Abstract
Since 2014, stony coral tissue loss disease (SCTLD) has led to large-scale mortality of over 20 coral species throughout the Florida Reef Tract. In 2019, in-water disease intervention strategies were implemented to treat affected corals. Two treatment strategies were employed: (1) topical application of an amoxicillin paste directly to disease margins, and (2) application of a chlorinated epoxy to disease margins as well as an adjacent “disease break” trench. Effectiveness of treatments on 2,379 lesions from 725 corals representing five species was evaluated using mixed effects logistic regression models which demonstrated substantially greater effectiveness of amoxicillin compared to chlorine-treated lesions across all species up to 3 months post-treatment. As a result of the failed chlorinated epoxy treatments, any new lesions that appeared during subsequent monitoring events were treated with amoxicillin paste, and all corals were monitored and treated as needed approximately every 2 months for up to 24 months. The health status of 1664 amoxicillin-treated corals during each monitoring event was used to model the probability of a coral being uninfected over time. Models included species and geographic regions as variables. The appearance of new lesions (reinfection rates) varied by species, and offshore sites showed greater reinfection rates than inshore sites; however, all sites and species exhibited a decreased probability of reinfection with time since initial treatment. We conclude that topical amoxicillin treatments are highly effective at halting SCTLD lesions and that through initial and follow-up treatments as needed, colonies and reef sites will progress toward a lower prevalence of SCTLD.
Highlights
Coral diseases are found on reefs throughout the world and are one of the most rapid and prevalent sources of coral mortality, even among the myriad stressors that are driving the decline of reefs
The best-approximating mixed effects logistic regression model assessing the probability of successful lesion treatment included number of days since treatment, treatment type, region, species, number of days since treatment × treatment type, region × treatment type, and species × treatment type
The goodness of fit assessments based on scaled residuals indicated that all candidate logistic regression models provided an adequate fit to the data
Summary
Coral diseases are found on reefs throughout the world and are one of the most rapid and prevalent sources of coral mortality, even among the myriad stressors that are driving the decline of reefs. Diseases have been documented in over 100 coral species and over 50 different nations (Green and Bruckner, 2000; Bruckner, 2016). Even though disease is traditionally present in ecosystems, elevated prevalence and virulence has resulted in elevated “background” rates as well as increasingly common outbreaks that can affect coral cover and species diversity (Cróquer et al, 2005). Coral disease has led to substantial changes in reef communities, from localized declines in various species (Cróquer et al, 2005) to the widespread loss of over 90% of acroporid corals throughout the Caribbean (Aronson and Precht, 2001)
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