Corals--Diseases

Since the emergence of stony coral tissue loss disease (SCTLD) in 2014, 60% of live coral cover on Florida’s coral reefs have been lost. This study assessed the efficacy of outplanting microfragment colony arrays of three SCTLD-susceptible coral species (Montastraea cavernosa, Orbicella faveolata, and Pseudodiploria clivosa) as remediation technique in two SCTLD-degraded reef areas, St. Lucie Reef and Palm Beach, in southeast Florida. After approximately 2 years, outplanted colonies at both reefs experienced ≥ 75 % survivorship, net positive growth rates, and fragment fusion, with some variation between species and across reefs. Additionally, outplanting SCTLD-susceptible species did not increase local disease prevalence and resulted in low disease prevalence on the outplanted colonies. The results from this study will be used to inform and optimize ongoing and future outplanting based coral restoration projects throughout Florida’s coral reefs and the wider Caribbean.

Stony coral tissue loss disease (SCTLD) emerged in 2014 and has since spread across Florida’s Coral Reef (FCR) and the Caribbean. This thesis is part of a larger project assessing the efficacy of restoring SCTLD-susceptible corals Montastraea cavernosa, Orbicella faveolata, and Pseudodiploria clivosa in SCTLD endemic areas. As part of Florida’s largest coral restoration experiment to date, 1,152 cement bases with 5,760 coral fragments from 99 source colonies were outplanted across six regions throughout FCR and monitored monthly over two years for survival, disease, and growth. Before outplanting, coral tissue samples were collected for high-resolution 2bRAD and ITS2 sequencing to genotype the corals and characterize their initial algal symbiont communities. Neither host genetic lineages nor algal symbiont types significantly affected SCTLD susceptibility or survival, negating the hypothesis of SCTLD-resistant “super coral” lineages. Results from this study will inform the feasibility and design of future coral restoration efforts in SCTLD endemic zones to maintain or enhance coral biodiversity.

Florida’s coral reefs are facing a multi-year coral disease outbreak described as stony coral tissue loss disease (SCTLD), affecting at least 24 species of scleractinian corals. Potential anthropogenic and environmental drivers of SCTLD progression and severity are still poorly understood. This project was designed to determine the potential impacts of elevated nutrients on the progression and spread of SCTLD on reefs in Southeast Florida. We attempted to increase nutrient levels near coral colonies using fertilizer amendments to mimic the effects of agricultural and urban runoff. SCTLD lesion progression, coral tissue loss, and disease prevalence were tracked overtime. There were no significant differences in nutrient concentrations between nutrient-amended and control groups or SCTLD progressions or surrounding SCTLD prevalence. However, water temperature was positively correlated to SCTLD activity. These findings provide insight to reef managers seeking to limit and mitigate the prevalence and impacts of SCTLD.

Stony coral tissue loss disease (SCTLD) has spread throughout the entirety of Florida’s Coral Reef (FCR) and across the Caribbean, impacting over 50 coral species. The threatened hermatypic coral, Orbicella faveolata, demonstrates intraspecific variation in SCTLD resistance and has been categorized into three resistance levels: “High”, “Medium”, and “Low”. This study evaluated potential genomic underpinnings of variable disease susceptibility by monitoring and sampling 90 O. faveolata colonies from Southeast Florida and the Lower Keys. High resolution analyses of >11,000 single nucleotide polymorphisms identified no significant genetic lineages among O. faveolata colonies associated with SCTLD resistance or susceptibility. Algal symbiont community analysis revealed that Durusdinium was present in greater abundances in SCTLD-affected colonies compared to the “High” resistance group, suggesting that algal symbiont community structure may play a role in SCTLD resistance. Data generated by this research will be combined with complementary approaches to further investigate the complex drivers of SCTLD resilience.

Stony coral tissue loss disease (SCTLD) has been spreading throughout Caribbean coral reefs since 2014, heavily impacting scleractinian corals. To mitigate losses, this experiment assessed the effectiveness of two SCTLD intervention treatments in situ. SCTLD-affected Montastraea cavernosa colonies offshore of Broward County were divided into three treatment groups: 1) chlorinated epoxy, 2) Base 2B plus amoxicillin, and 3) untreated controls, plus a fourth group of healthy untreated controls. These colonies were monitored over 11 months to record SCTLD status, lesion activity, colony mortality, and changes in healthy tissue area with 3D modelling. The Base 2B plus amoxicillin treatment was more effective at halting SCTLD lesions, slowing the rate of tissue loss, and decreasing the overall proportion of tissue lost as compared to chlorinated epoxy or no treatment. However, neither treatment prevented new SCTLD lesions from developing. These findings can enhance the effectiveness of Caribbean management efforts to mitigate SCTLD impacts.

Since 2014 stony coral tissue loss disease (SCTLD) has contributed substantially to declines of reef-building corals in Florida. Monthly surveys were conducted throughout the northern Florida reef tract to monitor the spread and impacts of SCTLD on a larger spatial scale. SCTLD disease prevalence was lower in Palm Beach County than in Broward or Martin County, but there were no significant changes in prevalence over time. To assess colony level impacts of the disease, this study optimized a 3D photogrammetry technique for fate-tracking infected Montastraea cavernosa coral colonies with a low-cost, rapid protocol that measured tissue area over three time points. Total colony area and healthy tissue area decreased significantly over time, while disease area did not significantly vary. Traditional coral surveys combined with the 3D photogrammetry method provide greater insights into the spatial/temporal dynamics and impacts of this disease on individual corals and reef populations than surveys alone.