2015-2016 Coral Disease Outbreak in Florida
The FWRI corals research section investigates coral mortality events which occur along the Florida Reef Tract. In 2015 and 2016, numerous reports of coral disease outbreaks in Southeast Florida, the Upper Florida Keys and the Dry Tortugas National Park. This ongoing event is one of the largest coral disease outbreaks in recent decades.
Coral reefs are fragile ecosystems that support a plethora of marine life and provide critical resources to sustain many important fisheries. Coral reefs grow slowly over millions of years and are created by slow-growing corals that deposit limestone skeletons making up the structure of a coral reef. These large physical barriers protect our coastlines from erosion. They are subjected to many anthropogenic (human-caused) and natural stressors. With increasing human populations in desirable coastal locations, chronic disturbances have taken their toll on the marine environment. Anthropogenic stressors include coastal construction activities (i.e., coastal development, dredging activities), pollution, land-based runoff (i.e., sedimentation and nutrients), overfishing, and physical damage from ship groundings, cable and anchor drags. A prime example of these chronically impacted marine areas is the Southeast Florida region which has two major shipping ports, regular coastal construction activities, and a continually growing human population. Compounding these anthropogenic stressors are natural stressors which can be abiotic (nonbiological) or biotic (biological) in nature. Abiotic factors include rising sea-surface temperatures and temperature anomalies, UV radiation, and physical damage from hurricanes. Biological factors include predation, bioerosion and diseases caused by bacteria, cyanobacteria, viruses, fungi, ciliates, and parasites. The first reports of coral disease in the Florida Keys and Caribbean emerged in the 1970s. Since that time, worldwide reports have been increasing in frequency. Coral disease is now recognized as a major cause of reef-building coral mortality and reef degradation. From spring 2015 to present, coral disease outbreaks, which are greater than natural background disease levels, have been reported to affect corals offshore Southeast Florida, within the Upper Keys, and Dry Tortugas National Park.
During the Coral Reef Evaluation and Monitoring Project (CREMP) annual survey effort at Grecian Rocks in the Upper Keys in July 2016, the team observed what appeared to be multiple diseases on at least 11 species of scleractinian coral. Species affected include: Colpophyllia natans (Figure 1), Pseudodiploria strigosa, Diploria labyrinthiformis (Figure 2), Meandrina meandrites, Dichocoenia stokesii, Siderastrea siderea, Montastraea cavernosa, Orbicella annularis, Eusmilia fastigiata, Undaria agaricites, and Porites astreoides. The diseases observed include what appeared to be white plague, the unknown white disease that is being called “white blotch”, and other indistinguishable white diseases. The CREMP team spent time at the end of the dive to take photographs of affected colonies and prepared a summary report of the outbreak. The following week, the CREMP team sampled colonies affected with the unknown white blotch disease at the affected site and conducted prevalence surveys (which document the amount of coral colonies of the population affected by disease). For tissue sampling, four species were targeted including M. cavernosa, S. siderea, C. natans and D. labyrinthiformis for histopathology and molecular samples. Prevalence surveys (11, 10mx1m belt transects) revealed that 100% of M. meandrites colonies, 66.7% of D. labyrinthiformis colonies, 53.3% of M. cavernosacolonies, 50% of D. stokesii colonies, 50% of P. strigosa colonies, 42.3% of S. siderea colonies, 33.3% of C. natans colonies, and 33.3% of E. fastigiata colonies were actively diseased or recently dead. An investigation is ongoing to determine the cause of the unknown disease.
Left: Large Colpophyllia natans colony at Grecian Rocks photographed in 2012; Right: Same Colpophyllia natans colony photographed with active unknown “white blotch” disease lesions 7/16/2016.
Left: Large Diploria labyrinthiformis colony at Grecian Rocks photographed in 2015; Right: Same Diploria labyrinthiformis colony with active unknown “white blotch” disease lesions photographed on 7/16/2016.