Singaporean scientists are exploring innovative methods to help local coral reefs withstand rising sea temperatures driven by climate change and an anticipated intensification of the El Niño phenomenon. The research focuses on enhancing coral resilience through the introduction of beneficial bacteria and a controlled heat-conditioning process.

In late May, 160 coral fragments were transplanted to artificial reefs near Kusu Island and St John’s Island. These fragments, small portions of living coral capable of growing into new colonies, will be monitored over a year to assess their growth, survival, coloration, and photosynthetic efficiency. Researchers will also track shifts in the corals’ microbial communities to better understand how these interventions affect coral health.

The project is being conducted under the National Parks Board’s Marine Climate Change Science Programme and involves collaboration between the National University of Singapore’s Lee Kong Chian Natural History Museum and Nanyang Technological University’s School of Biological Sciences. Associate Professor Huang Danwei, deputy head of the Natural History Museum, noted that the transplanted corals will face peak water temperatures from May through July, coinciding with expected marine heatwaves attributed to El Niño.

One approach involves treating coral fragments with a bacterium from the Roseobacteraceae family, identified as a probiotic that enhances heat tolerance. The bacterium was isolated from the ringed plate coral, a species chosen for its relative resistance to bleaching and strong recovery potential following thermal stress. Through DNA mapping and laboratory testing, researchers found that this microbe confers heat resilience through several mechanisms: producing sulfur-derived gases that may contribute to atmospheric cooling, synthesizing vitamins that stabilize heat-sensitive biological processes, and generating antibiotics that protect corals from viral infections.

Coral fragments were immersed in a dilute bacterial solution to allow the microbes to colonize their mucus layers and cells before transplantation. Forty of the transplanted fragments received this probiotic treatment.

Concurrently, another set of coral fragments underwent a heat-conditioning protocol at the St John’s Island National Marine Laboratory. This “heat HIIT” (high-intensity interval training) exposes corals to fluctuating temperatures between 29°C, Singapore’s average sea temperature, and 32°C over a four-week period. This regimen aims to induce thermal tolerance by delivering an accumulated heat load stressful enough to trigger adaptation but not to cause mortality. The treatment notably improved heat resilience, particularly among more vulnerable coral fragments.

Of the transplanted corals, 40 were heat-acclimated, 40 received both probiotic and heat-conditioning treatments, and 40 remained untreated to serve as controls. Researchers seek to determine the optimal combination of interventions to bolster coral survival amid warming seas. A key outstanding question is the duration of the protective effects conferred by the bacterium and heat conditioning.

In addition to the ringed plate coral, three other species, including a cauliflower-shaped coral, are undergoing similar trials in controlled aquaria. These corals are slated for transplantation in 2027, as part of ongoing efforts to safeguard Singapore’s reefs against the adverse impacts of climate change.