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Headline: The healing touch: Scientists discover contact with healthy 'clones' can quickly cure bleached coral
Caption: **VIDEO AVAILABLE: CONTACT INFO@COVERMG.COM TO RECEIVE** BY MARK WORGAN Scientists have discovered a way to heal severely bleached corals- by touching them with healthy clones. Coral bleaching is an increasing worry for researchers, with climate change causing marine heatwaves that threaten to wreck reefs by ‘bleaching’ and killing off the coral. That’s because corals rely on beneficial algae living inside their tissues for energy. When sea temperatures rise, they expel these algae, causing them to turn white in a process known as bleaching. Without their algal partners, corals can become weakened, starve and become more vulnerable to harmful algae. Even when corals survive bleaching, full recovery can take months or years, and some estimates suggest corals could disappear within decades if current trends continue. However, the new study showed corals could recover fully within seven weeks after brief physical contact with the healthy clones. The laboratory study, published on 14 October in Science Advances, found that contact allowed bleached fragments to regain their colour and recover, while bleached corals that did not make contact died. “While bleached corals may be dying, they are not dead yet,” said lead author Danny Collins, a PhD student studying oceans at Stanford University's Doerr School of Sustainability. “The question we wanted to answer is, once a coral has bleached, what can we do?” Corals are animals that can reproduce by producing genetically identical copies, known as clones. These can grow together to form large colonies, often making up extensive reefs. The discovery began in 2025, when study co-author Steve Palumbi, a professor of marine sciences at Stanford, noticed that two coral fragments in his laboratory had fallen against one another in a tank. One fragment was bleached and the other healthy. At the point where they touched, the bleached coral began to regain its colour, indicating that beneficial algae were returning. Around the same time, Collins was investigating how coral diseases develop, including how harmful bacteria carried on plastic debris can infect 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.” To test the idea, the researchers paired 10 sets of coral fragments taken from the same animal. In five pairs, the healthy and bleached fragments were placed in direct contact. The other five pairs were positioned a few millimetres apart. The bleached fragments that touched healthy corals recovered fully within seven weeks. Those kept apart died. “Genetically identical corals recognize one another when they come into contact,” said Palumbi, who is also a professor of biology at Stanford's School of Humanities and Sciences. “Their tissues fuse if they are from the same clone. We see something similar in humans. Organ transplants are often successful if the donor is your identical twin.” Using a powerful microscope, the team found that tiny channels in the coral tissues aligned shortly after contact, creating pathways through which material could pass between the fragments. Beneficial algae and the nutrients they produce moved through these channels. The researchers detected algae passing from healthy to bleached corals within three days. The researchers also investigated how long the corals needed to remain in contact to recover. They separated paired fragments at different intervals and found that a week of contact was enough to provide the bleached corals with sufficient algae to complete their recovery independently. In some cases, just five days of contact was enough. Once separated, the corals still recovered within seven weeks – the same time taken by fragments left in continuous contact. This suggested that the main driver of recovery was not the continued transfer of algae from the healthy coral, but the rapid multiplication of algae already established in the bleached fragment. “Once beneficial algae enter bleached corals, they don’t just spread out,” said Palumbi. “They flood in and start dividing at the fastest rates seen in corals.” During the second week of contact with healthy corals, the algae inside bleached fragments doubled every four days – about 10 times faster than the rate observed in wild corals. Scientists have spent decades developing ways to protect coral reefs from bleaching, disease and ocean acidification. Approaches include selectively breeding heat-tolerant corals, growing corals in nurseries to restore damaged reefs and transplanting coral microbiomes – the communities of microorganisms living in and around corals. The latest findings could offer another route to helping bleached corals recover before they die. “Bleached corals are often considered a lost cause because recovery after a heatwave is very slow, if it happens at all,” said Fiorenza Micheli, a professor of marine science at Stanford and one of Collins's academic advisers. “We hope this new research will inspire solutions that keep corals healthy long enough to enable full recovery after heat waves through slower processes such as growth, reproduction, and recruitment of new colonies.” However, the researchers caution that the technique has limitations. It requires a healthy, genetically identical copy of each bleached coral, making it impractical to apply on the scale needed to restore entire reefs. The team plans to investigate other ways of delivering beneficial algae to bleached corals without requiring direct or prolonged contact. One possibility is to collect algae from healthy corals before marine heatwaves occur and then introduce them in large quantities to bleached corals to accelerate recovery. “These new insights into how corals can naturally recover give us hope for the future,” said Micheli, who also co-directs Stanford's Center for Ocean Solutions. “They open the door to what’s possible and may lead to the breakthrough we need to accelerate reef restoration.”
Keywords: stanford university,photo,video,corals,bleaching,climate change,oceans,nature,science,natural world
PersonInImage: In a laboratory setting, researchers have shown that corals can fully recover from bleaching within seven weeks through brief contact with healthy corals.