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That’s part of the reason Naval Information Warfare Center (NIWC) Pacific scientists have been researching a way to improve coral survivability for coastlines where coral and the Navy are neighbors. Thanks to the team’s innovative housing structures—or “Coral Arks”—they’ve improved survival rates of translocated coral by 38% during the past nine months compared to traditional methods.
“It’s going so well that not only are most of the corals happy and healthy, but they also survived a hurricane that recently passed over Puerto Rico,” said Jessica Carilli, who holds a doctorate in Earth science and is principle investigator for the Coral Arks Project NIWC Pacific is leading in Vieques, Puerto Rico.
The project aims to provide an improved method to mitigate damage to coral reefs, which are protected by many federal statutes. The idea for the Coral Arks method initially came from Carilli’s colleagues at Harvard University and San Diego State University; now she’s leading collaboration for its Department of Defense-funded field testing.
Mitigation typically entails simple methods, such as removing coral from piers and placing them on nearby surfaces where corals don’t already live. But Carilli pointed out the flaw in this method: if there aren’t corals living there, it’s probably not where they want to be, and they’ll soon die. If mitigation isn’t effective enough to meet requirements, regulatory agencies may mandate other in-kind mitigation measures, such as upland watershed restoration.
It costs time and money to execute and monitor multiple attempts at coral reef protection. Now, the Coral Arks team’s methods could save time, money, and coral lives.
With the Coral Arks method, coral thrive in housing structures placed in areas of higher water quality. In water farther from the shore, land-based runoff is more diluted, so water tends to be clearer from excess nutrients, agricultural chemicals, and heavy metals.
Because corals need sunlight, they can’t grow as well in these deeper waters, but Coral Arks solve this problem by situating corals just 25 feet below the surface. It’s a simple idea, Carilli said: “Let’s build a coral habitat in places corals like to grow.”
Coral is epoxied onto the coral plates, or limestone tiles, housed by arks floating midwater; in the control group, coral plates are deployed directly on the seafloor. Two Coral Arks house 100 corals each as part of the testing in Vieques; another 200 are distributed throughout control sites.
In the long term, it could be more cost effective to build and deploy the simple housing structures, which were designed for durability and longevity. In turn, the arks improve durability and longevity of corals, contributing to their long-term health. And the more agencies and other coral reef neighbors implement the Coral Arks method, the stronger their symbiosis with ocean habitats.
“I really love that part of this job,” Carilli said. “I feel lucky at NIWC Pacific because we work directly with the people, the installations, that have a need. We use science to help them figure out how we can solve it—and when we do, we make a real difference.”
Meeting federal statutes about coral protection more efficiently means the Navy can expand the scale and scope of its activities in an environmentally responsible way. It’s a small part of NIWC Pacific’s information warfare and research and development missions, and its potential to spread to other places where coral and the Navy are neighbors could create a sizeable impact.
Carilli and her team will continue monitoring coral in their arks and in the control group for the next year, tracking survival and growth rates, water quality, fish biomass, and other health metrics. The project concludes in June 2024, when the team will compile their findings from two years of field testing. At the end of the project, the team hopes to contribute the arks to organizations committed to their maintenance as coral nurseries.
Carilli’s favorite thing about coral? “They associate with algae living in their tissues, that’s why they’re colorful. That symbiosis is pretty well known.” But, Carilli explained, many other organisms live in and on coral. Fungi and algae live in their skeleton, “and there’s tons of different microbes that live in the mucous layer on the outside of the coral.”
“It’s becoming more well-known that coral are these ‘holobionts’—an organism plus its essential symbiotic partners,” Carilli said. “And that the coral can’t really survive without all of it working together.”