New Major Disease Strikes St. Thomas Corals Special contribution from Joseph Townsend, [email protected] Abstract A wide-sweeping new coral disease has appeared, is spreading throughout coral reef communities in southwestern St. Thomas and has researchers and managers working frantically to understand and contain the disease. Report In January of 2019, divers and swimmers noticed something strange at Flat Cay and just off of the St. Thomas airport runway. Based on the reports, researchers at the Center for Marine and Environmental Science at the University of the Virgin Islands decided to investigate and discovered a new coral disease was taking hold of the reefs of the Virgin Islands. The disease, which rapidly kills off coral tissue and leaves large portions of exposed white skeleton, appears to be the same or very similar to a coral disease currently ravaging the Florida Keys, identified there as Stony Coral Tissue Loss Disease (SCTLD). In Florida, SCTLD was first identified in 2014 following a dredging project in the Port of Miami (Precht et al. 2016), and has since rapidly spread throughout the entire Florida reef tract, an impressive 700 square mile-span in a matter of 5 years (Neely 2018; Brandt, personal communication). “The USVI has faced disastrous coral disease outbreaks before” says Leslie Henderson, the Coral Reef Initiative Coordinator for the VI Department of Planning and Natural Resources, “This new disease outbreak is different because it is attacking a wider range of species…[the] disease is also moving faster and kills entire colonies, leaving nothing behind to regrow.” Maze corals (Meandrina meandrites), brain corals (Pseudodiploria strigosa, Pseudodiplora clivosa, Diploria labyrinthiformis, Colpophyllia natans), and pillar corals (Dendrogyra cylindrus) have all been identified as particularly susceptible to this new disease in the VI. Once the disease is first identified on a reef however, it affects a wide range of species, including critical reef building star corals (Orbicella faveolata, Orbicella franksi, Orbicella annularis, Montastraea cavernosa, Solenastrea bournoni, Stephanocoenia intersepta) and starlet corals (Siderastrea siderea, Siderastrea radians) (Coral Disease Identification, 2018). Progression of the disease at the onset is rapid, many colonies experience complete mortality in a matter of days to weeks, depending on the size. Unfortunately, in both Florida and now in the USVI, a causative agent or pathogen for the disease is still unknown, making it difficult to combat, and it is still unclear how the disease spreads from reef to reef, though researchers suspect it is possibly able to travel through the water short distances on currents (Muller, van Woesik, & Sartor, 2018). Until the cause can be identified (and confirmed as a match with the disease in Florida), an effective treatment or cure won’t be able to be developed. In the meantime, researchers are removing diseased corals from reefs where it isn’t yet fully established, hopefully slowing the progression somewhat. Henderson also mentioned that both the University and DPNR are in the process of putting together a “strike team” to conduct this disease removal on a larger scale. While the disease won’t be able to be eradicated this way, containing the disease to its current expanse can buy time while more effective treatment can be developed. Additionally, researchers and managers are requesting that divers and swimmers do a complete decontamination of any equipment after visiting an area with disease by using a mild bleach solution (0.1%, or 1/3 cup of household bleach per gallon of fresh rinse water). To learn more about the disease outbreak, the research being done, and ongoing conservation efforts, visit DPNR’s webpage (www.vi.gov/czm/sctld) or the University’s webpage (www.viepscor.org/sctld).

Just off of the airport runway, Stony Coral Tissue Loss Disease is devastating the reef there. Once contracted, corals will develop large “lesions” of exposed white skeleton until all of the tissue has been removed and the coral is completely dead. Photo by Joseph Townsend, 2019.

Map of Saint Thomas with observation points where disease has been identified as severe (red), moderate (yellow), or absent (green), with the point of first observation at Flat Cay indicated with a star. The disease at the moment seems largely contained within the south western waters of St. Thomas, but has been slowly expanding westward, following prevailing currents. There have been no observations of the new disease on St. John or St. Croix. (Created by Joseph Townsend, based on Google Earth, last updated 7/24/2019) Works Cited Coral Disease Identification. (2018, October 2). Retrieved July 1, 2019, from http://www.agrra.org/coral-disease-identification/ Muller, E., van Woesik, R., and Sartor, C. 2018. Spatial Epidemiology Modeling of the Florida Coral Disease Outbreak. Florida DEP. Miami FL. pp. 1-20 Neely, K. 2018. Surveying the Florida Keys Southern Coral Disease Boundary. Florida DEP. Miami, FL. pp. 1-15 Precht, W. F., Gintert, B. E., Robbart, M. I., Fura, R., and van Woesik, R. (2016). Unprecedented disease-related coral mortality in Southeastern Florida. Scientific Reports 6: 31374