This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: For the first time, scientists have observed bleached corals on the brink of death fully recover through brief contact with healthy clones. Ghostly white corals returned to full health in a laboratory setting within seven weeks, the fastest documented recovery to date, according to a study published in Science Advances.
The findings could inspire the development of new methods to rapidly restore corals, which, by some estimates, could disappear within a few decades as climate change drives more frequent and intense marine heat waves. When waters warm, corals expel colorful, beneficial algae that live in their tissues and provide the energy that corals need to grow. The loss of their algae partners leaves corals pale, starving and vulnerable to the invasion of harmful algae.
If corals survive these bleaching events, it can take months to years for them to fully recover. "While bleached corals may be dying, they are not dead yet," said lead author Danny Collins, an oceans Ph.D. student at the Stanford Doerr School of Sustainability. "The question we wanted to answer is, once a coral has bleached, what can we do?" All corals are animals.
Across most species, individual corals multiply by producing clones that grow together to form vast, reef-building colonies of the same genetic makeup. In 2025, study co-author Steve Palumbi, the Jane and Marshall Steel, Jr. Professor in Marine Sciences, observed something curious about coral biology in his research lab.
Two coral fragments—one bleached, one healthy—sampled from the same colony had tipped over in a tank and were now touching. Where they made contact, color returned to the bleached fragment, signaling the return of beneficial algae. Around the time of this observation, Collins was considering the origins of coral disease, particularly the transmission of bacteria lurking on plastic debris that settles onto corals.
"Harmful bacteria enter corals through physical contact," said Collins, who is also a Knight-Hennessy Scholar. "We were curious about what would happen if we used contact to reintroduce something good—the beneficial algae from healthy corals." Collins set up a simple experiment. He assembled 10 pairs of coral fragments—one bleached, one healthy—from the same animal.
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