On a typical day in Chris Langdon's Ocean Acidification Coral Laboratory at the University of Miami, researchers study the quiet, painstaking work of keeping coral alive. It's slow, careful work—but recently, the team made a discovery that could change the trajectory of coral recovery worldwide. By growing baby corals on specially formulated cement tiles that raise the alkalinity of surrounding water, they boosted the survival rate of young mountainous star corals from roughly 12 percent—the species' typical lab survival rate—to 52 percent. That's a fourfold improvement in just five months.
The findings, published in Communications Earth & Environment, represent what the researchers describe as a breakthrough at one of the most fragile moments in a coral's life. "One of the bottlenecks in coral restoration, and why coral reefs aren't recovering on their own today, is that corals are spawning in nature and are releasing eggs into water, but most aren't surviving," said Langdon, a professor of marine biology and ecology. "We can't find many babies recruiting to natural coral reef habitats. We know they are spawning, but not surviving at this very early stage."
The research grew from a larger project led by Andrew Baker, Brian Haus, and Margaret Miller to explore novel ways to better protect America's coastlines using coral reefs. The challenge, Baker explained, is that coral babies begin life the size of a pinhead and can take a year or more to grow large enough to plant on natural reefs. During that time, they're vulnerable to predators and competitors. "We wanted to figure out if we could help baby corals grow more quickly," Baker said. "The youngest and smallest corals are usually very vulnerable, so we wanted to find ways to accelerate their growth so that they could be large enough to avoid these early losses."
The solution emerged from an unlikely collaboration between coral biologists and materials scientists. Langdon had spent two decades studying how ocean acidification and warming temperatures contribute to coral decline—and had found that raising alkalinity can improve coral growth. Working with Prannoy Suraneni's lab, which specializes in cement substitutes, the team created tiles infused with sodium carbonate. The compound leached slowly into the water, raising alkalinity around the young corals just enough to help them thrive.
The study was led by Melissa Ruszczyk, a former post-doctoral researcher now at Keuka College in New York, and co-authored by an interdisciplinary team including Vivek Prakash, assistant professor of physics, who served as a senior author. "As a community, we urgently need new approaches for coral restoration, and this is a pilot demonstration that this concept can work," Prakash said. "We hope this approach can become part of the toolkit for coral restoration, from laboratory settings to natural and hybrid reefs."
With ocean temperatures rising and coral reefs facing unprecedented pressure, the technique offers a glimmer of real promise—not a silver bullet, but a new tool in a growing restoration arsenal. The team is now exploring how these alkaline tiles might be adapted for use beyond the lab, potentially integrating them into natural and hybrid reef systems where baby corals need every advantage they can get.