Abstract
In the context of global warming, coral reefs are experiencing thermal stresses which are becoming more frequent and intense. In order to get a better understanding of the mechanisms of coral thermotolerance, I developed an integrative approach on the coral holobiont (meta organism composed of the coral host, its symbiotic algae and microbiota). For this, I performed an ecologically realistic thermal stress experiment on a coral species, Pocillopora damicornis. This species is widespread in the IndoPacific area. I compared the response of two populations whose thermotolerance is different since they are subjected to contrasting thermal regimes. I analyzed, for each of them, the response of the coral host (by RNAseq), as well as the structure and changes in the algal and bacterial microbiota (by metabarcoding). The results show that,while the structure of the microbiota is not influenced by stress, coral responds very differently depending on the population studied. The population from a more fluctuating environment displays a more effective and more plastic response, probably thanks to the involvement of epigenetic mechanisms. Another study carried out on different populations of P. damicornisshowed that the composition of the microbiota is influenced by the host genome and the thermal regime. One of the clades of the symbiotic algae, known to improve the heattolerance of the coral host, appears more sensitive to low temperatures than the others.