Multi-Variate Analyses of Coral Mortality From the 2014–2015 Stony Coral Tissue Loss Disease Outbreak Off Miami-Dade County, Florida

Abstract

Environmental compliance monitoring associated with the Port Miami dredging project (2013–2015), designed to assess the impact of project-generated sediments on the local coral community, fortuitously captured a thermal bleaching event and the first reports of an emergent, highly contagious, white-plague-like coral disease outbreak in the fall of 2014. The disease, now termed stony coral tissue loss disease (SCTLD), has decimated reefs throughout Florida and is now spreading across the Caribbean. The high prevalence of disease, the number of affected species, and the high mortality of corals affected suggests SCTLD may be the most lethal coral disease ever recorded. Previous analyses of the dredge monitoring data have reached mixed conclusions about the relative impact of dredging on coral mortality and has often parsed out disease susceptible individuals to isolate the impacts of dredging only. We use multi-variate analyses, including time-based survival analyses, to examine the timing and impacts of dredging, coral bleaching, and disease on local coral mortality. By examining the status of corals monthly from the October 2013 to July 2015 observational period, we found that coral mortality was not significantly affected by a coral’s proximity to the dredge site or sediment burial. Instead, coral mortality was most strongly impacted by disease and the emergence of SCTLD during the monitoring period. During the 2-year monitoring period, 26.3% of the monitored corals died, but the only conditions significantly affected by the dredge were partial burial and partial mortality. The strongest link to mortality was due to disease, which impacted coral species differently depending on their susceptibility to SCTLD. The focus on disturbances associated with dredging created a circumstance where the greater impacts of this emergent disease were downplayed, leading to a false narrative of the resulting mortality on the local coral communities. The results of this study reveal that while local events such as a dredging project do have quantifiable effects and can be harmful to corals, regional and global threats that result in mass coral mortality such as thermal stress and disease represent an existential threat to coral reefs and must be urgently addressed.

Reef Sediments Can Act As a Stony Coral Tissue Loss Disease Vector

“…First observed in 2014 off Virginia Key in Miami-Dade County, Florida, stony coral tissue loss disease (SCTLD) has become perhaps the most damaging described coral disease to date (Walton et al, 2018;Gintert et al, 2019;Spadafore et al, 2021). Since then, it has spread throughout the entirety of Florida's Coral Reef, notably reaching the Dry Tortugas in 2021 (NOAA, 2018;Dobbelaere et al, 2020b;Muller et al, 2020;Roth et al, 2020;Sharp et al, 2020), and has now been observed in a growing number of Caribbean territories (Alvarez-Filip et al, 2019;Meiling et al, 2020;Roth et al, 2020;Dahlgren et al, 2021;Estrada-Saldívar et al, 2021;Heres et al, 2021).…”

“…Dredging operations in southeast Florida, such as the Port of Miami expansion that occurred in 2013-2015, can cause the release of sediments onto local coral reef habitats (Walker et al, 2012;Miller et al, 2016;Cunning et al, 2019), which can lead to smothering of colonies in extreme cases, as well as sedimentation-associated stress and mortality (Vargas-Ángel et al, 2006(Vargas-Ángel et al, , 2007Erftemeijer et al, 2012;Shore-Maggio et al, 2018). While it is difficult to disentangle coral mortality due to sedimentation, SCTLD, or a prior thermal stress event, several studies suggest that sedimentation played a role in sublethal and lethal effects on local coral populations due to the dredging of Port of Miami (Miller et al, 2016;Cunning et al, 2019;Gintert et al, 2019;Spadafore et al, 2021). Additionally, the plume was observed through remote sensing platforms over an estimated 228 km 2 in southeast Florida (Barnes et al, 2015), suggesting the potential for spread of the pathogen(s) through local currents and sediment transport to northward reefs, including potential interactive effects of sedimentation on coral health (Dobbelaere et al, 2020a,b).…”

Effect of species, size, and chimerism on the susceptibility of Caribbean brain coral recruits to stony coral tissue loss disease (SCTLD)

“…It has spread rapidly throughout Florida’s Coral Reef and beyond, resulting in extremely high rates of infection and mortality at affected sites (Precht et al, 2016; Walton et al, 2018; FKNMS, 2018; Alvarez-Filip et al, 2019; Sharp et al, 2020; Dahlgren et al, 2021; Brandt et al, 2021). Localized outbreaks have precipitated significant declines in live coral tissue area (>60%) over short periods of time (Walton et al, 2018; Sharp et al, 2020; Heres et al, 2021; Brandt et al, 2021), with some species being more severely impacted than others (Gintert et al, 2019; Costa et al, 2021; Neely et al, 2021a; Spadafore et al, 2021). In surveys in Miami-Dade county in 2015 and 2016, Precht et al (2016) documented 83% infection in Diploria labyrinthiformis colonies, and estimated that these populations were reduced to <25% of their original numbers.…”

Chemical and genomic characterization of a potential probiotic treatment for stony coral tissue loss disease

“…O ver 20 species of corals along Florida's coral reef have been affected by an ongoing mass mortality event resulting in significant losses of various coral species (1)(2)(3)(4)(5). These mortalities are attributed to a waterborne disease with unknown etiology called stony coral tissue loss disease (SCTLD), which has been continuously spreading since its first observation in 2014 1 .…”

“…This outbreak of SCTLD represents one of the many "local" threats Florida's coral reefs face that must be mitigated to prevent catastrophic losses driven by global threats like climate change 2 . The SCTLD outbreak has already negatively impacted coral reef ecosystems in Florida 3,4 , so additional local or global threats only further push these reefs past recovery. Unfortunately, by 2018, SCTLD had reached reefs around Mexico 5 , and as of December 2022, at least 26 different Caribbean countries/territories are reporting signs of this disease (https:// www.agrra.org/coral-disease-outbreak/).…”