PhD student: Corentin HOCHART

Supevisor (ASR): Pierre Galand

General information:
Often called "the rainforests of the sea", tropical coral reefs are one of the most biologically diverse ecosystems on the planet, supporting up to 25% of all marine fish in less than 0.1% of the world's ocean area. Coral reefs harbor complex microbial communities composed of protists, algae, fungi, bacteria, archaea, and viruses. However, most of this diversity has yet to be described. These microorganisms are fundamental drivers of biogeochemical cycling and contribute significantly to host health and ecosystem homeostasis. This association has allowed coral reefs to colonize many different habitats in oceanic waters with low amounts of nutrients and form massive reef structures. However, threatened by pollution and climate change, coral reefs are rapidly shrinking. Gaining a better understanding of the coral reef microbiome is necessary to understand the threats it faces. Previous studies suggest that both host and environmental factors shape the composition of the microbiome. In particular, coral microbial communities appear to be host species-specific despite seasonal environmental variations or geographic distribution. The structure of the microbiome also largely differs from the microbes in the water column. Another recent finding is that a phylosymbiosis exists between corals and microbes.

Although coral-algae symbiosis is well characterized, less is known about coral-prokaryotic interactions. Elucidating these interactions is complicated by several factors: (i) the high diversity of the microbiome, (ii) the small fraction of culturable organisms, and (iii) the lack of information on microbial functions or metabolisms. Thus, the microbial functions associated with the symbiosis and evolution of these microbial communities are still underexplored.

The goals of my thesis are to (i) characterise the function of tropical coral reefs’ microbiomes and (ii) describe patterns of bacterial population genetics with the aim of identifying the ecological and evolutionary factors that shape the host-microbe relationship.

Coral reefs’ microbial communities will be investigated through comparative whole genome sequencing and 16-based metagenomics plus genomics with a focus on both coral and crustose coralline algae (CCA) of different islands in Pacific Ocean.