Probiotics reshape the coral microbiome in situ without affecting the surrounding environment

Abstract

Abstract Beneficial Microorganisms for Corals (BMCs), or probiotics, enhance coral resilience against stressors in laboratory trials, being the only sustainable treatment currently explored to retain threatened native corals. However, the ability of probiotics to restructure the coral microbiome in situ is yet to be determined. To elucidate this, we inoculated BMCs on Pocillopora verrucosa colonies in situ in the Red Sea for three months. BMCs significantly influenced the coral microbiome, while those of the surrounding seawater and sediment appeared unchanged. The inoculated genera Halomonas and Pseudoalteromonas were significantly enriched in probiotic-treated corals. Furthermore, probiotic treatment correlated with an increase in beneficial groups (e.g., Ruegeria and Limosilactobacillus), while potential coral pathogens, like Vibrio, decreased in abundance. Notably, treated and non-treated corals remained healthy throughout the experiment. Our data indicate the feasibility of using probiotics in real-world conservation efforts through beneficial restructuring of the coral microbiome without off-target changes in the surrounding environment.