Environmental and human drivers of stony coral tissue loss disease (SCTLD) incidence within the Southeast Florida Coral Reef Ecosystem Conservation Area Final Report

This report describes an effort to test whether there are predictable patterns of SCTLD incidence within a population of largest colonies being monitored monthly and treated when necessary. Several predictor variables hypothesized to be linked to SCTLD incidence were synthesized. These included abiotic environmental drivers (e.g., depth, seawater temperature, seawater nutrient concentrations) and human drivers (e.g., density of septic tanks as a proxy for human coastal development), outflow from the Inlet Contributing Areas (ICAs), and distance to offshore outfall locations). We calculated colony-specific estimates of these predictor variables and built statistical models to test their ability to explain spatial and temporal patterns in SCTLD infections. The temporal model explained 56.4% of the temporal variation in the total number of SCTLD infections over time. SCTLD infections showed a positive correlation with temperature stress, inlet flow, and total rainfall.  The spatial model explained 38.0% of the spatial variation in the total number of SCTLD infections over the entire period. SCTLD infections showed a positive correlation with the number of septic tanks within a 5 km radius, with a noticeable increase in lesions occurring beyond ~100 tanks. The correlation with the distance to the Government Cut outfall was less clear, with the number of lesions maximized at mid-distances.

These investigations showed that coastal urbanization and water management influence the number of coral disease lesions on Florida’s Coral Reef within the Coral ECA. They suggest strong links between SCTLD infection levels and potential pollutants, or pathogens associated with the presence of anthropogenically impacted water flowing out of the inlets. The nature and extent of these links warrant urgent and immediate attention.