A high-resolution connectivity-based model for the spread of Stony Coral Tissue Loss Disease in the Florida Reef Tract
(2021) International Coral Reef Symposium (ICRS) 2021 — Location: Online (19.July.2021)
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- Abstract
- For about five years, the Florida Reef Tract (FRT) has been experiencing an outbreak of the Stony Coral Tissue Loss Disease (SCTLD). First reported off the coast of Miami-Dade County in 2014, the SCTLD outbreak now spans from the northern extent of the reef tract in Martin County down to Rock Key in the Lower Keys. However, the causative agent for this outbreak is currently unknown. One hypothesis is that it is transported within composite material (such as coral mucus, dying tissues and/or resuspended sediments) driven by currents and potentially persisting in the water column for extended periods of time. The oceanographic feasibility of this hypothesis has been tested with a three-state (Susceptible, Exposed, Infected) epidemiological model based on connectivity data obtained with the high-resolution, two-dimensional ocean model SLIM. SLIM locally achieves a spatial resolution of up to 100 m over the scale of the entire FRT, which allows us to simulate transport processes at the reef scale. Using forcing and boundary conditions for the period of August 2016 to February 2017 for this model, we investigated three transport modes for the disease causative agents: (i) negatively buoyant particles in the bottom boundary layer; (ii) neutrally buoyant particles in the water column; and (iii) positively buoyant particles in the near-surface layer. Model simulations combining each of these three transport modes with different biological/epidemiological parameters have been investigated in an attempt to reproduce the observed spread of the SCTLD throughout the FRT. Simulations using positively and neutrally buoyant materials as vectors propagate the disease too fast for most disease transmission parameters while negatively buoyant materials produce plausible disease propagation based on observations for every simulation performed. These results strongly suggests that bottom currents drive the propagation of the outbreak, although epidemiological parameters still need to be more precisely determined. Our modelling framework provides new tools for marine resource managers to identify the causative agent of SCTLD as well as to predict when the remaining healthy reefs will be hit. Our framework also allows for backward simulation in time and could therefore provide information on the source point(s) of the outbreak.
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Citations
Dobbelaere, T., Muller, E. M., Gramer, L. J., & Holstein, D. M. (2021). A high-resolution connectivity-based model for the spread of Stony Coral Tissue Loss Disease in the Florida Reef Tract. International Coral Reef Symposium (ICRS) 2021, Online. https://hdl.handle.net/2078.5/112761