The Caribbean Sea is battling an epidemic—a nasty plague that spreads and kills quickly. This so-called white plague is devastating populations of marine corals.
Scientists long believed the scourge, which first popped up in the 1970s, had strictly bacterial origins, but research now suggests viruses may play a prominent role in causing white plague. During a 2010 white plague outbreak in the Virgin Islands, researchers analyzed the viruses present in diseased and healthy corals. While all of the sampled corals carried numerous viruses, the tissue taken from corals that had white plague predominately contained one, specific group of viruses. Known as small, circular, single-strand DNA viruses (SCSDV), these could potentially have caused the disease.
The results are an important step forward in understanding both white plague and coral diseases in general, said University of Pennsylvania biologist Mónica Medina, who wasn’t involved in the study. “We, as a scientific community, have neglected the study of coral viruses and their role in host health for too long,” she told LiveScience.
What is white plague?
White plague is characterized by rapid tissue loss, which exposes the white skeleton of the coral. “White plague is not that difficult to tell apart from other coral diseases,” said Nitzan Soffer, a microbiologist at Oregon State University and lead author of the new study. “You have living, healthy tissue, and then immediately below that you have a straight band of white on the bottom of the coral.” This white band quickly expands upward to the rest of the colony.
Researchers first identified white plague in 1977 in the Florida Keys, but the disease wasn’t much of an issue at the time. “It was just this new thing that people were noticing,” Soffer told LiveScience. The disease re-emerged in the same reefs in 1995 and quickly spread — scientists had reported white plague outbreaks throughout the Caribbean by 2001, according to the World Conservation Monitoring Center. Recently, outbreaks of white plague have wiped out 70 to 80 percent of some Caribbean coral reefs, Soffer said.
Scientists currently recognize three types of white plague that differ in how quickly the disease progresses. Type I, the variety identified in 1977, causes coral tissue mortality at a rate of about a tenth of an inch (3 millimeters) per day. Type II, identified in 1995, progresses at up to 0.8 inches (2 centimeters) per day and can kill a small colony in one or two days. First identified in 2000, type III causes tissue loss at more than 0.8 inches a day and mainly affects the largest reef-building corals, including mountainous star coral (Montastraeafaveolata) and giant brain corals (Colpophyllia natans). [. . .]