Abstract
For the last 7 years, Florida’s Coral Reef (FCR) has suffered from widespread and severe coral loss caused by stony coral tissue loss disease (SCTLD). First observed off the coast of Miami-Dade county in 2014, the outbreak has since spread throughout the entirety of FCR and some areas of the Caribbean. However, the propagation of the disease through FCR seemed to slow down when it reached the western end of the Marquesas in August 2020. Despite being present about 30 km (∼20 miles) from the Dry Tortugas (DRTO), SCTLD was not reported in this area before May 2021. As SCTLD transmission is likely to be waterborne, here we suggest that this apparently delayed propagation is related to eddy activity near the DRTO under the influence of the Loop Current/Florida Current system. To quantify the impact of the local ocean circulation on the spread of SCTLD from the Marquesas and the DRTO, we evaluated the hydrodynamic-predicted connectivity between these two regions using a high-resolution hydro-epidemiological model between May 2018 and May 2021. Our results suggest that the Marquesas and the DRTO were not connected during February-October 2020 and January-May 2021. These periods coincided with either the occurrence of Tortugas gyres and mean circulation with an eastward component between the Marquesas and the DRTO or the presence of southward currents. Our results suggest that disease agents probably reached the DRTO in November 2020 and that they most likely originated from southern or northwestern reefs of the Marquesas. This study provides novel insight into the role played by the hydrodynamics in the spread of SCTLD within the western-most edge of FCR, and in propagating the disease to uninfected locations.
Highlights
Over the last 7 years, Florida’s Coral Reef (FCR) has suffered from a widespread decline in living, reef-building corals due to a multi-year coral-disease outbreak (Precht et al, 2016; Walton et al, 2018), called stony coral tissue loss disease (SCTLD)
Stony Coral Tissue Loss Disease data was obtained by using the Florida Reef Resilience Program’s Disturbance Response Monitoring Report for 2019 and 2020 (FRRP, 2019, 2020) as well as the Atlantic and Gulf Rapid Reef Assessment (AGGRA) resources for SCTLD reported throughout the Caribbean, an open access spatial and temporal database curated by experts in Caribbean coral reef ecology1 (Kramer et al, 2019)
Assumptions associated with SCTLD included the following: (i) SCTLD is different from other tissue loss diseases previously reported on corals based on its ecology and case definition (NOAA, 2018), (ii) SCTLD is transmitted, in part, by ocean currents (Aeby et al, 2019; Muller et al, 2020; Eaton et al, 2021) and (iii) SCTLD was along the western most reef area of the Lower Florida Keys in October 2019, reached the western most part of the Marquesas in August 2020, and did not occur in Dry Tortugas (DRTO) until May 2021 based on curated data provided by the FRRP reports and the AGGRA open access database
Summary
Over the last 7 years, Florida’s Coral Reef (FCR) has suffered from a widespread decline in living, reef-building corals due to a multi-year coral-disease outbreak (Precht et al, 2016; Walton et al, 2018), called stony coral tissue loss disease (SCTLD). SCTLD was observed propagating faster than 100 m/day within the Marquesas between October 2019 and August 2020 and would have reached the reefs of the Dry Tortugas (DRTO) by February 2021 if it had spread at a high propagation rate (Kramer et al, 2019). These propagation rates were observed in a relatively dense shallowwater reef system and mostly occurred through transmission from neighbor to neighbor. Questions remain about the timing of the spread of the disease to the DRTO as well as the role played by hydrodynamics in the process
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