Stanford Researchers Find Healthy Coral Can Revive Bleached Neighbors

Marine ecologists at Stanford University have discovered that bleached corals can rapidly recover when placed in physical contact with healthy coral neighbors. Published in the journal Science Advances, the findings offer a potential new pathway for addressing the widespread degradation of marine ecosystems caused by rising ocean temperatures.

During recent global marine heat waves, a vast majority of the world's coral reefs have suffered from severe bleaching. This occurs when thermal stress kills off the single-celled phytoplankton known as dinoflagellates that live within the coral in a symbiotic relationship. While reefs can sometimes recover naturally by absorbing algae drifting in the surrounding water, the process is typically too slow to prevent widespread mortality.

Researchers at Stanford's Hopkins Marine Station and the Center for Ocean Solutions decided to test whether direct physical contact could accelerate this recovery process. Danny Collins, a PhD student, assembled ten coral test pairs of the Pocillopora damicornis species, pairing one bleached fragment with one healthy fragment. Half of the pairs were allowed to touch, while the others were separated by a few millimeters.

The results showed that bleached corals physically touching a healthy partner recovered fully in just eight weeks. Advanced microscopic imaging revealed that beneficial symbiotic algae and nutrients flooded from the healthy coral into the bleached specimens, dividing at exceptionally fast rates. However, the researchers noted a key limitation: this healing contact currently appears effective only between genetically identical coral specimens that can successfully fuse tissue upon contact.

While scaling the technique presents challenges due to genetic matching requirements, the discovery could complement existing conservation strategies. Researchers hope that combining coral contact with other ongoing restoration efforts, such as cultivating protected coral nurseries and breeding heat-tolerant strains, might help safeguard threatened marine habitats.