Coral disease spreads in Caribbean

Red areas indicate areas of confirmed stony coral tissue loss disease in the Caribbean and Straits of Florida.
Red areas indicate areas of confirmed stony coral tissue loss disease in the Caribbean and Straits of Florida.
Red areas indicate areas of confirmed stony coral tissue loss disease in the Caribbean and Straits of Florida.

Stony coral tissue loss disease (SCTLD), is now seen in Caribbean reef areas and in nearshore reef areas. First identified in Florida in 2014, SCTLD has become prevalent across the Caribbean tropics, affecting more than 30 varieties of corals. One problem is confusion with coral bleaching, a process caused by water temperature/UV sunlight damage. The white patches on corals look similar, but one is a stress response while the other is an infection. There are several papers to assist in coral disease identification, such as the Atlantic Gulf Rapid Reef Assessment (AGRRA) presentation at (click on “Coral disease outbreak” and then scroll down to “How do I identify it?”). Or see the downloadable image cards at (click on “Stony Coral Tissue Loss Disease”).

Per AGRRA, at least 20 Caribbean countries have confirmed SCTLD infections, 19 countries are being monitored, and 11 have SCTLD treatment efforts in progress. This disease has affected the pillar, brain, star, and starlet coral species; it is rapidly spreading with a high mortality rate. The disease kills coral colonies, with its hallmark signature of a “coral skeleton devoid of flesh.” The diseased coral has discolored stark white patches. While there are several coral diseases, SCTLD has become the major topic of scientific coral studies in the Caribbean. Scientists have not discovered SCTLD outside of Caribbean areas such as the Caribbean islands, Gulf of Mexico, western Caribbean and Florida, but are researching reports to their websites. 

Areas with confirmed SCTLD infection include USA/Florida, Jamaica, Mexico, Sint Maarten, the US Virgin Islands, Dominican Republic, Turks & Caicos Islands, Saint Martin, Belize, Sint Eustatius, The Bahamas, Puerto Rico, British Virgin Islands, Cayman Islands, Guadeloupe, St. Lucia, Honduras, Roatan and Martinique.

To combat SCTLD, new treatment approaches have shown success utilizing a disinfection procedure for divers and an antibiotic paste, amoxicillin, manually spread on infected corals. The antibiotic treatment has shown hopeful results, stopping infection from spreading over the entire coral. As this requires professional training plus diving to treat the coral underwater, the procedure is only able to support a small subset of infected corals. 

Success with antibiotics is also indicative of a potential bacterial cause. One report suggests the cause may be due to untreated sewage. The topic of sewage is a sensitive one, but there are other areas with large commercial vessels/and or diving spots that are infected. As divers are advised to disinfect gear with a light bleach solution, bilge water could also be treated. Regarding holding tanks, no tanks should be dumped over shallow coral areas. More of an issue may be near shore, where local sewage disposal and shore runoff may drain directly into the harbors. 

Coral disease research has become a major   effort across the Caribbean. Researchers and organizations are trying to understand the extent of damage and are attempting to discover treatment approaches to save coral species. Some governmental and non-profit organizations participating in this research include the NOAA Coral Reef Watch program (, AGRRA and the Gulf and Caribbean Fisheries Institute (

Several organizations with major research efforts have been identified below along with their various digital desktops. Cruisers will find the desktops accessible via the Internet, open to all for reporting and information on locations of concern. Some sites may allow email reports, but this is case by case. There are three sites accepting citizen scientist observations. Go to: GRRA, Florida SEAFAN, or VI_CDAC.

By reporting to the research sites, boaters can help organizations develop maps of infections. This then leads to gaining more information on rate of spread and may assist in validating successful treatments. Organizations hope cruisers can help identify potential causes, treatments, and additional ways to alleviate this disaster occurring in our beloved tropic waters.

Joan Conover (president of Seven Seas Cruising Association)