Bleached corals thrive within days

Researchers demonstrated that bleached coral fragments can be rapidly revived in the laboratory by physical contact with a healthy fragment from the same individual. Working with Pocillopora damicornis, the team paired ten fragments so that each pair contained one bleached and one healthy piece; five pairs were allowed to touch and five were kept separated by a few millimetres. In the touching pairs a tissue bridge formed and photosynthetic algal symbionts (Symbiodiniaceae) migrated into the bleached tissue, with symbiont populations doubling about every four days by week two and full visible recovery achieved within eight weeks. A bleached branch that had touched a healthy partner for a week could continue to recover after separation.

High-powered microscopy showed fusion and symbiont transfer only occurred between fragments from the same genet; fragments from different animals or species did not fuse and separated bleached pieces died by 20 weeks. The finding - observed serendipitously and reported in Science Advances - demonstrates a fast, within-days mechanism for restoring algal populations in bleached coral under controlled conditions and points to a potential, genetically targeted approach for reef-restoration interventions.