Abstract Summary
Presently, one of the most widespread and virulent coral disease outbreaks on record is affecting the Florida Reef Tract (FRT), resulting in the mortality of thousands of colonies of at least 20 species of scleractinian coral, including the primary reef building species. First reported near Key Biscayne FL during 2014, this outbreak, recently described as “Scleractinian Tissue-Loss Disease” (TLD), progressed southward along the FRT and by December 2017 had reached the middle Florida Keys. In January 2018, we established experimental “sentinel” plots in the middle Florida Keys that were disease-free, but just south of affected areas, to monitor the disease’s spatial progression, assess size and species-specific disease susceptibility and progression rates, and evaluate its small-scale spatial epidemiology. We established two plots each at four locations ranging from 25m2 to 100m2 in area and in each, measured and mapped the location of each coral colony. In all, we identified and monitored more than 1,350 coral colonies representing 23 species. At two-week intervals, each colony was assessed for the presence of disease and, if diseased, estimated the percentage of the colony affected. TLD was first observed during February 2018 and by March was evident at all sites. Among those species that were sufficiently abundant, a species-specific pattern was evident. M. meandrites initially exhibited the highest prevalence, followed by Dichocoenia stokesii, Colpophyllia natans, and Pseudodiploria strigosa, then followed by Orbicella faveolata and Montastraea cavernosa. No size-specificity in the rate of disease occurrence was evident across the species examined. Additionally, preliminary analyses revealed that coral colonies were randomly distributed at seven of the eight experimental plots, but no intra- or inter-specific spatial patterns in disease progression were evident. We are currently refining this analysis to incorporate possible temporal dynamics, but presently it appears that the spatial dynamics of TLD is occurring at a scale larger than our experimental plots.
