Abstract. Coral holobionts, the keystone architects of the coral reef ecosystem, comprise notorious associations between an invertebrate host and both eukaryotic and prokaryotic microbes. These provide crucial services to the coral host, covering its nutritional and immunity needs, and therefore contributing to its ecological dominance in tropical shallow oligotrophic waters. Here, I will focus on several case studies to illustrate the degree of integration and interdependence established between corals and their symbionts. At the interface between the host epithelium and the seawater environment, coral surface mucus supports a microbial community that acts as barrier against a wide range of pathogens. Findings suggest a selective role of mucus carbohydrate fractionation in the response of the associated prokaryotic community. I will also show that the fate of the coral holobiont upon external disturbance relates to the degree of disruption of its mucus microbial community, with recovery being dependent on the persistence of an intact beneficial microbiome. I will also explore the biochemical variation and the dynamic response of microbial communities inhabiting the gastrovascular cavity of corals upon feeding activities of the host to elucidate on the fairly unexplored microbial ecology of this semi-closed environment. At last, I will touch on a few examples of particular adaptations of the coral microbiome to the mesophotic reef environment. By jointly presenting this series of recent findings originating from different compartments of the coral holobiont, I highlight the complex but deterministic nature of interactions established between corals and their microbial symbionts.

Biography. Pedro Frade is a postdoctoral researcher at the Centre of Marine Sciences (CCMAR) at the University of Algarve (Portugal). His research focuses on the microbial ecology of coral reef ecosystems, in particular the functional roles played by coral-associated microbial communities belonging to the three domains of Life in the niche diversification and adaptation of their coral hosts. Pedro uses field and laboratorial approaches based on molecular biology and biogeochemistry to investigate the microbiome’s functional diversity in auto- vs heterotrophic corals, across shallow vs mesophotic reefs, and for tropical vs temperate coral hosts. He completed a PhD at the University of Amsterdam in the Netherlands and conducts most of his field research based at the fieldstation of CARMABI Foundation on the South Caribbean island of Curaçao.