Adaptation of symbiotic coral micro-algae to environmental changes in the Pacific Ocean

• Main Author: Lê-Hoang, Julie
• 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), Global Oceans Systems Ecology & Evolution - Tara Oceans (GOSEE), Université de Perpignan Via Domitia (UPVD)-École Pratique des Hautes Études (EPHE), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Aix Marseille Université (AMU)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université d'Évry-Val-d'Essonne (UEVE)-Université de Toulon (UTLN)-Institut National de la Santé et de la Recherche Médicale (INSERM)-Sorbonne Université (SU)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Université Grenoble Alpes 2016-2019 (UGA 2016-2019 )-Institut de Recherche pour le Développement (IRD France-Nord )-Ecole Normale Supérieure Paris-Saclay (ENS Paris Saclay)-European Molecular Biology Laboratory (EMBL)-École Centrale de Nantes (Nantes Univ - ECN), Nantes Université (Nantes Univ)-Nantes Université (Nantes Univ)-Université australe du Chili, Université Paris-Saclay, Patrick Wincker
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: HAL CCSD 2021
• Subjects: Metatranscriptomic; Tara Pacific; Symbiodiniaceae; Métatranscriptomique; [SDV.EE]Life Sciences [q-bio]/Ecology; environment; Ocean acidification
• Online Access: https://theses.hal.science/tel-03627907; https://theses.hal.science/tel-03627907/document; https://theses.hal.science/tel-03627907/file/2021UPASL091.pdf

Coral reefs are an ecosystem which gather a very large marine biodiversity. The coral is a marine animal living in obligatory symbiosis with a photosynthetic micro-algae of the Symbiodiniaceae family. The Symbiodiniaceae family includes a very high diversity classified in 9 genus. Coral reefs are also a major asset for populations living nearby, thanks to the abundance of fish they shelter. They also have a capital importance for the economy of these regions, in particular through the coast protection and the tourism.Today, coral reefs are threatened by global and local environmental changes that degrade these ecosystems. Among these environmental changes, we find oceanic temperature increases, ocean acidification and local pollutions. These disturbances of the marine environment weaken the obligatory symbiosis between the coral and its micro-algae, which can lead to a symbiotic break (coral bleaching), and then the coral death.In this context, the Tara Pacific expedition proposes to study the coral ecosystem at ocean scale, carrying out a vast sampling plan on 32 islands distributed in the Pacific Ocean. During this expedition (2016-2018), three kinds of corals genera were studied: Pocillopora, Millepora and Porites. In order, to get a global view of these species at ocean scale, metagenomic, metatranscriptomic and metabarcoding high throughput sequencing methods were applied to each coral sample.With Tara Pacific datasets from the first 11 islands, the thesis objectives were to carry out a global transcriptomic study of the photosynthetic micro-algae, using bioinformatic tools, to better understand its diversity and its adaptation at ocean scale. The thesis made it possible to carry out analyses on the expression of the photosynthetic micro-algae in the different coral species sequenced.A specific analysis was carried out on Cladocopium and Durusdinium, which are symbiotic micro-algae of the Pocillopora coral. Population structure of Cladocopium micro-algae was done, followed by differential expression ...