Florida Reef Tract Coral Disease Outbreak: Response



Why it is difficult to determine a cause

Corals contain an assemblage of microbes and algae co-existing as a complex system, which makes the identification of disease pathogens an intricate task. Additionally, corals are in an open system – the ocean – with constant input of microbes from the environment, further complicating the investigative process.

Bacteria can be a primary pathogen, a secondary pathogen creating a secondary infection in unhealthy corals, or an opportunistic pathogen attacking corals with depressed immune function. Some of these pathogens may be normally associated with corals and are harmless until triggered by an environmental change. The relatively new scientific field of coral disease has identified only about a dozen pathogens in the world.

Current hypotheses include that secondary pathogens are influencing the virulence of stony coral tissue loss disease, while environmental factors may be affecting disease progression and transmission. Experiments are ongoing. The identification and isolate of the pathogen(s) causing stony coral tissue loss will be important for the development of diagnostic tools and more targeted treatments.

Pathogen Research

Research continues into finding the pathogen responsible for the stony coral tissue loss disease impacting the Florida Reef Tract. While the exact pathogen remains unknown, laboratory studies by Dr. Blake Ushijima of the Smithsonian Marine Station and field observations by coral ecologist Dr. Greta Aeby of the University of Qatar, suggest that multiple microorganisms may play a role. They think it is likely that an initial pathogen attacks the healthy coral and opportunistic pathogens then accelerate the disease. These infections appear as different lesions on the coral. The pathogen(s) is known to spread through direct coral-to-coral contact as well as through ocean currents. Dr. Ushijima continues to search for the pathogen and Dr. Aeby is examining other modes of possible infection.

Interventions and Treatments

Scientists and resource managers are coordinating interventions and treatments with the goal to slow or stop the spread of stony coral tissue loss disease. The most urgent needs are at the disease front in the Lower Keys. Strategies include colony-specific interventions to prevent mortality of the most important corals, efforts to reduce the pathogen load, and salvage of selected colonies to prevent the loss of the diversity and genetic structure of the corals.

Ballast Water Best Management Practices to reduce the likelihood of transporting pathogens that may spread stony coral tissue loss disease

At the request of NOAA, the United States Coast Guard is considering options to mitigate the potential factors that may be contributing to the spread of stony coral tissue loss disease including the potential transfer of pathogens in ballast water. Current federal regulations specify that certain ships conduct ballast water exchanges beyond 200 nautical miles of any shore prior to discharge of ballast water within U.S. waters. In additional, vessels are encouraged to use their existing ballast water management systems to treat ballast water prior to release. Outside of U.S. waters, unmanaged ballast water should not be released within either 12 nautical miles of any shore or water less than 200 meters in depth.

Coral Rescue

Coral Monitoring Dashboard

List of zoos and aquariums continues to expand

In December 2018, the Association of Zoos and Aquariums joined the collaborative response to stony coral tissue loss disease. As part of the newly-formed AZA-Florida Reef Tract Rescue Project, more than 20 facilities have agreed to hold susceptible coral colonies harvested from the Florida Keys and Dry Tortugas National Park for restoration purposes. The corals will be held in AZA facilities then brought back to Florida for breeding. The resulting offspring will increase the number of individuals and genetic diversity for restoration of Florida's reefs. Before the rescued corals travel outside of Florida, they are kept in intermediate holding facilities at The Florida Aquarium, Nova Southeastern University, the University of Miami, and Mote Marine Laboratory and Aquarium. A dozen AZA-member facilities outside of Florida are currently accepting or caring for rescued corals and more facilities will be joining the effort within the near future.

AZA Holding Facilities

Coral Rescue Photos

NSU Researchers Part of Ambitious Plan to Save Coral Reefs

The Florida Aquarium Conducts a Huge Multi-Agency Conservation Mission in Florida Keys to Help Restore Florida's Reefs

The Florida Aquarium Will Apply Coral Breeding Techniques to Disease-Affected Species to Replenish Diseased Reefs

Former military divers come to the aid of scientists combating coral disease

FORCE BLUE divers working with scientists from Nova Southeastern University completed a a 50 day dive mission to treat diseased coral colonies in the Florida Keys. Veterans with the nonprofit organization utilize their unique skills to apply antibiotic and chlorine treatments on diseased corals in the Florida Keys National Marine Sanctuary. The experimental treatments, funded by the Florida Department of Environmental Protection, aim to save priority coral colonies and provide scientific insight into stony coral tissue loss disease. As a bonus, the work also provides former combat divers with a new mission – saving Florida's coral reefs.

Project Protect - Stony Coral Tissue Loss Disease Interdiction

Assessing effectiveness of treatments

A team of scientists out of Nova Southeastern University lead by Brian Walker, have been assessing and treating coral disease of the 60 largest, healthiest corals from Pompano Beach to Key Biscayne. After one year of monthly monitoring, it appears that there could be some periodicity of new disease infections. The number of required treatments varied by month. The highest number of treatments were in June, right after the onset of the rainy season (May) and rose again in August and September, the warmest water periods. The number of new treatments has steadily dropped since early 2019. Also, the number of newly infected colonies followed a similar pattern with the highest number of newly infected large corals in May and August. There have been no newly infected large corals since November 2018, leaving 22 large monitored corals that have resisted infection to date.

before and after view of a treated coral
An identified disease lesion on a Star Coral (Orbicella faviolata) was treated in August 2018 during monthly monitoring surveys. Six months later, the treatment showed to have halted the progression of the disease. Photo: Alysha Brunelle/NSU

Probiotic Experiments

Scientists are testing the theory that probiotics may bolster coral resistance and recovery. Researchers with the Smithsonian and the University of Florida are using healthy corals taken from Florida waters to develop probiotics that could slow or prevent disease progression. They isolate potentially beneficial microorganisms (probiotics) from more disease-resistant coral genotypes and test them on great star coral (Montastraea cavernosa), one of the species susceptible to stony coral tissue loss disease.

Preliminary results suggest that these good bacteria on healthy corals may help defend their host from infection and that they are a plausible treatment for diseased corals. Additional experiments suggest that the beneficial effects of probiotic treatments may be transferrable from probiotic-treated healthy corals to diseased corals, potentially allowing for simultaneous restoration and treatment efforts. The next steps are to optimize treatments and develop delivery methods. Probiotic treatments could have the potential to colonize corals and provide a more lasting protection, which would be immensely valuable to disease management efforts.

Disease intervention strategies to save Florida's largest, oldest corals

Nova Southeastern University laboratory treatment trials in tanks

Nova Southeastern University laboratory treatment trials in ocean

Direct UV treatment unsuccessful at halting disease progression


Diver Alysha Brunelle applies chlorinated epoxy to the firebreak and active disease margins on a Great Star coral (Montastraea cavernosa) as an experiment to determine if it will slow or stop progression of stony coral tissue loss disease. Credit: Brian K. Walker/Nova Southeastern University. Higher Resolution Version

Additional videos and photos

Researcher Brian Walker uses the hammer and chisel method to create a 1-2 cm wide and 1 cm deep firebreak along the scored marks around a disease margin. Credit: Alysha Brunelle/Nova Southeastern University. Higher Resolution Version

Additional videos and photos


Mission: Iconic Reefs

In response to the decline in coral reef health, the Florida Keys region has become a world leader in coral reef restoration. Although local efforts have had success at small scales, restoration has not been able to keep up with the rate of decline. Using the best available restoration science, NOAA and partners will restore diverse, reef-building corals at seven reef sites within Florida Keys National Marine Sanctuary that represent the iconic diversity and productivity of Florida Keys coral reefs. For the first time, NOAA will proactively intervene with natural conditions by removing nuisance and invasive species and introducing disease-resistant and climate-resilient corals.

A map highlighting the seven reefs in the Florida Keys targeted by Mission: Iconic Reefs

Disease-resistant corals are being studied for restoration efforts. In laboratories throughout Florida, gene banks preserve species that could potentially be grown and transplanted along the reef.

Coral Rescue – Healthy corals of the susceptible species collected and stored in land-based facilities to maintain diversity in restoration projects.

Mote Marine Laboratory expands restoration efforts

Pillar Coral Genetic Rescue Project

Mote Marine Laboratory on Summerland Key developed a micro-fragmentation and fusion method to speed the growth of brain, boulder and star corals - crucial reef-building species known for their slow growth in the wild.


scientist handeling coral fragments in a water tank
Mote Marine Laboratory on Summerland Key developed a micro-fragmentation and fusion method to speed the growth of crucial reef-building species. Credit: Mote Marine Laboratory