Probiotic treatments revive heat-stressed coral in open ocean for the first time

For the first time, researchers have demonstrated that probiotic and postbiotic treatments can revive heat-stressed coral in open ocean conditions, a finding that could reshape how scientists fight to preserve the world's imperiled reef ecosystems. The study, published September 3 in the journal Cell Reports, marks a leap from laboratory success to real-world application for microbial therapies aimed at corals.miragenews+2

Bacteria From Healthy Corals as Medicine

A team led by Erika Santoro, a postdoctoral fellow at the King Abdullah University of Science and Technology (KAUST) in Saudi Arabia, treated colonies of Acropora cf. valida coral in the central Red Sea during a natural heatwave in the summer of 2022. Over the 15-day field experiment, daily average seawater temperatures ranged from 30.9°C to 31.9°C.ecomagazine+2

The researchers isolated beneficial bacterial strains from healthy Red Sea corals and developed two probiotic formulations — composed of live microbes — along with two postbiotic counterparts made from inactivated microbes and their bioactive components. After 15 days, one probiotic and one postbiotic formula had improved coral health, as measured by color recovery and the photosynthetic efficiency of the algae living inside the corals.oceanographicmagazine+2

"When an innovative idea like this actually works — particularly under field conditions — we are positively surprised," Santoro said. "The most exciting takeaway is that this study opens a new avenue for coral microbial therapies."ecomagazine

Postbiotics Open the Door to Scaling

The finding that postbiotics — inactivated versions of the live bacteria — also worked is especially promising for practical deployment. "Inactivated microbial formulations could potentially offer practical advantages, such as longer shelf life, easier storage and transportation, and reduced production costs," Santoro said. Genetic and metabolic tests revealed that the two types of treatment restructured coral microbiomes in distinct ways, with postbiotic-treated corals showing an increase in Cobetia, a bacterium associated with heat tolerance.talker+2

A Tool, Not a Cure

The research was conducted at the Coral Probiotics Village at Al Fahal Reef in the Red Sea, a site associated with KAUST's broader coral conservation work. While the results are encouraging, Santoro emphasized that microbial therapies are supplementary tools, not substitutes for addressing climate change. "We see approaches such as probiotics and postbiotics as additional tools that could help improve coral resilience and support restoration efforts, while broader actions address the causes of climate change," she said.eurekalert+2