Predicting the response of the oceanic carbon cycle to climate change : eco-evolutionary modeling of the microbial loop and the role of viruses

• Main Author: Cherabier, Philippe
• Other Authors: Institut de biologie de l'ENS Paris (IBENS), Département de Biologie - ENS Paris, École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-École normale supérieure - Paris (ENS-PSL), Université Paris Sciences et Lettres (PSL)-Université Paris Sciences et Lettres (PSL)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Centre National de la Recherche Scientifique (CNRS), Sorbonne Université, Régis Ferrière
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2022
• Subjects: Microbial loop; Eco-evolutionnary processes; Natural selection; Adaptive dynamics; Oceans; Climate change; Boucle microbienne; Processus éco-évolutifs; Sélection naturelle; Dynamique adaptative; Océans; Changement climatique; [SDV.EE]Life Sciences [q-bio]/Ecology; environment; [SDE.MCG]Environmental Sciences/Global Changes; [SDV.EE.IEO]Life Sciences [q-bio]/Ecology; environment/Symbiosis; Ocean acidification
• Online Access: https://theses.hal.science/tel-03828259; https://theses.hal.science/tel-03828259/document; https://theses.hal.science/tel-03828259/file/CHERABIER_Philippe_2022_v2.pdf

Human activities are affecting ocean health dramatically. Climate change caused by anthropogenic greenhouse gas emission results in sea-surface warming, polar ice caps melting, ocean acidification, and changes in circulation and mixing regimes leading to stratification. All life forms in the ocean are impacted, primarily microorganisms which dominate ocean biodiversity and play a major role in global ecosystem function. Microbial communities have a capacity for rapid adaptation because of their large population sizes and short generation times, potentially altering the global cycles of carbon and nutrients in response to climate change, but these feedbacks are largely unresolved. In this thesis, we focus on heterotrophic bacteria and their ability to remineralize dissolved organic matter into inorganic nutrients. This `microbial loop' fuels a carbon recycling pathway, but its response to climate change is still poorly understood. Through eco-evolutionary modeling, we resolve the potential feedback loop resulting from bacterial adaptation in different oceanic regions, both at the surface and deep in the water column. We find that bacterial adaptation tends to mitigate the negative effect climate change has on dissolved organic matter regeneration, with varying degrees depending on the biogeographical region. In order to generate predictions of our model at the global scale, we develop a novel framework for integrating eco-evolutionary processes with Earth system models. We find that bacterial adaptation in the microbial loop adds uncertainty to global ocean ecosystem forecasts, and call for further eco-evolutionary studies at this scale. Finally, we extend our eco-evolutionary modeling framework to address the effect of bacteriophages – arguably a major demographic factor of bacterial populations. We present preliminary analyses of bacteriophages’ influence on the carbon cycle and how they may alter the speed and dynamics of bacterial adaptation to changing environments. Overall, this thesis emphasizes two ...