The optimal remedy for a struggling coral might be the simple act of touch.
Researchers at Stanford University in California made an intriguing discovery when two coral pieces in their laboratory—a bleached one and a vibrant, healthy one—came into contact after tipping over in a tank.
“We observed the healthy coral transferring these vibrant, beneficial algae to the bleached coral, and we witnessed its color rejuvenate almost instantly,” said ocean scientist Danny Collins during an interview with As It Happens guest host Dave Seglins.
He noted that within a few weeks, the deteriorating coral had improved “to the extent that it was indistinguishable from the healthy coral.”
“We were amazed,” Collins remarked. “This appears to potentially pave the way for reef restoration efforts.”
The research, published this month in the journal Science Advances, offers renewed optimism amidst a crisis where global coral reefs are at significant risk of collapse. However, researchers emphasize that these findings are currently restricted to laboratory conditions, and any attempts to restore coral must coincide with protective measures.
Vibrant coral reef ecosystems are known for their striking colors.
However, Collins explained that this color does not originate from the corals themselves. Instead, it is derived from beneficial algae that are integrated into the coral’s tissues through photosynthesis, supplying essential nutrients.
“The coral provides the habitat, while these algae supply the nourishment. This relationship is crucial for the productivity of coral reef ecosystems,” Collins explained.
This underwater photo taken in the Maldives in 2024 shows hard corals and a bleached branch of coral surrounded by fish. (Sarah Lai/AFP/Getty Images)
“However, as water temperatures rise, both the corals and algae experience stress. Consequently, these beneficial algae begin to emit toxins that are harmful to the coral. In a fascinating response, the coral expels the algae from its tissues.”
This results in corals becoming whitened, malnourished, and close to death, a phenomenon termed coral bleaching.
“We have shown that they are not dead. Furthermore, they possess a remarkable ability to recover swiftly,” Collins stated.
Only effective with genetically similar corals
Despite this encouraging finding, Collins points out that the issue of coral bleaching is far from resolved. The experiments have certain limitations.
For instance, direct contact is essential. When the researchers placed the coral fragments a few millimeters apart, there was no observable effect.
“It may sound like something out of science fiction, but the healthy coral and the bleached coral actually fuse their tissues,” he explained. “This creates a tissue bridge that functions as a nutrient highway, enabling the healthy coral to transfer nutrients and these vibrant algae to the bleached coral.”
Scientists have discovered that when a bleached coral comes into contact with a genetically identical healthy coral, it can recover ‘to the point where it was indistinguishable from the healthy coral,’ according to Stanford University’s Danny Collins. (Danny Collins)
Moreover, this process is only successful with genetically identical corals.
“When we placed them together with different genetic lineages, we observed a fascinating immune and antagonistic response, where the corals rejected one another, similar to how an organ transplant might be rejected by a body,” Collins noted.
He explained that this occurs because corals are “colonial animals”—organisms made up of thousands to millions of polyps.
“When corals of the same genetic lineage touch, they can recognize one another and actually fuse,” he stated.
“Fusion is advantageous in a reef setting because if part of a coral is dislodged during a strong wave, it can reconnect with itself.”
Stanford University ocean scientist Danny Collins states that his latest research offers a potential pathway for coral restoration. (Submitted by Danny Collins)
Approximately 96 percent of the world’s shallow-water reef systems are critically endangered and may vanish by 2075, as reported by the International Union for Conservation of Nature at a UN biodiversity conference in Albania on Thursday.
This could have significant repercussions for biodiversity, tourism, and fisheries, as coral reefs serve as ecosystems that support between 25 to 33 percent of all marine species.
‘Glimmer of hope’
The Stanford study represents a “glimmer of hope” in a landscape filled with concerning news, remarks coral scientist Julia Cole, who was not involved in the research.
“I find it incredibly exciting,” commented Cole, chair of the Department of Earth and Environmental Sciences at the University of Michigan. “The natural world can surprise us in astonishing ways.”
However, she warns that there are challenges ahead.
“Considering the vastness of reefs, which can stretch for kilometers, or in the case of the largest reefs, thousands of kilometers, a process that necessitates coral-to-coral contact would be an extremely detailed and daunting task.”
Collins mentioned that his team is exploring methods to extract algae from healthy reefs, cultivate it in laboratories, and utilize it to safeguard vulnerable reefs from anticipated bleaching events.
“We hope to develop field-deployable and potentially scalable interventions in the near future,” he stated.
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Even if the bleached coral can be rejuvenated, Cole emphasizes that rising ocean temperatures continue to pose a threat.
“We understand how to address the warming climate that is causing these issues,” she stated. “The solution lies in committing to reducing greenhouse gas emissions, phasing out fossil fuels, and transitioning to a clean energy economy.”