How algae help corals bounce back after bleaching 

(Press-News.org) With much of the world’s coral turning a ghostly white, UC Riverside scientists have launched a $1.1 million project to uncover how reefs regain life-giving algae after suffering from heat stress. 

Bleaching occurs when stressed corals lose the algae living in their tissues. Without them, coral turns pale and begins to starve. If algae don’t return within a few weeks, the sickly coral dies, leaving behind a white skeleton that can no longer support the marine life that once depended on it.

“Many corals depend on their algal partners for survival, but we still know very little about how these relationships recover once disrupted,” said project leader and UCR assistant bioengineering professor Tingting Xiang. 

Funded by the National Science Foundation and the Paul G. Allen Family Foundation, the three-year project will use advanced imaging and living experimental systems to learn what’s happening on a cellular level when algae return to bleached reefs. The researchers will use that understanding to drive future restoration strategies that boost this natural process.

One method they will use to study the process involves a type of sea anemone that will act as a stand-in for corals. They’ll stress the anemone, then watch in real-time with high-powered microscopes as colored algae return to the anemone host. 

The team will also use computational modeling, developed in collaboration with UCR assistant math professor Jia Gou, to simulate the algae’s growth once it has returned to a coral host.

“I’m excited to contribute to this project by building computational models that show how algae populations grow inside coral and how that might shape their recovery over time,” Gou said.

Beyond imaging and modeling, the team will also identify the genes and cellular pathways that regulate algae reestablishment. Together, these complementary approaches will shed new light on how coral–algal partnerships rebuild themselves after stress.

Additionally, the project includes an applied component aimed at translating discoveries into practical tools. In collaboration with UCR chemical and environmental engineer Robert Jinkerson, the team is developing a system that could one day help compromised corals recover from bleaching more efficiently.

“One of the most exciting aspects of this project is that we’re not just studying coral recovery in the lab,” Jinkerson said. “We’re working to turn our findings into real solutions that can help restore and save coral reefs.”

Coral reefs make up less than 1% of the ocean floor but support nearly 25% of marine species. They buffer coastlines against storms and sustain economies reliant on tourism and fishing. The United Nations estimates their global economic value at nearly $10 trillion. Yet their decline has been swift: the world lost an estimated 14% of live coral cover between 2009 and 2018. The current bleaching episode is the fourth global event on record—and the most extensive to date.

By learning how corals regain their algae after bleaching and by creating new ways to help this process along, Xiang and her team hope to build both new knowledge and practical tools that can help reefs survive ocean warming.

“Our goal is to advance fundamental knowledge while building new tools that can actively support coral recovery,” Xiang said. “We hope these efforts will help reefs better withstand bleaching events and continue sustaining the ecosystems and communities that rely on them.”


 

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