Community shifts in the coral Oculina patagonica holobiont in response to confinement, temperature and vibrio infections

Abstract

Background Extensive research on the diversity and functional roles of the microorganisms associated with reef-building corals has been promoted as a consequence of the rapid global decline of coral reefs attributed to climate change. Several studies have highlighted the importance of coral-associated algae (Symbiodinium) and bacteria and their potential roles in promoting coral host fitness and survival. However, the complex coral holobiont extends beyond these components to encompass other entities such as protists, fungi, and viruses. While each constituent has been individually investigated in corals, a comprehensive understanding of their collective roles is imperative for a holistic comprehension of coral health and resilience.Results A metagenomic analysis was performed to investigate the entire microbiome of the coral Oculina patagonica under various stress conditions, including aquaria confinement, heat stress, and Vibrio infections. Results revealed significant shifts in the abundances and richness of dominant bacterial phyla within the microbiome. In general, aquaria confinement led to an increase in Rhodobacteraceae, Flavobacteraceae, and Vibrionaceae families, accompanied by a decrease in Streptomycetaceae. Concurrently, it was observed that both the abundance and richness of microeukaryotic species significantly declined. Some fungi such as Aspergillus, Fusarium and Rhizofagus genera decrease (or increased, in the case of Saccharomyces). Furthermore, our analysis also identified a reduction in genes associated with antimicrobial compound production by the coral itself, as well as by Symbiodinium and fungi.Conclusion Our findings suggest that the interplay between microeukaryotic and prokaryotic components of the coral holobiont may be disrupted by stress conditions, such as confinement, increase of seawater temperature or Vibrio infection, leading to a dysbiosis in the global microbial community that may increase coral susceptibility to diseases. Further, microeukaryotic community seems to exert influence on the prokaryotic community dynamics, possibly through predation or the production of secondary metabolites with anti-bacterial activity.