Invisible engineers: Predicting reef futures by determining microbiome structure at competitive interaction zones

The interfaces between coral and algal holobionts represent the battle front of fierce competition for space on the reef. Growth of one holobiont over another at these interaction interfaces determines the benthic community structure on reefs. Coral-algal interaction zones frequently promote higher microbial respiration rates. This enhanced microbial activity and concomitant depletion of oxygen at interfaces creates a microenvironment that often reaches hypoxic levels known to harm corals. This microbial-mediated oxygen depletion provides a competitive advantage to benthic algae at interaction zones. The organic exudates released by fleshy macroalgae have also been shown to select for potential coral pathogens; further implicating microbial processes in algal competition over coral holobionts. Resolving the connection between coral microbiome structure and distinct algal competitors is critical for effective management and restoration of coral reef systems.