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Molecular mechanisms could help coral reefs survive a warming ocean.

On a healthy reef, color dominates. It feels like living in a kaleidoscope – vivid oranges, electric blues, and branching corals teeming with life. But across the Caribbean, that vividness is fading. Today’s divers see an environment that looks like a gravel parking lot scattered with a few lonely coral heads. 

“If you were to dive on any given coral reef in the Caribbean,” says Jake Warner, an assistant professor of marine biology at the University of North Carolina Wilmington, “you would see a few solitary coral heads and a lot of dead coral rubble.”

Research shows that up to 99% of warm-water coral reefs could disappear by 2050, with climate change driving the losses. Warmer oceans trigger coral bleaching, a process in which heat-stressed corals expel the photosynthetic algae living in their tissues, which provide the majority of their nutrition. Bleached corals may not die immediately, but they become vulnerable to disease, mortality, and habitat loss while threatening biodiversity and human coastal livelihoods. 

“A dead reef is not good for anyone,” says Scott Baker Jr., fisheries specialist with North Carolina Sea Grant. “Not for tourism, diving, and certainly not good for the fish and invertebrates that rely on healthy corals as part of their life cycle.”

Healthy reefs are the backbone of a blue economy, supporting about 25% of all marine life and driving billions of dollars in tourism, fisheries, and shoreline protection for coastal states like North Carolina. 

One disease in particular, Stony Coral Tissue Loss Disease, has spread through the Florida Keys in recent years. “Everything is happening at once,” Warner explains. “Temperature, disease, pollution — they’re all interacting.” 

UNCW Center for Marine Science is at the forefront of coral engineering. While most conservation efforts focus on preserving reefs or gardening corals by replanting them, Warner’s approach is to study the animals’ molecular makeup to understand and potentially improve their resilience. 

“Preservation is probably the least likely to happen just based on human nature,” Warner says. “Coral gardening is extremely labor-intensive and a stopgap. If you’re not fixing the underlying problem of the environment, it’s a Sisyphean task.”

Corals are quite difficult research subjects. Most tropical species reproduce once or twice in a year, usually in the middle of the night following a late summer full moon. “In the past, you had to be out on a reef with nets in the dark, often in remote locations without a lab nearby,” Warner explains. 

To address this, the UNCW team built the Spawning and Embryo Analysis System, a series of tanks fitted with lights that mimic seasonal sunlight and moonlight as well as water temperature controls that track Caribbean seasons. 

Corals kept inside these tanks spawn on schedule, releasing their gametes — reproductive cells — into the water there in the lab. “Rather than going to the field with all our equipment, we can actually bring the field to us,” Warner says. 

While corals are often associated with tropical reefs, North Carolina is home to Astrangia poculata, commonly known as the northern star coral. Found along the East Coast, from Florida to Massachusetts, it is a temperate coral that Warner uses as a primary subject in his lab. 

He describes it as “very low maintenance,” because Astrangia poculata can survive a wide range of temperatures, offering a unique way to understand how corals adapt to environmental stress. Its ability to survive year-round in lab conditions makes it valuable for experiments that are difficult with tropical species. 

Warner’s lab collects the eggs and uses CRISPR-Cas9, a gene-editing technology like “molecular scissors” that cut DNA at precise locations. These techniques are still in their early stages in coral gene editing. 

“We’re still at the stage of asking basic questions,” he says. “What makes a coral a coral?”

Past experiments have already shown that disabling certain heat-response genes makes corals less able to survive high temperatures. Other studies have identified genes essential for skeleton formation. Warner’s team focuses on this kind of foundational work.

His lab performs gene knockouts — genetic engineering techniques that delete a specific gene in an organism to make it non-functional — in order to silence a gene called coadhesin. Without it, coral larvae are unable to form their calcium carbonate skeletons. 

Despite its promise, most of this work remains experimental. Scientists are still building the knowledge needed before large-scale applications, such as reef restoration, can be feasible. One of the main challenges to this promise is scalability.

“Coral gene editing is still very low throughput, it’s very expensive, and it would be a tiny drop in an enormous ocean,” Warner says.

“Healthy habitat is the building block of healthy fisheries,” says Baker, “and I don’t feel we should dismiss any opportunity to improve habitat.”

However, from a fisheries perspective, that long shot is worth taking.

“Healthy habitat is the building block of healthy fisheries, and I don’t feel we should dismiss any opportunity to improve habitat, even if that approach is different,” says Baker. “You can’t know if it works if you don’t try.”

The idea of releasing genetically modified corals into the ocean also raises complex ethical and geopolitical questions. Coral larvae can drift for miles on ocean currents and for weeks before settling, crossing national boundaries and potentially colonizing another country’s reef. 

“There’s no geopolitical border in the sea,” says Warner. “What you do in one country could easily end up in another.”

For now, the work remains in the lab, studying embryos, tracking gene activity, refining tools, and building knowledge needed to understand coral biology. But as oceans continue to warm, the question is no longer whether reefs are changing but whether science can keep up.

more on healthy ecosystems

lead photo credit: adobestock.

Emma Davies is an award-winning journalist and a contributing editor for Coastwatch. Her work includes the “Across the Atlantic” series. She recently completed her master’s in liberal studies at NC State University, with a concentration in communication and genetic engineering.