Environmentalists are celebrating a breakthrough made by scientists at Stanford University that could help to boost coral reef populations. Here is a look at the findings and what it could mean for parts of the world’s oceans adapting to climate change.

Scientists Unlock Surprising Coral Recovery Finding

Bleached corals are one of the most devastating side effects of climate change. However, for the first time in history, scientists have found that exposing these bleached corals to healthy clones could restore their health.

The details of this study were published in Science Advances on October 14. The authors note that the previously white corals were able to return to full health within seven weeks in this laboratory setting, marking the quickest recovery to date.

These findings could signal new methods to restore these dying corals that are increasingly becoming victims of marine heat waves linked to global warming. The once colorful coral expels the beneficial algae within its tissues as ocean waters become warmer.

This algae is what provides the coral the energy that it needs to thrive. The end result is starving coral that turns into ghostly white coral. Any coral that is able to survive these mass bleaching events typically takes years to recover.

According to the study’s lead author Danny Collins, an ocean PhD student at the Stanford Doerr School of Sustainability, “While bleached corals may be dying, they are not dead yet.”

Details of What the Scientists Observed

Scientists note that coral is technically an animal that multiplies by producing clones that form the vast network of reef-building colonies in the world’s oceans. Study coauthor Steve Palumbi, the Jane and Marshall Steel, Jr. Professor in Marine Sciences, observed that one bleached coral fragment was touching another healthy coral in his research lab. When these two different corals made direct contact, color began to return to the bleached portion. This signaled that the beneficial algae were starting to return to the damaged coral.

This observation was useful to Collins as he was working to understand the origins of coral disease. Collins said that “harmful bacteria enter corals through physical contact. We were curious about what would happen if we used contact to reintroduce something good – the beneficial algae from healthy corals.”

The findings inspired Collins to set up an experiment with different degrees of healthy and bleached coral fragments from the same animal. Collins set five pairs close enough to touch, while leaving gaps of a few millimeters between the rest of the subjects. What he found was that the bleached coral recovered fully within seven weeks. The fragments that were not touching the healthy coral died.

“Genetically identical corals recognize one another when they come into contact,” said Palumbi. The scientist also explained that “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.”

The team of scientists used a powerful microscope to learn that the tiny channels within a coral structure align shortly after contact. This alignment creates a path between the two corals, sending the beneficial algae and its associated nutrients from the healthy coral to the diseased coral.

The scientists observed that it took only three days for this transport to happen. They also found that it generally took just one week of contact after receiving the beneficial algae for the diseased coral to be able to complete its recovery on its own.

Once separated, it took approximately seven weeks for the recovery to be complete. This matched the recovery time of pairs that were not separated, leading the scientists to hypothesize that replication of the algae was happening within the diseased animal.

As Palumbi explains, “Once beneficial algae enter bleached corals, they don’t just spread out. They flood in and start dividing at the fastest rates seen in corals.”

Algae within the bleached pieces of coral doubled every four days during the second week of contact. This equates to about ten times faster than the rate measured in corals in the wild.

Why This Discovery Is Significant

Environmentalists have been searching for ways to protect diseased coral for decades. More recently, the focus has shifted to preventative measures, such as selectively breeding coral that tolerates heat better or building coral nurseries designed to replenish degraded reefs.

Up until now, fixing bleached corals had been considered not worth the effort due to the slow recovery time. Scientists now hope that this latest body of research will deliver new ways to promote better coral health.

The Stanford team said that despite the optimism surrounding the study results, there are still many questions that need to be answered. For instance, this approach relies on a genetically identical copy of the bleached coral. This is not feasible for coral in the wild.

What is next? The team said that they plan to explore other ways of delivering healthy algae to coral in need through methods that do not require continuous contact. The goal is to apply these lessons to find alternative ways to speed recovery in bleached coral.

Fiorenza Micheli, the David and Lucile Packard Professor in Marine Science and a faculty advisor of Collins, said that “these new insights into how corals can naturally recover give us hope for the future. They open the door to what’s possible and may lead to the breakthrough we need to accelerate reef restoration.”

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