Stony coral tissue loss disease


Stony coral tissue loss disease is a disease of corals that first appeared off the coast of Florida in 2014. By 2019 it had spread along the Florida Keys and had appeared elsewhere in the Caribbean Sea. The disease completely destroys the soft tissue of many species of stony coral, killing them within weeks or months of becoming infected. The causal agent is unknown but is suspected to be a bacterium. The degree of susceptibility of a coral, the symptoms, and the rate of progression of the disease vary between species.

History

The disease was first detected in late 2014 when a few corals off Virginia Key, in Miami-Dade County, Florida, were affected. By the following year, the disease had spread and extended from Pompano Beach to Biscayne National Park. In 2016 it reached Palm Beach County, Florida, and the upper Florida Keys, and the next year the lower Florida Keys. By August 2018, the disease had spread over of sea, and almost half the species of coral growing in the Florida Reef Tract had been affected. By January 2019 it had been reported from Jamaica, the Mexican Caribbean, Sint Maarten, and Saint Thomas, U.S. Virgin Islands.

Signs

The signs of this disease are somewhat variable, and it may be difficult to distinguish from other coral diseases. Infections generally start near the base of the coral with the soft tissue dying, a band of diseased tissue progressing across the surface. Sometimes the infection exhibits a series of blotches that radiate outwards and coalesce. Small corals may be killed within weeks while larger individuals may survive for months or even a year or two.

Research

This is a particularly deadly coral disease with mortality rates varying between 66% and 100%. Although the cause of the disease has not yet been established, evidence suggests that a bacterial pathogen is being transmitted either by contact or by means of water movement. Not all corals are susceptible to the disease, with staghorn coral and elkhorn coral, both of which are critically endangered, appearing to be immune.

Susceptibility

The first species on a reef to be infected are usually the meandroid corals such as pillar coral, elliptical star coral, smooth flower coral, and maze corals. Other susceptible species include boulder brain coral, grooved brain coral, smooth flower coral, maze coral, symmetrical brain coral and knobby brain coral.