organic matter (DOM) by phytoplankton is a significant process that drives the microbial loop, providing energy and nutrients to bacteria. In this paper, a dynamic energy budget model is proposed for describing DOM release by phytoplankton under nitrogen and phosphorus limiting conditions. The model allows for the distinction of the two major mechanisms of DOM release; passive diffusion related to growth and lysis of the cells and active exudation related to rejection of unprocessed substrates due to stoichiometric constraints. Model results suggest that phosphorus deficiency has less severe effect on phytoplankton growth and primary production (PP) rate than nitrogen deficiency, while co-limitation by both nutrients has the most severe effect. The dependence of dissolved organic carbon (DOC) release rate on the cellular carbohydrates concentration is also highlighted by the model. Furthermore, model predictions resolve the relationship between PP and DOC release under different nutrient availability scenarios, providing a possible explanation for the deviations from 1 : 1 linear relationship between PP and DOC release, often observed in oligotrophic systems. This deviation is a result of the prevalence of the active exudation mechanism and the reduction of the PP rate due to nutrient limitation. Conversely, passive diffusion is more important under nutrient-replete conditions. The different relative contributions of the two mechanisms result in different qualities of DOM produced by phytoplankton in terms of elemental and molecular composition and size fractions, with potential implications for the bioavailability of the produced DOM for bacteria and the coupling of phytoplankton-bacteria dynamics.

Eleni Livanou et al.
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AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
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Interactive discussion
Status: closed
Status: closed
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
Printer-friendly Version - Printer-friendly version Supplement - Supplement
Eleni Livanou et al.
Eleni Livanou et al.
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Short summary
A model quantifying the two conceptual mechanisms of dissolved organic matter (DOM) release by phytoplankton, namely passive diffusion and active exudation, under different nutrient availability scenarios is proposed. The model resolves the relationship between primary production and DOM release, which depends on nutrient availability and predicts the production of DOM with different molecular and elemental ratio signatures, with potential implications for phytoplankton–bacteria relationships.
A model quantifying the two conceptual mechanisms of dissolved organic matter (DOM) release by...
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