Subscribe to North America's Longest Established Scuba Diving Magazine
Conservation Destinations Marine Technology

SCTLD: The other pandemic

Stony Coral Tissue Loss Disease is spreading rapidly, decimating Atlantic and Caribbean coral colonies within weeks of infection – and scientists still don’t know what’s causing it

Divers apply a unique epoxy mixture to coral affected by SCTLD.

Words and Photography by Nicole Webster

While humans are battling a relentless pandemic, the corals of the Atlantic and Caribbean are suffering from their own relentless disease: Stony Coral Tissue Loss Disease (SCTLD). SCTLD is a disease so deadly, it can wipe out a 200-year-old coral colony within two months of infection. 

What began in the waters of Miami-Dade County in 2014 has since spread from the Florida Reef Tract to the Mesoamerican Reef via currents, ballast water, and direct contact. As of November 2021, SCTLD has been confirmed in 20 countries and territories.

One of the most recent countries to be hit by this coral epidemic is Honduras. Just off the northeast coast lies an archipelago, consisting of three main islands, Roatán, Útila, and Guanaja. Along with a group of cays named Cayos Cochinos, this marine protected area of Honduras is known as the Islas de la Bahía, or the Bay Islands. 

Throughout the years, the corals of the Bay Islands have suffered through bleaching events, the lionfish invasion, and some of the most notable coral disease outbreaks. White band disease, for instance, decimated Caribbean acroporas in the 1980s and 1990s. After all, disease is a common occurrence in any reef ecosystem. 

“Corals are animals just like you and me. They contract diseases in the same way. When you are healthy, your body is able to fight off bacteria and viruses. When you are stressed, your immune system is weakened and you are more susceptible to diseases,” said Andrea Izaguirre, a member of the SCTLD Response Team in Útila. 

Coral diseases are not new. Since 1972 when coral diseases were first officially recognized, scientists and conservationists have been working tirelessly on coral research, treatment, and restoration. Yet the outbreaks keep increasing, both in quantity and severity. 

“Stony coral tissue loss disease is a coral disease of the likes we have never seen before,” said Alex O’Brien, marine biologist and GoEco Program Director at Útila Dive Center. 

SCTLD has everyone in the Caribbean on high alert for a number of reasons. It is hard to diagnosis, no one knows exactly what is causing it, it spreads and kills incredibly fast, and it affects a high number of species, specifically reef builders. 

Reef builders are special because they make up the three-dimensional structure of a reef. Imagine going diving and seeing flat topography, an abundance of soft corals, and fewer fish. 

There are more than 30 species of stony corals found in the Bay Islands. SCTLD affects 22 of them. The disease has a lot of potential for dramatic and lasting changes, and not just in biodiversity. Local communities and tourism will see a negative impact as well. 

If you look closely at inefected coral, you can see tissue dissolve before your eyes

Red alert

For the past seven years, the Caribbean and Western Atlantic have watched SCTLD spread throughout the region. Scientists closest to ground zero in Florida have been scrambling to come up with answers. All eyes are on Florida. Any information or advice is quickly shared to prepare countries for when (not if) the disease hits their corals.

“Everyone is on red alert. There’s a regional harmony. I am seeing a lot of support and communication from many other countries. Everyone is working together to try and find a solution,” said Andrea Godoy Mendoza, Marine Conservation and Social Development Coordinator for Fundación Cayos Cochinos. 

A great deal of what is known of SCTLD was learned through time and experience. Florida has categorized the disease into four outbreak stages: pre-invasion, invasion, epidemic, and endemic. The Bay Islands, collectively, are currently experiencing all four stages at once. 

Roatán, the largest and most well-known of the Bay Islands, was hit first. In September 2020, a citizen scientist reported a sighting to the Roatán Marine Park. Thanks to photos the diver took, it was quickly confirmed. 

The confirmation of SCTLD came as no surprise; in fact Roatán had been waiting—even preparing—for it. Roatán Marine Park began spreading awareness through campaigns and webinars a year before the disease reached the island. They prepared themselves with plans of action for monitoring and had the necessary documentation on stand-by in order to apply for the permits required to purchase supplies for treatment. 

In reality, there is only so much preparation you can do. “We prepared the ground, but when it came, we had to learn through doing. This whole year has been about learning through doing,” said Damaris Duenas, biologist and Research Associate for Roatán Marine Park. 

The rest of the Bay Islands watched and waited for nearly a year. The non-governmental organizations responsible for managing the marine protected areas stayed in constant communication with one another. Roatán Marine Park became the main source of information for the smaller islands. 

Another preparation method that was implemented was disinfection protocols, partly dispersed through SCTLD awareness campaigns, but it was also the new standard amongst dives shops because of COVID. 

Dive shops have been asked to disinfect all dive gear at the end of every dive and in between dives on surface intervals in a 0.5% bleach solution. It is also recommended that when choosing dive sites to visit, first go to an unaffected site, and an affected site second. Although not proven, there is strong evidence that divers unknowingly spread the pathogen from dive site to dive site through scuba gear. 

After nearly a year, SCTLD was unfortunately spotted on Útila’s northeast side by O’Brien and confirmed by the Bay Islands Conservation Association (BICA) in Útila on June 27, 2021. Monitoring it closely, Útila can confidently report that in just four months, it has encircled half the island. 

Officially, SCTLD monitoring around Útila happens once a month. However, on an island where dozens of divers are in the waters all day, every day, it has become an all-hands-on-deck situation. 

The Atlantic and Gulf Rapid Reef Assessment (AGRRA) online dashboard is an excellent resource for monitoring and further education

Identification and treatment

BICA has asked divers for help.  Any diver who suspects the disease is asked to submit a photograph along with the location of the dive site. These preliminary monitoring methods are crucial in diagnosing the initial impact, especially when you have a disease that spreads faster than official monitoring can take place. 

Monitoring for SCTLD is done in one of two preferred methods. The first is the manta tow method, effective most during the invasion and endemic stages and used to cover large areas. This is where a diver is towed by the boat and gets dragged across the surface of the water, observing the reef from a bird’s eye view. 

The second method, the roving diver, is used for a more detailed account of the disease, which is why it is best during the epidemic phase. A team of two to four divers visit sites with SCTLD, count and document infected colonies, and use these numbers for quantifiable data. 

Útila is currently entering into the worst phase, the epidemic. A huge indicator in diagnosing SCTLD is that when the invasion stage occurs, it first attacks the highly susceptible species. 

There are eight species that are considered highly susceptible, but the grooved and boulder brain corals, as well as pillar, are the most notable. Pillar corals are especially revered due to their endangered status and rarity. Sadly, Florida recently reported a regional extinction of pillar corals in the Florida Tract due to SCTLD. 

Cayos Cochinos was the last of the Bay Islands to confirm and report the disease. It has only recently confirmed SCTLD presence at one, semi-contained site, a seamount called Roatán Banks. The invasion is only just beginning for this highly protected marine area but monitoring and treatment efforts have already begun. 

“I remember diving the site [in September] and being blown away. I was actively looking for signs of the disease and did not really see any. Going back a couple months later and seeing all the colonies affected in such a short amount of time, it hit hard,” recalled Godoy Mendoza. 

An epoxy is prepared by volunteers, mixing a jar of Base2B with 50 grams of amoxicillin. The mixture is transferred into half a dozen syringes before being applied

Immediately prior to a treatment dive, an epoxy is prepared by mixing a jar of Base2B (a specially designed paste by the Ocean Alchemists) with 50 grams of amoxicillin. The mixture, sticky and thick, is transferred into six to seven catheter syringes. It is very important to keep the medicine chilled until you are ready to use it.

Armed with the epoxy-filled syringes, trained divers go to SCTLD confirmed sites and choose approximately a dozen corals to treat. Corals are chosen by size and number of lesions. If a coral is too small, relative to its sexual maturity, or the rate of infection is too high, it is not worth treating. 

The medicine is applied by hand, directly onto the coral, following the edge of where the dead tissue meets the healthy tissue. If you look closely enough at a coral with active SCTLD, you can see the tissue literally dissolving before your eyes.

Although no pathogen has been confirmed, the culprit is suspected to be a bacteria. This is based on the fact that antibiotics seem to be the only thing proven to halt the spread of the disease. 

This treatment is not a cure, it is only a method used to slow the progression. Success rates of the treatment also vary among coral species. 

“When we treat the lesions, we are only helping that one wound. It does not mean that colony has now gained some immunity,” said John Bodden, Research Coordinator at Útila Coral Restoration. 

The epoxy, specifically the Base2B component, must be purchased by registered and approved entities. Each of the Bay Islands are required, by the Gulf and Caribbean Fisheries Institute, to obtain separate permits in order to purchase the epoxy ingredients, and to apply the treatments. 

Above all, the epoxy is expensive. One jar of Base2B costs $50 and has a shelf life of three months. 

Roatán has spent about $14,000 in the last year just on Base2B. This does not include the costs of the amoxicillin, the materials, the dive equipment, the boat, or the staff needed for treatment dives. 

The epoxy mixture is applied to the edges of the infected coral by trained, volunteer divers. The mixture is not a cure, but does slow down the progression of the disease

Hope ahead

Data and numbers from Roatán are still being collected and interpreted. The main question on everyone’s mind is, “Have Roatán’s treatment efforts been successful?” As the epidemic stage begins to shift into the endemic stage, Roatán has become a sort of guiding light to the other Bay Islands.  

“Not everything is lost. There are still corals that are thriving and resilient. They are still spawning. This is a great loss for colonies but there is still hope,” said Duenas, reminiscing on a recent dive Roatán Marine Park conducted to document coral spawning. On this dive, two pillar corals that had been infected and treated were seen spawning, a small but important victory. 

Coral reefs are strong beyond human measure. It is in their DNA to protect other species and coastlines. Throughout history, they have continued to evolve through Earth’s most devastating phases. Big changes to the world’s coral reefs are unfolding before our eyes, exacerbated by stress from pollution and global warming. 

One of the hardest jobs of a conservationist is the ability to see the positives, no matter how dire the situation can get.

“It feels like it is going to last forever. The only thing that is going to help is to work together. To create more restoration efforts. Treating is only a Band-Aid. We need to think towards the bigger steps of restoring our reef,” said Duenas. 

A collective consensus among the Gulf and Caribbean countries has been born from years of dealing with SCTLD. What needs to happen next is more coral restoration efforts. 

“Don’t take SCTLD as it’s too late, we can’t do anything more for it. It is presenting an opportunity to call for more help in coral restoration. Knowing that there are some corals that have resilience gives hope that the reef will keep on fighting. We just need to do what we can to assist it,” said Bodden. 

To track the disease visit:

For more on the Bay Islands: www.

For more from Nicole visit:

1 Comment Leave A Reply

One Response to “SCTLD: The other pandemic”

  1. Louis Brignet

    I haven’t seen or recently heard of this really nasty coral bleaching going on off the coast of Belize which is where I’m headed in June.


Leave a Comment

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.