A coral disease outbreak that wiped out nearly 80% of stony corals between Florida’s Key Biscayne and Key West during the past two years appears to have spread to the U.S. Virgin Islands (U.S.V.I.), where reefs that were once vibrant and teeming with life are now left skeleton white in the disease’s wake.

The fast-spreading disease—believed to be Stony Coral Tissue Loss Disease (SCTLD)—has marine scientists scrambling to understand what’s causing the outbreak and how or if it can be contained.

“The disease is affecting a variety of reef-building coral species—many of them long-lived—and appears to be spreading from reef-to-reef throughout southwestern St. Thomas,” said Amy Apprill a marine ecologist at Woods Hole Oceanographic Institution. “It’s the worst multi-species coral disease we’ve ever seen in the Caribbean, and most of the corals that get it die.”

Rapid response

St. Thomas and the other U.S. Virgin Islands depend on corals for tourism and food, and to buffer coastlines from storms. With funding from a Rapid Response Research (RAPID) grant through the National Science Foundation, Apprill, along with colleagues from the University of the Virgin Islands, Rice University, Louisiana State University, University of Texas at Arlington, and Mote Marine Laboratory, are conducting a task-force style investigation to learn more about the disease’s pathology, how it may be spreading through the ocean, and how coral immune systems are responding to it. The researchers are also trying to determine if the outbreak can be stopped before it completely decimates reef ecosystems throughout the region.

“At this point, there’s no end in sight,” said Apprill.

According to Dan Holstein, a coral reef ecologist at Louisiana State University, it’s unclear how the disease has spread from South Florida to the U.S. Virgin Islands. “We don’t see an immediate link or reason it would have travelled south,” he said. But he suspects that it could be spreading through the region from boat ballast water or ship hulls. “One reason we’re looking into this is that the first observation made of the disease in the Virgin Islands was very close to the port of St. Thomas, where ships drop their ballast water,” he said. “Based on this hypotheses, we’re creating hydrodynamic models to predict where the disease might move next now that it’s established in the region.”

Similar signs to Florida outbreak

Regardless of how it got to the Caribbean, the researchers feel that the disease they’re seeing is the same one that caused the loss of nearly 100,000 acres of corals in Florida over the past five years. Most of the U.S.V.I. corals that have been affected so far—brain corals, pillar corals, and other stony species—have exhibited the same types of large, stark-white lesions as those affected in Florida.