Berkeley Lab Cracks Code on How Corals Survive and Thrive

Scientists just figured out how coral reefs became the rainforests of the sea, and the answer could help save them from extinction.

Researchers at UC Berkeley discovered exactly how tiny algae survive inside coral cells, turning what should be a death trap into a thriving partnership. This relationship transformed corals from simple animals into master reef builders that support a quarter of all ocean life.

The breakthrough happened because assistant professor Phillip Cleves built something remarkable: a saltwater nursery where corals spawn throughout the year. In nature, corals on the Great Barrier Reef release their eggs and sperm just once annually during a full moon in November, making genetic research nearly impossible.

Cleves and his team manipulated light and temperature to trick different coral groups into spawning every few months. This gave them endless opportunities to run experiments that would have taken decades otherwise.

What they found challenges everything scientists thought they knew. The algae aren't peaceful guests invited into special compartments inside coral cells. Instead, they're clever survivors that figured out how to live inside lysosomes, the cellular organs that normally digest and destroy invaders.

"Parasites basically trick cells to do what they want," Cleves explained. "The algae are hijacking the nutrient centers of the cells and acting like food that just never gets digested because they can fix carbon and make glucose from photosynthesis."

The team identified over 200 proteins involved in this relationship, including one that transports bicarbonate to feed the algae carbon dioxide for photosynthesis. Using CRISPR gene editing on lab-grown corals, they proved this transporter is essential for the partnership to work.

The algae pump out glucose to feed the coral. The coral provides shelter and nutrients for the algae. Both thrive together, creating the massive reef structures that protect coastlines and sustain millions of species.

Why This Inspires

This discovery matters beyond understanding an ancient partnership. Warming oceans are causing algae to abandon corals in massive bleaching events, turning vibrant reefs into lifeless skeletons. Understanding exactly how this relationship works at the molecular level gives scientists new targets for intervention.

Cleves is now investigating which proteins break down under heat stress and why the partnership fails. If researchers can identify the weak points, they might find ways to strengthen the bond between algae and coral or help them reunite after bleaching events.

The year-round spawning lab itself represents a revolution in coral research, turning a field limited by nature's schedule into one where breakthroughs can happen continuously.

After 500 million years together, we finally understand how corals and algae became one of nature's most successful teams—and that knowledge might be exactly what we need to keep that partnership alive.