An epidemic under the sea that is spreading more rapidly than COVID-19 among humans continues to make waves for marine biologists. The fear of a lethal coral disease spreading to St. Croix’s reefs has now become a reality.
Stony Coral Tissue Loss Disease, also called SCTLD (pronounced like “Skittled”), has impacted coral reefs in the territory since January 2019. Initially, traces of the disease were seen around St. Thomas and later spread to St. John. Now, traces have been found on St. Croix as of July.
SCTLD was first identified in Florida in 2014 and was found in reefs near St. Thomas in January 2019, according to Marilyn Brandt, a marine biologist based at the University of the Virgin Islands. “We are still not sure what causes SCTLD, but it can be a bacteria because it responds to antibiotics,” Brandt said. “There is a lot of research still happening to try and determine the actual cause. Corals are really complex in the amount of bacteria that they host.”
SCTLD affects about 18 species of coral and is particularly prevalent among brain corals, star corals and others that form the boulder-like structures that make up healthy reefs. When SCTLD attacks coral it kills the coral tissue very quickly. “The coral animal liquefies off of the hard substrate that it forms,” Brandt said.
The disease is most concerning to scientists because it is killing the framework of the reef. It makes it difficult for coral to create the reef structure used by all the sea life we associate with that ecosystem. “The fish, lobsters, all of the little sea creatures on the coral reefs are dependent on these types of coral for their homes,” Brandt said.
A “strike team” of scientists and managers are trying to combat the disease by applying antibiotic amoxicillin. The amoxicillin is mixed with a sticky base that adheres to corals for several weeks, and with repeated treatment and some luck, the disease does not spread beyond the treated area.
“With coral, they can’t develop immunity; you can’t give a coral a vaccine because they do not have that component of an immune system,” Brandt said. As far as the application of antibiotics, the problem is that hundreds of thousands of corals are affected. “One diver can only treat like ten to twenty corals in a single dive and therefore, we are trying to focus our efforts on sites that are becoming newly affected. We are trying to treat as many corals as possible early on,” Brandt said.
“It is very similar to what we did with COVID-19 at the beginning,” she continued. “We shut everything down, and you try to prevent as many new cases from starting because once it gets going, it’s like a fire.” The strike team is currently focusing their efforts on sites of high importance that they know are diverse in coral. “Sites that we can access and get to frequently so we can treat as much as possible,” Brandt said.
At UVI, researchers have also begun collecting smaller corals that can be affected by the disease. “We were able to cure them in the lab and placed them in clean water,” Brandt said. They are rescuing and treating so many different types of corals that they are running out of space in their water table, she said. “Coral World Ocean Park has therefore begun taking the ‘rescued coral,’ and creating an exhibit for them,” Brandt said. The ultimate goals are to place them back into the ocean where they can do what they do best, which is contributing to the coral reef once more.
Brandt said she is very concerned about the future of the reefs in the territory. Fifteen years ago, in 2005, the reefs were affected by a hot water event. “Some of the reefs haven’t even recovered since that event, and now with SCTLD, we have lost more coral than we did in the previous event. There doesn’t seem to be an end to the loss of coral,” Brandt said.
Snorkelers and divers who are interested in assisting are encouraged to report anything strange on the reef at the website vicoraldisease.org. There, they can drop a pin on a map with the location where SCTLD may have been seen. SCTLD can also be confused with bleaching, which occurs when corals shed the symbiotic algae which give them their color. Bleaching events are often seasonal and result from rising water temperatures and other environmental stressors. Corals can recover from bleaching if the stressor is removed within a few weeks, but SCTLD is almost immediately lethal. For a full explanation, see the strike team’s website.
Anyone interested in volunteering can visit the C.O.R.E. website. “These are Virgin Islands cultural treasures, and people should know that this is happening to them and there may be long-term impacts from the loss of so much coral,” Brandt said.