In-situ inoculation of coral probiotics on Acropora sp. and Pocillopora verrucosa shows positive effects on host physiological parameters and the coral-zooxanthellae symbiosis under different environmental conditions

The current climate crisis is threatening coral reefs and the ecosystems they support. In turn biodiversity losses and unpredictable impacts on people's livelihoods who depend on these ecosystems are at imminent risk. The microbiome is an invaluable aspect of the health of corals, fulfilling important physiological functions that promote the well-being of the host. In turn, coral probiotics could become a valuable asset in supporting the health of coral reefs by enriching the microbiome in Beneficial Microorganisms for Corals (BMCs). A project in the Red Sea applied two types of BMCs to colonies of Acropora sp. and Pocillopora verrucosa in-situ over six months, spanning important seasonal variations. The effects of probiotic-treatments were investigated with respect to various physiological parameters (photosynthetic efficiency, zooxanthellae density, pigment content and protein content), all important indicators of coral health. The results indicate that the probiotics had positive effects on the photosynthetic efficiency and density of zooxanthellae in the treated coral colonies. These findings suggest that coral probiotics can have beneficial effects on coral physiological parameters in field conditions.