Coral reefs are among the most biodiverse ecosystems of the planet but also among the most threatened, currently dying at record rates across the world due to climate change.

Reducing carbon emissions is considered the main way to help them, which would prevent waters from getting too hot and acidic. But researchers in Australia are exploring other alternatives as well, such as training the microalgae that keep corals alive.

Higher average temperatures put stress on coral and can lead to them ejecting their symbiotic algae, a process known as coral bleaching. When that happens, it can be a death sentence for coral and the species that rely on healthy reefs. In an effort to help them, scientists created an exposure therapy experiment for the tiny algae that provide them with life.

“Coral reefs are in decline worldwide,” lead-author Patrick Buerger said in a statement. “Climate change has reduced coral cover, and surviving corals are under increasing pressure as water temperatures rise and the frequency and severity of coral bleaching events increase.”

The researchers exposed ten strains of algae to water heated to about 89 degrees Fahrenheit (or 31ºC) for four years, which is roughly the peak temperature the Great Barrier Reef reached in February. That threshold has been registered to trigger mass bleaching.

Then, the team compared those strains to other algae, which they’d exposed to roughly 81 degrees Fahrenheit (or 27ºC) over the same period. It turns out algae can develop higher heat tolerance. All ten of the strains exposed to higher temperatures evolved to withstand them.

The researchers then introduced those strains to coral larvae and exposed them to water warmed to 89-degree Fahrenheit (or 31ºC) to see if they could also help prevent the coral from bleaching. In three out of the ten cases, the coral didn’t eject the algae. This suggests that algae that have adapted to heat could help restore the world’s coral reefs and buffer them against future change.

“While evidence suggests that corals are slowly adapting to a warmer world, it appears they are struggling to keep pace with climate change,” the researchers said in a statement.

If more research confirms these results and labs are able to develop more heat-resistant algae, scientists could introduce them to coral reefs in the wild. The researchers think this could give reefs a big boost in resisting the effects of the climate crisis.

Despite covering less than 0.1% of the ocean floor, reefs host more than one-quarter of all marine fish species, in addition to many other marine animals. Additionally, reefs provide a wide variety of ecosystem services such as subsistence food, protection from flooding, and sustain the fishing and tourism industries.

The study was published in the journal Science Advances.