BY THE OPTIMIST DAILY EDITORIAL TEAM
Two coral fragments fell over in a Stanford lab tank. When they touched, one healed the other.
The bleached fragment, starved of the symbiotic algae that give coral both its color and its nutrition, began recovering within days. “We watched the healthy coral send over these colourful beneficial algae over to the bleached corals, and we watched its colour restore basically in front of our eyes,” said ocean scientist Danny Collins. Within a couple of weeks, the dying coral had recovered to the point where it was indistinguishable from its healthy neighbor. “We were blown away,” Collins said. “It does seem like this could open a door to possible reef restoration.”
The findings, published last month in Science Advances, suggest that bleached coral is not necessarily dead, and that it can recover faster than researchers expected.
The magic of the tissue bridge
The recovery requires direct physical contact and a genetic match. When Collins’s team separated the fragments by a few millimeters, nothing happened. When they introduced corals from different genetic backgrounds, the corals rejected each other the way a body might reject a donated organ.
When genetic clones made contact, their tissues fused. “They create a tissue bridge that kind of acts as a nutrient highway that allows for the healthy coral to then send over nutrients and this colourful algae over to the bleached coral,” Collins said.
Coral is a colonial animal, a single organism made of thousands to millions of individual polyps. Fragments of the same genetic background recognize each other on contact and merge rather than fight. Collins noted this serves a natural function. If a piece breaks off in a wave, it can reconnect with the original colony.
96 percent of reefs are at risk
The International Union for Conservation of Nature announced that about 96 percent of the world’s shallow-water reef systems are critically endangered and could disappear by 2075. Coral reefs support between a quarter and a third of all marine species, along with fisheries and coastal economies that hundreds of millions of people depend on.
Coral scientist Julia Cole, who was not involved in the study, called the Stanford findings “a glimmer of light.” Cole chairs the Department of Earth and Environmental Sciences at the University of Michigan. She was enthusiastic but clear-eyed about scale. “If you think about the scale of reefs as kilometers, or in the case of the biggest reefs, thousands of kilometers … something that requires coral-to-coral contact, it would be a very meticulous and kind of overwhelming project,” she said.
Collins’s team is working on extracting algae from healthy reefs, culturing it in labs, and deploying it to protect at-risk reefs ahead of expected bleaching events. “We hope in the near future we can have some interventions that actually could be field deployable and possibly scalable,” he said.
The restoration work doesn’t address what’s warming the ocean in the first place. “We know how to solve the warming climate that’s causing these problems,” Cole said. “It comes back to getting serious about reducing greenhouse gas emissions, getting off of fossil fuels and transitioning to a clean-energy economy.”
Source study: Science Advances – Rapid coral bleaching recovery via symbiont transfer from healthy corals
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