Abstract Summary
A major priority in coral restoration is to increase settlement and post-settlement survival by orders of magnitude. Bacteria have the ability to induce settlement in marine larvae, moderate host-symbiont relationships, prevent invasion by pathogens, and improve gut health. To identify, isolate, and apply beneficial bacteria in coral restoration, I conducted CCA choice experiments with larvae from seven Caribbean coral species including the threatened species Orbicella faveolata and Acropora palmata, then isolated hundreds of pure cultures of bacteria from preferred fragments of CCA. Biofilms of these isolates were screened for settlement induction in replicated experiments over a six-year period. Settlement-inducing isolates were tested during multiple spawning cycles and multiple years to ensure reproducibility of effects. Isolates were preserved between spawning seasons as glycerol stocks at -20C and -80C. Isolates that significantly increased larval settlement included strains of Bacillus, Tateyamaria, and Salinimicrobium. A subset of isolates inhibited the growth of coral pathogens such as Photobacterium. Individual and paired settlement-inducing isolates were then applied as cell suspensions in settlement experiments, where they increased both settlement in the lab and survivorship in the water, yielding up to 14 times more surviving settlers overall. Compared to driving the evolution of the animals themselves, beneficial bacteria represent a faster, safer, and reversible tool to boost the physiological performance of coral hosts, including during the critical transition from larva to recruit. Beneficial bacteria can safely and significantly improve outcomes in coral restoration as they already do in aquaculture and medicine. Recognizing this potential, the BMMO Network has been established to communicate methods and best practices among researchers studying Beneficial Microorganisms for Marine Organisms.
