Rapid spread of deadly disease killing up to 94 percent of Caribbean coral species

A new coral disease is quickly circulating in the Caribbean, killing as much as 94 percent of certain types of coral species in the region, according to a study published Thursday in the journal Communications Biology. 

Researchers found that an outbreak of stony coral tissue loss disease (SCTLD) that was first reported in Florida in 2014 is likely to become “the most lethal disturbance ever recorded in the Caribbean.” The outbreak reached the northern Mesoamerican Reef, the largest barrier reef in the Western Hemisphere, off the coast of Mexico, Guatemala, Belize and Honduras by summer 2018 and spread across the entire roughly 450-kilometer reef system within a few months, according to the study. 

Out of more than 29,000 coral colonies the researchers surveyed between July 2018 and January 2020, 17 percent showed signs of having died recently by the time of survey. An additional 10 percent had been affected by the disease. 

The researchers said the area is a well-known “hot spot” for diseases, many of which have significantly reduced coral populations in the past. One outbreak of another disease in the late 1970s led to the loss of almost 80 percent of two major reef-building corals, reducing the functionality of the reef. 

The researchers also said that human-induced factors like rising sea levels and reduced water quality are increasing the risk of diseases that disrupt an ecosystem’s stability. They said environmental conditions, such as nutrient concentrations, likely influence the prevalence of SCTLD, though higher water temperatures appear not to have a direct effect. 

“SCTLD now threatens many coral species that serve as important reef-builders and habitat providers in most of today’s Caribbean reefs,” the study states. 

The researchers did take note that the prevalence of the disease was worse closer to areas with coastal development. Most sites that are experiencing more than 50 percent prevalence were located in the northernmost region, which has the most urban areas, hotels and tourist spots that cause pollution and runoff, researcher Lorenzo Álvarez-Filip told The Washington Post. 

Reefs often provide habitats for other animals, so corals’ death can have significant harmful effects on other organisms in the ecosystem. 

The researchers said a key question for the future is if the species most affected by the disease will be able to recover and continue to play its role in sustaining the ecosystem. They said the replacement of dead coral would take several years because most species grow at slow rates. 

They concluded that human intervention to rescue coral colonies, preserve their genetic material and try to restore species will be necessary to prevent some types of coral from going extinct. 

“We believe, however, that these actions will only succeed if they are accompanied by stringent controls that take into consideration climate change, coastal development, and wastewater treatment to improve local conditions and ecosystem resilience,” the study states.