Coral surface microlayer: dynamics of microbial communities

Microbial biofilms that flourish within mucous sheets play decisive roles on the microspatial to the ecosystem scale. Coral surface mucus forms a dynamic boundary layer between the coral host epithelium and the surrounding seawater. Coral mucus sustains a diverse microbial assemblage and acts as a first barrier of defence against a wide range of environmental disturbances, thereby contributing to the health of the coral holobiont. Surprisingly, only little is known about the physical and chemical properties of this mucus layer, its dynamics of production and maintenance. Particularly, the relation between mucus layer dynamics and the diversity, abundance and function of its resident and visitor microbes remains largely enigmatic. The main goal of this project is to understand the dynamics of composition, secretion and release of coral surface mucus and the related changes on the development, structure and potential function of its associated microbial community. We will apply a multidisciplinary approach that combines measurements of thickness, organic matter, carbohydrate and lipid composition of coral mucus, with molecular phylogenetic analysis, metagenomic profiling and quantification of major domains of the coral mucus microbiome. Overall, the proposed project will elucidate on key topics such as host and microbial specificity, microbial niche diversification, mucus selectivity, microbial succession and the role of microbes on biogeochemical cycles in corals and in the coral reef ecosystem. Further meta-analyses integrating environmental and molecular data will advance our knowledge on coral mucus dynamics from both top-down and bottom-up perspectives. Such study on the dynamics of coral surface mucus layer and its associated microbial communities can contribute to understand and predict impacts on coral reefs arising from environmental stress such as the ones associated with a changing climate. Moreover, the coral mucus biofilm can prove useful as a model to comprehend the dynamics of other microbial (defence) systems that thrive on mucous coatings. The study will most likely also provide information on new genes, pathways and adaptations present within the coral microbial realm.