by Vanessa Brinkhuis
Coral disease is recognized as a major cause of reef-building coral mortality and reef degradation. The first reports of coral disease in the Florida Keys and Caribbean emerged in the 1970’s. Since that time, worldwide reports have been increasing in frequency. From spring 2015 to present, coral disease outbreaks, which are greater than natural background disease levels, have been reported offshore Southeast Florida, within the Upper Keys and Dry Tortugas National Park. Initial reports in 2015 indicated disease outbreaks were occurring offshore Miami-Dade County. Since those initial reports, further disease outbreaks are being reported in areas north and south of the initial outbreak area.
During the Coral Reef Evaluation and Monitoring Project (CREMP)’s 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 (Figure 2), Diploria labyrinthiformis, Meandrina meandrites, Dichocoenia stokesii (Figure 3), Siderastrea siderea (Figure 1), Montastraea cavernosa, Orbicella annularis, Eusmilia fastigiata, Undaria agaricites and Porites astreoides. The diseases observed include what appear to be White Plague (Figures 2 and 3), the unknown white disease that is being called “White Blotch” (Figures 1 and 4), and other indistinguishable white diseases. The CREMP team photographed affected colonies and prepared a summary report of the outbreak.
The following week, the CREMP team sampled coral 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. cavernosa colonies, 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 extent and etiology of the disease outbreak.