A mysterious ‘plague’ is destroying coral reefs – and scientists are struggling to find a cure

The building blocks of the undersea infrastructure are being decimated by a mysterious plague. And no one is sure how to stop it.

Off the coast of St. Thomas in the U.S. Virgin Islands, a group of scientists is tearing a reef apart in a feverish attempt to save some of its coral.

They are battling a fast-moving, lethal disease that researchers say is unprecedented in the speed with which it can damage large numbers of coral species across the Caribbean Sea.

Breaking their cardinal rule to never touch the coral, the scientists are removing diseased specimens to try to stop the disease spreading and save what remains.

Meanwhile, researchers and divers in Florida, where the disease was first spotted in 2014, are also removing coral samples and shipping them to places as far-flung as Kansas and Oklahoma, in a last-ditch effort to save the 20 species or more thought to be susceptible to what has been dubbed Stony Coral Tissue Loss Disease.

Ravaged reefs

Stony Coral Tissue Loss Disease was first observed around Virginia Key near Miami in 2014. It spread to the northernmost extent of the Florida coral reef tract by 2017 and has now extended past Key West to the south.

The disease prompts rapid tissue loss, appearing first as white patches that sprawl out across the coral, before eventually stripping it of color and life altogether.

About half the coral species that make up Florida’s reef tracts and about a third of those throughout the Caribbean are vulnerable to the disease, at a time when the delicate ecosystems are already threatened by climate change.

Overall, Florida’s Upper Keys have seen greater than 40% loss in coral cover between 2013 and 2018, according to the Florida Fish and Wildlife Commission.

Stony Coral Tissue Loss Disease has been identified in seven other Caribbean localities, according to the Florida Sea Grant, a university-based program funded by the federal government. Unlike the more well-known coral bleaching phenomenon, coral typically cannot recover from Stony Coral Tissue Loss Disease. The species fall victim to it at different paces, with a mortality rate of 66-100 percent.

“I have never seen anything that affects so many species, so quickly and so viciously — and it just continues,” said Marilyn Brandt of the University of the Virgin Islands, who is one of the researchers involved in the efforts to save the reefs near St. Thomas.

Coral anatomy

Pillar coral are composed of colonies of up to thousands of small polyps that grow slowly over hundreds of years. They feed via a symbiotic relationship with the algae (zooxanthellae) in their skin, slowly forming a limestone skeleton that helps provide shelter and breeding grounds for aquatic life.

“All the diseases I’ve studied in the past could be considered like the flu. They come every year, seasonally, and sometimes there are worse outbreaks. This thing is more like Ebola. It’s a killer, and we don’t know how to stop it.”

Brandt’s team first spotted the disease along the west coast of St. Thomas in January and have launched a frantic effort to try to stem its advance, resorting to removing diseased corals with a hammer and chisel to try to salvage the rest.

“The coral basically liquefies from the inside out,” Brandt said.

Weakened system

The disease was first identified near Miami, Florida, where the port was conducting a dredging project, and has now spread throughout almost all of the state’s reef tract.

The coral in the area were already stressed from the dredging and a recent bleaching event, so it was unsurprising they got hit with a disease, the scientists told Reuters. Like with a human body, a weakened immune system can make coral more susceptible to disease.

“All the diseases I’ve studied in the past could be considered like the flu. They come every year, seasonally, and sometimes there are worse outbreaks. This thing is more like Ebola. It’s a killer, and we don’t know how to stop it.” Marilyn Brandt, Research Associate Professor, University of the Virgin Islands.

“We tend to just study these events. We monitor them. We try to research what to do. We just watch it happen and assume that Mother Nature is going to be able to take the reins and everything’s going to be fine,” said Maurizio Martinelli, Coral Disease Response Coordinator at the Florida Sea Grant.

But the scale of the new disease has led to a more urgent approach. Large coral individuals that scientists have estimated to be hundreds of years old have been dying within a matter of several weeks, according to the scientists’ estimates.

“We can’t just watch these corals all die in front of us,” Martinelli said.