As coral reefs struggle to survive in warming oceans, scientists across the world are scrambling to find ways to help these vital ocean ecosystems.
And an interdisciplinary team at the University of Miami discovered a new way to help lab-grown baby corals survive through the often-difficult early life stage.
By growing these tiny baby corals on cement tiles formulated with sodium carbonate, which raises the alkalinity of the water, a research team was able to show that young mountainous star corals are able to survive much better than the average lab-grown corals. And because survivorship among these young corals is often challenging, the technique could prove useful for coral restoration efforts across the globe.
“As a community, we urgently need new approaches for coral restoration, and this is a pilot demonstration that this concept can work,” said Vivek Prakash , assistant professor of physics at the College of Arts and Sciences and a senior author on the study. “We hope this approach can become part of the toolkit for coral restoration, from laboratory settings to natural and hybrid reefs.”
According to their research , published today in Communications Earth & Environment , a Nature portfolio journal, the best-performing tiles increased coral survivorship from about 12 percent—the average survivorship for this species—to 52 percent, representing roughly a fourfold improvement in early-stage coral survival. This was an incredibly significant finding for Chris Langdon , a professor of marine biology and ecology, focused on corals and ocean chemistry, as well as a senior author on the study.
“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. “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, so adding these chemicals in a lab setting dramatically increased the coral’s survival in this early life history stage.”
Led by Melissa Ruszczyk, a former post-doctoral researcher at the University who is now an assistant professor of biology at Keuka College in New York, the interdisciplinary study was co-authored by Prakash and marine biology and ecology professors Langdon and Andrew Baker , along with professors Brian Haus and Peter Swart of the Rosenstiel School of Marine, Atmospheric, and Earth Science , professor Prannoy Suraneni from the College of Engineering , and Margaret Miller, chief science officer at SECORE International , a coral reef conservation organization. Graduate students Skylar Rodriguez, Montale Tuen, Kylee Rux, Veronica Paul, and Maren Stickley also contributed, along with postdoctoral researcher Santhan Chandragiri.
Langdon and Prakash observe coral growth and survivorship in the flumes, designed to replicate the ocean's water flow.
The study began as part of a project led by Baker, Haus, and Miller that was funded by the Defense Advanced Research Projects Agency (DARPA) of the U.S. Department of Defense to explore novel ways to better protect America’s coastlines using coral reefs. However, coral babies begin their life at the size of a pinhead and can take a year or more to grow to the size of a quarter, which is when they are usually planted on reefs.
“We wanted to figure out if we can help baby corals grow more quickly,” said Baker. “The youngest and smallest corals are usually very vulnerable to predators and competitors on the reef, so we wanted to find ways to accelerate their growth so that they could be large enough to avoid these early losses when we put them on the reef.”
Langdon’s two decades of coral research have shown that ocean acidification and warming temperatures are contributing to the demise of coral reefs, and he has discovered that raising the alkalinity of ocean water can help improve coral growth. Therefore, the team decided to increase the alkalinity in the tiles.
They then worked with Suraneni, whose lab specializes in cement substitutes, to create three different chemical formulations for the tiles. The goal was that since the tiles are able to leach some sodium carbonate into the water, it would raise the alkalinity and the pH of the water around the baby corals, changing the surrounding microenvironment and ideally, helping the baby corals to grow. Yet, one of the main effects observed was improved survivorship, Ruszczyk said.
“When we went into this, we did not expect the chemistry of the water to impact survivorship, we thought it would affect growth,” said Ruszczyk. “But arguably, survivorship is an even more important finding if we are trying to use these strategies for coral restoration.”
But the team also wanted to simulate the flow of seawater while the corals were in the lab, to help the fledgling corals grow like they would in the ocean. To do that, Prakash and Ruszczyk used their expertise in fluid dynamics, a branch of physics, to create custom flumes to replicate the ocean flow around corals.
“We wanted to show that if these tiles were deployed on existing reefs, they would experience similar conditions, which could lead to comparable survivorship results,” Prakash said.
Ruszczyk works with other researchers to explain the flume that will hold the baby corals, as part of the study. Photo courtesy of Prakash/University of Miami.
For five months, the team tested cement tiles with no carbonate, with 1 percent of sodium carbonate, and with 2 percent of sodium carbonate. The team also used tiles that had texture on them, and others that were flat, as well as tiles with divots for the baby corals to settle.
Ultimately, the flat tiles with the highest level of sodium carbonate (2 percent) worked best to help the baby corals survive. Now, the researchers are hoping to scale up the work and try this approach with other coral species. Langdon’s lab has already started placing sodium carbonate in the tank water of lab-grown corals and is seeing major improvements in growth rates with the new chemistry.
Suraneni added that the team is now looking into whether different tile shapes and textures can affect coral embryo settlement, survivorship, and growth, including in the field.
Miller, who works on scientific solutions to restore corals globally at SECORE, said that star corals are typically difficult to grow in the lab, so the results are very encouraging.
“The species used in this study is an important one for reef-building, but generally difficult to culture,” she said. “Thus, the improved survivorship shown in this study suggests a restoration tool that could improve outcomes for restoring reef-building coral populations.”
She added that using these refined tiles, which are relatively easy to make, could help improve the viability of coral larvae and prove very useful for those in her field.
“The possibility that tweaking the material composition of such substrates that are already in use is an exciting prospect in improving yields of cultured corals,” Miller said.
Communications Earth & Environment
Experimental study
Animals
"Alkalinity-enhanced artificial substrates modulate local pH and increase survivorship of early-stage coral recruits"
20-Apr-2026
n/a