Response at the genomic scale of plankton communities to climate change and consequences on their biogeographies

• Main Author: Frémont, Paul
• Other Authors: Génomique métabolique (UMR 8030), Genoscope - Centre national de séquençage Evry (GENOSCOPE), Université Paris-Saclay-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université Paris-Saclay-Direction de Recherche Fondamentale (CEA) (DRF (CEA)), Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université d'Évry-Val-d'Essonne (UEVE)-Centre National de la Recherche Scientifique (CNRS), Université Paris-Saclay, Olivier Jaillon, Marion Gehlen
• Format: Doctoral or Postdoctoral Thesis
• Language: French
• Published: HAL CCSD 2022
• Subjects: Plankton; Environmental omics; Climate change; Tara Oceans; Modeling; Plancton; Omiques environnementales; Changement climatique; Tara Océans; Modélisation; [SDV.EE]Life Sciences [q-bio]/Ecology; environment; Arctic; Arctic Basin; North Atlantic; Phytoplankton
• Online Access: https://theses.hal.science/tel-03967591; https://theses.hal.science/tel-03967591/document; https://theses.hal.science/tel-03967591/file/2022UPASL062.pdf

Microscopic marine plankton are organisms ranging from viruses to small metazoans, bacteria and protists. Plankton is transported passively by the currents, thrives in every oceans and plays a crucial role in the Earth system. Through photosynthesis, phytoplankton drives primary production and the resulting flux of organic matter supports the entire oceanic food web. Plankton also participates in the biological carbon pump, a mechanism by which organic matter sediments to the seabed and is stored there. Today it is essential to assess and project the response of plankton to climate change caused by the burning of fossil fuels. In this thesis, I study this issue through the lens of biogeography, a discipline that focuses on the distribution of organisms in and interacting with their environment through time and space. In a first part, I study the distribution of plankton in the global oceans and its response to climate change using omics data from the Tara Oceans expeditions and climate models. A partitioning of the oceans into genomic provinces depending on the size of the organisms is described. These provinces are related to physico-chemical parameters using machine learning techniques and extrapolated to the whole ocean. A set of "signature genomes" for each province is also highlighted. A major reorganization of the provinces in response to climate change is projected over approximately 50% of the oceans by the end of the century. Important changes in plankton composition would result in a decrease by 4% of the global carbon export flux, which would have an aggravating effect on climate change. In a second part, I study the changes in gene expression of eukaryotic plankton along the transition between the North Atlantic Ocean and the Arctic basin. Among the physical variables, temperature is the variable that best explains transcriptional changes. Functional analysis of genes correlating with the strong temperature gradient reveals a common acclimation strategy of eukaryotic algae. This strategy includes ...