A Stanford-led laboratory study found that brief contact with healthy coral fragments can seed bleached genetic counterparts with algae and trigger recovery within seven weeks, though the method has not been tested on reefs.
Coral bleaching occurs when stress, often from warm water, causes corals to lose the microscopic algae that provide much of their food and color. Researchers paired bleached and healthy fragments of cauliflower coral, including matching fragments from the same genetic colony, and compared pieces kept touching with pairs held slightly apart. The team found that touching coral tissue fused, creating a route for symbiotic algae to move from the healthy fragment into the bleached one.
In the main experiment, fragments that touched recovered, while those separated by a small gap did not and eventually died or were overgrown. Follow-up tests indicated that about a week of contact—and in some cases just three days—could provide enough algae to start sustained recovery. The approach has important limits: recovery depended on a genetic match, and pairings from different genetic backgrounds could provoke antagonistic responses.
The findings point to a possible restoration tool, but whether it can work at reef scale remains unknown; the study tested small fragments in controlled laboratory conditions, not whole reefs.