Coral Nursery Launches to Restore Brain Corals in Butler Bay

In a small mobile laboratory at an eco-hotel on the west end of St. Croix, the miracle of life is taking place. In a petri dish, under a UV light, a fluorescent speck wriggles around in a tablespoon of seawater.  It is the larval form of a grooved brain coral, born just a few days ago, and already it has its sea legs.

Gametes, or packets of egg and sperm, are large and clearly visible in the grooves of the DLAB coral parent colony. (Photo courtesy of Thriving Islands, LLC)

“It’s looking for a place that looks good and smells good, trying to figure out where to settle,” says Dr. Ashlee Lillis, an expert in ecology and lifecycle of this species, Diplora labyrinthiformis (DLAB). Its bright colors and unique shape are iconic to territorial reefs.

Lillis moves the UV light to a nearby plastic tub, revealing hundreds more glowing larvae that have settled onto cement tiles. One has already formed into a coral polyp, complete with microscopic tentacles extended, searching for food. Lillis has affectionately nicknamed this one “Stevie.”

A microscopic view of “Stevie,” one of the first polyps of Diplora labyrinthiformis, or grooved brain coral, to emerge from the coral spawning work of the Butler Bay Coral Restoration Project. (Photo courtesy of Thriving Islands, LLC)

“We released 1.2 million fertilized embryos into the sea a few days ago. We can’t raise that many ‘Stevies’ here,” Lillis says, gesturing to the two folding tables stacked with more settlement bins in the lab. “But we gave those corals a great head start in life.”

Microscopic DLAB polyps fluoresce under UV light in Butler Bay. Their tentacles are extended, searching for food. (Photo courtesy of Thriving Islands, LLC)

Lillis brought her mobile coral spawning laboratory to the Feather Leaf Inn on the west end of St. Croix as part of a pilot project to re-establish DLAB populations in Butler Bay. DLAB corals and other “reef-building” species are in serious decline across the territory due to climate change, coastal development, overfishing, and the latest impact: Stony Coral Tissue Loss Disease. Because these corals support fisheries, tourism, and shoreline protection, the territory has stepped up efforts to conserve and enhance reefs through coral restoration, including recently establishing Butler Bay as a priority site for restoration.

Divers from the Butler Bay Coral Restoration Project collect spawn from grooved brain corals (Diplora labyrinthiformis or DLAB) to create fertilized embryos in a mobile “pop-up” laboratory at Feather Leaf Inn on the West End of St. Croix. The project aims to add as many as 300 new brain corals to the reef in Butler Bay after one year. (Photo courtesy of Thriving Islands, LLC)

The Butler Bay Coral Restoration Project, funded by the Department of Planning and Natural Resources (DPNR), is currently the only coral restoration project on the west end of St. Croix. It is a collaboration between Ceiba Strategies, LLC, a program design and project management company, and Thriving Islands, LLC, a marine research and field services company co-founded by Corina Marks and based at the Feather Leaf Inn.

Some of the Butler Bay Coral Restoration Project divers after the first day of collecting DLAB spawn in the field. Pictured from left to right: Dr. Ashlee Lillis, Lena Pine-Campbell, Kaylie-Anne Costa, Corina Marks, and Kelcie Troutman. Not pictured are Ryan Flegal, Erin Bowman, Matthew Warham, and Caroline Pott. (Photo courtesy of Thriving Islands, LLC)

Unlike most restoration efforts that focus on fragmenting existing corals to expand their footprint, the DLAB corals are produced via assisted sexual production in the lab, resulting in new corals that are genetically distinct from one another and from their parent colonies.

“When you fragment corals, you’re creating more of the corals that already exist,” says Marks. “It’s essentially a monocrop. Genetic diversity is key to creating corals that are more resilient to threats like SCTLD.”

Lab-assisted sexual reproduction is also necessary because, with fewer adult parent colonies on the reef, natural fertilization is more difficult. “Reefs in St. Croix used to persist from mass spawning events. But today, there are so few parent coral colonies, and in turn, eggs and sperm released, that it’s unlikely that coral spawning will be successful for some coral species,” says Marks.

Fortunately, DLAB coral spawning patterns are highly predictable.

“They always spawn on the 10th or the 11th day after the full moon in May and June, about an hour after sunset,” says Lillis, whose research established the DLAB spawning calendar in St. Croix in 2019.

Project divers collected gametes (eggs and sperm) from adult DLAB colonies in May. Lillis mixed the gametes in the lab to develop fertilized larvae. When the larvae settle onto a hard surface, they quickly transform into tiny corals. These new coral “recruits” will be kept in special incubation chambers in the ocean for at least a year until they are large enough to plant on the reef.

Gametes are collected in floating tubes attached to collection nets. (Photo courtesy of Thriving Islands, LLC)

Lillis believes that protecting the juvenile corals in incubation chambers, rather than planting them immediately onto the reef, will greatly increase their rate of survival. If successful, after one year, the Butler Bay Coral Restoration Project will be able to outplant 300 new grooved brain corals to Butler Bay reef – a sixfold increase in the estimated number of specimens on the reef today.

“If successful, after one year, the Butler Bay Coral Restoration Project will be able to outplant 300 new grooved brain corals to Butler Bay reef – a sixfold increase in the estimated number of specimens on the reef today.”

It will take quite some time for divers and snorkelers to see these corals on the reef, however. Corals only grow about 3 cm per year, and the new DLAB “recruits” will only be the size of a quarter when they are planted.

Juvenile DLAB corals produced through the spawning work of the Butler Bay Coral Restoration Project will grow in protected incubation chambers in the bay until they are large enough to outplant to the reef. (Photo courtesy of Thriving Islands, LLC)

Hand-rearing corals in a laboratory is a very labor-intensive process, which is why it’s important to find ways to affordably scale the work. This DPNR-funded project is the first to leverage small local businesses to develop innovative restoration methods that can be easily replicated across the territory.

“Because we have a small, local team, we can be nimble – we can quickly respond to what does and doesn’t work,” says Marks.

The project also benefits from a rich pool of skilled marine professionals in St. Croix who can support the work, according to Ceiba Strategies. This includes DPNR personnel, who provide expertise, training, and professional contacts with vendors and other organizations involved in restoration. “It’s a hugely beneficial collaboration, and it shows how committed they are to building up local capacity to restore our reefs,” the company said in an email.

The most important test of the Butler Bay project is to determine the feasibility of rearing corals without access to an expensive land-based seawater facility. If successful, the Butler Bay project could become a blueprint for scaling up restoration by working with small NGOs, dive shops, hotels, community groups, and local scientists.

Thats the key to scaling – not one organization doing everything on a larger scale, but working with smaller partners who may not be traditionally involved in coral restoration and protection,” says Lillis. Everyone who cares about corals should be able to be involved.”

Butler Bay project divers will collect more DLAB gametes during the next mass spawning event anticipated June 13-16.

For more information and inquiries about the Butler Bay Coral Restoration Project, please contact