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Theses

Impact de la température sur le phytoplancton et ses interactions avec les virus

Abstract : Climate changes induced by human activities will deeply impact natural ecosystems. Marine ecosystems, leaving in a highly variable environment, are therefore threatened. Within these communities, phytoplankton have a primordial role in the trophic web and in the regulation of climate processes. Understanding the evolution of these communities in a warming world is an issue of oceanography. Among factor affecting phytoplankton dynamics, viruses play a key role through their capacity to lyse their hosts. They are therefore controlling the phytoplankton population dynamics. It is then crucial to understand how the viruses impact will evolve in a warming ocean. In this thesis we explore the impact of temperature on these interactions with an integrative method combining laboratory experiments and mathematical modelling. We focus on the pico-eukaryote genus Micromonas. In a first study, we have characterized the temperature response of the Micromonas genus by studying 11 different strains. We have shown the primordial role of temperature on the ecology of phytoplankton. In particular, we have demonstrated that ocean temperature has played a decisive role in evolution. Thus, we have been able to predict the evolution of biodiversity in a warming ocean. In a second study we showed that temperature is a key factor in controlling the phytoplankton - virus dynamics. The temperature affects in particular the rates of infectivity loss and of virus degradation, as well as the rate of virus production. In particular, we observed a change in infection strategy. Beyond a temperature close to the optimal growth temperature, the dynamics become more complex suggesting a change in infection strategy from lytic to chronic. In a third study, we have developed a mathematical model representing these interactions. The model efficiently reproduced the observed changes as a function of temperature. Finally, we discuss the role of temperature on the involved infection processes.
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Submitted on : Friday, December 1, 2017 - 9:07:08 AM
Last modification on : Friday, May 29, 2020 - 4:03:08 PM

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  • HAL Id : tel-01653093, version 1

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David Demory. Impact de la température sur le phytoplancton et ses interactions avec les virus. Océanographie. Université Pierre et Marie Curie - Paris VI, 2017. Français. ⟨NNT : 2017PA066167⟩. ⟨tel-01653093⟩

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