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Interférence entre les processus mitotiques et la prise d'azote chez Thalassiosira weissflogii. Implications en modélisation et sur les flux globaux.

Christophe Mocquet 1, 2
2 COMORE - Modeling and control of renewable resources
LOV - Laboratoire d'océanographie de Villefranche, CRISAM - Inria Sophia Antipolis - Méditerranée
Abstract : The Monod model of nitrogen acquisition, originally used to represent the effect of a nutrient concentration on the phytoplankton uptake rate, is inadequate when other factors show temporal variations. Literature generally links the diurnal oscillations of nitrogen acquisition to a response of the physiological status of microalgae to the photon flux and to the substrate availability. This thesis aims to analyze how the cell cycle is also a significant determinant of nitrogen acquisition, and where appropriate, to assess the impact of this property at the macroscopic level. In this purpose, we conducted continuous culture experiments of the diatom Thalassiosira weissflogii exposed to various conditions of light and nitrogen supply. Results reveal a decrease in nitrogen acquisition when a significant proportion of the population is in mitosis. The timing of the mitotic processes appears to be regulated both by the growth conditions and by an internal clock. Moreover, our experiments show that the emergent behavior of the individuals depends on the degree of synchronization the population, and we discuss the factors affecting this phenomenon. Then, our hypotheses are used in a numerical approach in order to assess the gain of representativeness obtained by taking into account the cell cycle in phytoplankton growth models. Finally, we discuss how the cell cycle may impact nitrogen acquisition in the real marine environment and conclude on the possible implications in ecology.
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Submitted on : Monday, April 12, 2010 - 3:09:38 PM
Last modification on : Friday, February 4, 2022 - 3:20:48 AM
Long-term archiving on: : Tuesday, September 14, 2010 - 6:24:55 PM

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Christophe Mocquet. Interférence entre les processus mitotiques et la prise d'azote chez Thalassiosira weissflogii. Implications en modélisation et sur les flux globaux.. Océan, Atmosphère. Université Pierre et Marie Curie - Paris VI, 2009. Français. ⟨tel-00472581⟩

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