TCRF tests alternate, non-antibiotic treatment against SCTLD.

Story & Photos By Alizee Zimmermann, Turks & Caicos Reef Fund

From wreaking havoc on the Florida Reef Tract to now threatening the stony coral population of reefs in 17 countries and territories, Stony Coral Tissue Loss Disease (SCTLD) is proving itself to be the most aggressive, virulent and indiscriminate coral disease in the Atlantic/Caribbean region to date. 

“Stony Coral Tissue Loss Disease (SCTLD) is a new lethal disease first reported in Florida in 2014. The cause of the disease is unknown but it is affecting more than 30 species of corals especially brain, pillar, star and starlet corals. The disease spreads quickly causing high coral mortality. Since then, outbreaks of SCTLD have been confirmed in the Caribbean off 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 and Martinique.” (https://www.agrra.org/coral-disease-outbreak/)

As I attempt to wrap my head around what has happened in the past two-plus years since SCTLD first appeared on the reefs of the Turks & Caicos Islands, I suddenly realize that it was two years to the day that I had my first face-to-face encounter with an invasion zone at the far south end of West Caicos. That day changed everything. Before May 23, 2019, I had never heard of Stony Coral Tissue Loss Disease. Two years later, it is a focal point of my career and my life. 

I’m not special or unique; there are dozens of people across 17 nations—scientists, researchers, government officers, NGO staff, citizen scientists, scuba divers, volunteers—whose lives have all shifted focus, who have been on the frontlines of an unseen, underwater battle. We share a mutual sadness.

As stated in previous articles, SCTLD was first observed by the School for Field Studies (SFS) in South Caicos in January 2019. Since then, it has spread locally to all the fore reefs of the Turks & Caicos Islands, now having been confirmed on the reefs of East Caicos in March 2021. (Initial invasion date undocumented but evidenced to be some time earlier based on observed coral mortality.)

The School for Field Studies has collected extensive baseline data on the reefs of South Caicos and in February 2021 published a paper comparing the average percentage of live coral cover between 2012–2018 to the one-year post-SCTLD live coral cover recorded in 2020. These studies indicate a 60+% loss of live coral cover on the reefs studied.

Once again, we are not alone. St. Thomas recorded 34% loss of live hard-coral cover in the span of four months in 2019, attributed to SCTLD. These numbers are being repeated on reefs across the region. Not only is this disease deadly and often resulting in entire colony mortality, it is also spreading like wildfire through the water column, able to infect large tracts of reef in very little time. 

Research into transmission vectors is still ongoing but it has been affirmed that that the pathogen(s) is waterborne and can be carried by dive gear (especially neoprene and the inner bladder of a BCD), as well as through ballast water from recreational and commercial vessels.

The T&C Reef Fund is trial testing a new treatment against Stony Coral Tissue Loss Disease.

Although hit hard, scientists and managers in the TCI are also fighting hard to track, treat and manage SCTLD locally as well as continuing to participate in the regional conversation and effort. An incredible line of communication and collaboration has opened amongst managers and scientists, governments and NGOs, neighbouring islands. The Turks & Caicos Reef Fund (TCRF) has been working alongside the Department of Environment & Coastal Resources (DECR) to test trial different intervention and treatment methods as well as the continued tracking of disease presence. 

You may remember an article on the success of the treatment used by multiple strike-teams region-wide— amoxicillin mixed into a specially designed paste called Base2B. This intervention method continues to be the most effective at halting disease progression across a colony. In TCRF’s Final Status Report based on a permit received to test the efficacy of antibiotic treatment, up to a 90% success rate was still being recorded in up to six months of monitoring.

TCRF currently has a Scientific Research Permit allowing us to expand our intervention efforts and treat large, priority colonies along the reef tract. If you see a tagged coral asking you to photograph it and email to SCTLD@tcreef.org, please do! This project aims to engage divers and citizens to help us in a wider monitoring effort. We can’t be everywhere at once, but with an active local dive community, we’re hoping to engage opportunistic monitoring of our expansion efforts.  

Alongside this effort, over the past month, we have started testing an alternative, non-antibiotic treatment created by Ocean Alchemists, the same company that developed the Base2B currently used. TCRF has been working closely with the team at Ocean Alchemists and we were excited for the opportunity to be the first to test trial their newly developed non-antibiotic treatment on SCTLD in the field. This particular treatment has had notable success against Black Band Disease in the labs at the MOTE Marine Laboratory in Florida. It is an all-natural, non-antibiotic proprietary formula (it smells like Christmas with a heavy cinnamon component!) that has been imbued into flat braided hemp ropes which are then stapled into the coral along the lesion margin. In May 2021, TCRF tagged approximately eighty colonies along three transects on the dive site Catacombs in Grace Bay, Providenciales and either treated with one of the two treatments or kept as a control.

We are conducting a head-to-head trial of Coral Cure D versus amoxicillin in Base2B with a selection of control colonies left untreated. Although ongoing, we were able to revisit the site with up to three weeks since treatment and the results are positive! Soon we will be reporting on our experimental trials to help continue improving the product. Not only are we looking at efficacy compared to the amoxicillin treatment, we are also making observations on ease of application as well as other properties such as the swelling capabilities of the product which affect how deep into the grooves of certain corals the product can reach. If the treatment doesn’t reach down into the valleys of a brain coral, for example, it is less likely to be successful is stopping the disease progression.  

If you see a tagged coral, photograph it and email to SCTLD@tcreef.org.

We will be monitoring the treated coral heads and documenting each tagged colony photographically every two weeks (weather dependant) for two months and then once a month after that for a total of six months from treatment day. We will be looking at the comparative efficacy of this new treatment approach to that of the current standard of care, the amoxicillin in Base 2B. As mentioned above, preliminary observations are positive and if this treatment proves successful, it will be ground-breaking in SCTLD interventions. Even those most in favour of antibiotic intervention do so with a “time is of the essence” motivation. If a successful alternative can be found, this will ease environmental fears as well as probably easing permitting difficulties across the region and allowing strike teams to act faster. 

Is this a new hope? Well, I sure hope so! If you are interested in learning more about Stony Coral Tissue Loss Disease log onto https://www.agrra.org/coral-disease-outbreak/ and email alizee@tcreef.org. There are many ways in which we can all help the fight.