At the beginning of the year, divers watching the coral reefs near St. Thomas, in the Virgin Islands, noticed alarming white lesions feeding on the colorful fabric of the labyrinthine corals of Flat Cay. They are injuries caused by a deadly disease that is expanding unstoppably across the Caribbean.
A day after the observation of this disease, some corals had already died and only their white skeletons remained. Others languished during the next two weeks and, in just four months, more than half of the reef had disappeared. The main suspect is the disease known as SCTLD or by its nickname skittle-D. It is an infection discovered in Florida in 2014 and is responsible for what some scientists consider one of the deadliest outbreaks ever recorded.
What researchers still do not know is whether the disease is viral, bacterial or any other microbial mixture. Whatever the cause, it is annihilating the entire species, says coral ecologist Marilyn Brandt, who leads a scientific team from the University of the Virgin Islands that tries to address the outbreak from multiple research angles.
Previous outbreaks of other coral diseases near St. Thomas had already reduced the coral by half. “This new disease has already caused the same amount of damage in half the time,” says Brandt, who says the concern is serious. Although coral reefs occupy less than 2% of the seabed, they play a crucial role in the ecosystem and support about a quarter of the ocean’s species.
In southeast Florida this same disease has been treated by a team of marine biologist Karen Neely, of Nova Southeastern University in Fort Lauderdale, with a disinfectant and a paste of amoxicillin, which seems to cure the lesions. Researchers have used this medicine in almost 1,200 colonies since January, although they have not been able to prevent the appearance of new lesions. The effectiveness of the antibiotic suggests that the disease could be bacterial, according to Brandt. “But it could have viral origins, in which case the paste would treat a symptom, not the cause.”