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1. Microbial dysbiosis reflects disease resistance in diverse coral species

   https://doi.org/10.1038/s42003-021-02163-5  

   MacKnight, Nicholas J.; Cobleigh, Kathryn; Lasseigne, Danielle; Chaves-Fonnegra, Andia; Gutting, Alexandra; Dimos, Bradford; Antoine, Jendahye; Fuess, Lauren; Ricci, Contessa; Butler, Caleb; et al (December 2021, Communications Biology)

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   Abstract Disease outbreaks have caused significant declines of keystone coral species. While forecasting disease outbreaks based on environmental factors has progressed, we still lack a comparative understanding of susceptibility among coral species that would help predict disease impacts on coral communities. The present study compared the phenotypic and microbial responses of seven Caribbean coral species with diverse life-history strategies after exposure to white plague disease. Disease incidence and lesion progression rates were evaluated over a seven-day exposure. Coral microbiomes were sampled after lesion appearance or at the end of the experiment if no disease signs appeared. A spectrum of disease susceptibility was observed among the coral species that corresponded to microbial dysbiosis. This dysbiosis promotes greater disease susceptiblity in coral perhaps through different tolerant thresholds for change in the microbiome. The different disease susceptibility can affect coral’s ecological function and ultimately shape reef ecosystems. 

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2. Deciphering Coral Disease Dynamics: Integrating Host, Microbiome, and the Changing Environment

   https://doi.org/10.3389/fevo.2020.575927  

   Vega Thurber, Rebecca; Mydlarz, Laura D.; Brandt, Marilyn; Harvell, Drew; Weil, Ernesto; Raymundo, Laurie; Willis, Bette L.; Langevin, Stan; Tracy, Allison M.; Littman, Raechel; et al (November 2020, Frontiers in Ecology and Evolution)

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   Diseases of tropical reef organisms is an intensive area of study, but despite significant advances in methodology and the global knowledge base, identifying the proximate causes of disease outbreaks remains difficult. The dynamics of infectious wildlife diseases are known to be influenced by shifting interactions among the host, pathogen, and other members of the microbiome, and a collective body of work clearly demonstrates that this is also the case for the main foundation species on reefs, corals. Yet, among wildlife, outbreaks of coral diseases stand out as being driven largely by a changing environment. These outbreaks contributed not only to significant losses of coral species but also to whole ecosystem regime shifts. Here we suggest that to better decipher the disease dynamics of corals, we must integrate more holistic and modern paradigms that consider multiple and variable interactions among the three major players in epizootics: the host, its associated microbiome, and the environment. In this perspective, we discuss how expanding the pathogen component of the classic host-pathogen-environment disease triad to incorporate shifts in the microbiome leading to dysbiosis provides a better model for understanding coral disease dynamics. We outline and discuss issues arising when evaluating each component of this trio and make suggestions for bridging gaps between them. We further suggest that to best tackle these challenges, researchers must adjust standard paradigms, like the classic one pathogen-one disease model, that, to date, have been ineffectual at uncovering many of the emergent properties of coral reef disease dynamics. Lastly, we make recommendations for ways forward in the fields of marine disease ecology and the future of coral reef conservation and restoration given these observations. 

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3. Ineffectiveness of topical antibiotics in treating Acropora spp. affected by white diseases

   https://doi.org/10.3389/fmars.2025.1720360  

   Coble, Avery; Meiling, Sonora; Smith, Tyler B; Brandt, Marilyn (January 2026, Frontiers in Marine Science)

   For many decades, white band disease (WB) and white pox disease (WPX) have been severely impacting populations of the reef building coralsAcropora palmataandA. cervicornisthroughout the Caribbean region. Even after the major outbreaks in the 1990s and early 2000s, these diseases still occur annually in certain regions of the Caribbean, including in the United States Virgin Islands (USVI). Given the high virulence and infection rates of WB and WPX, mitigation treatments should be explored. It is highly suspected both diseases have bacterial pathogens, even though Henle-Koch’s postulates have not been fulfilled to determine the causative agent for WB nor WPX observed in the USVI. A specialized antibiotic paste utilizing amoxicillin trihydrate has successfully been usedin situto mitigate another disease impacting stony corals, stony coral tissue loss disease (SCTLD). Considering the past success of this topical paste, this study aimed to determine if this treatment could be used onA. palmataandA. cervicornisto treat WPX and WB, respectively. The topical antibiotic paste did not significantly halt disease lesion expansion, nor stop new lesions from forming. Therefore, other mitigation treatments for WB and WPX should be considered. 

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4. Leveraging machine learning to classify and characterize gene expression patterns in two coral diseases

   https://doi.org/10.1007/s42452-025-07382-7  

   Van_Buren, Emily W; Beavers, Kelsey M; Cornelio, Mariah N; Stokes, Alexia; Emery, Madison; Brandt, Marilyn E; Demuth, Jeffery P; Wang, Li; Mydlarz, Laura D (September 2025, Discover Applied Sciences)

   Abstract Anthropogenic climate change has had devastating effects on the Florida and Caribbean reef systems, in part due to increased disease outbreaks. Climate change exacerbates marine diseases by expanding pathogen ranges and heightening host susceptibility through environmental stress. Specifically, there has been a stark rise in marine disease events outbreaks targeting multiple coral species, resulting in high mortality rates and declining reef biodiversity. Although many of these diseases present similar visual symptoms, they exhibit varying mortality rates and require distinct treatment protocols. Advances in coral transcriptomics research have enhanced our understanding of coral responses to various diseases, but more sophisticated methods are required to classify diseases that appear visually similar. This study provides the first machine learning (ML) model that can classify two common coral diseases: stony coral tissue loss disease (SCTLD) and white plague (WP). Using various algorithms, 463 gene expression biomarkers were identified, with 275 unique to SCTLD and 167 unique to WP, revealing distinct immune responses between the two diseases. The final ML model was built with partial least squares discriminant analysis (PLS-DA) and the identified biomarkers were tested and validated with samples collected in situ. It achieved high predictive performance, with an Area Under the Receiver Operating Characteristic (ROC) Curve (AUC) of 0.9895, an average overall error rate of 0.0754, and an average balanced error rate (BER) of 0.0799. This study provides a preliminary disease classification model that reliably distinguishes between SCTLD and WP and offers valuable insights into their underlying cellular responses. Additionally, the identified biomarkers provide a foundation for the development of rapid diagnostic tools to identify and mitigate future coral disease outbreaks. 

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5. Variable Species Responses to Experimental Stony Coral Tissue Loss Disease (SCTLD) Exposure

   https://doi.org/10.3389/fmars.2021.670829  

   Meiling, Sonora S.; Muller, Erinn M.; Lasseigne, Danielle; Rossin, Ashley; Veglia, Alex J.; MacKnight, Nicholas; Dimos, Bradford; Huntley, Naomi; Correa, Adrienne M.; Smith, Tyler Burton; et al (April 2021, Frontiers in Marine Science)

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   Stony coral tissue loss disease (SCTLD) was initially documented in Florida in 2014 and outbreaks with similar characteristics have since appeared in disparate areas throughout the northern Caribbean, causing significant declines in coral communities. SCTLD is characterized by focal or multifocal lesions of denuded skeleton caused by rapid tissue loss and affects at least 22 reef-building species of Caribbean corals. A tissue-loss disease consistent with the case definition of SCTLD was first observed in the U.S. Virgin Islands (USVI) in January of 2019 off the south shore of St. Thomas at Flat Cay. The objective of the present study was to characterize species susceptibility to the disease present in St. Thomas in a controlled laboratory transmission experiment. Fragments of six species of corals ( Colpophyllia natans , Montastraea cavernosa , Orbicella annularis , Porites astreoides , Pseudodiploria strigosa , and Siderastrea siderea ) were simultaneously incubated with (but did not physically contact) SCTLD-affected colonies of Diploria labyrinthiformis and monitored for lesion appearance over an 8 day experimental period. Paired fragments from each corresponding coral genotype were equivalently exposed to apparently healthy colonies of D. labyrinthiformis to serve as controls; none of these fragments developed lesions throughout the experiment. When tissue-loss lesions appeared and progressed in a disease treatment, the affected coral fragment, and its corresponding control genet, were removed and preserved for future analysis. Based on measures including disease prevalence and incidence, relative risk of lesion development, and lesion progression rates, O. annularis, C. natans , and S. siderea showed the greatest susceptibility to SCTLD in the USVI. These species exhibited earlier average development of lesions, higher relative risk of lesion development, greater lesion prevalence, and faster lesion progression rates compared with the other species, some of which are considered to be more susceptible based on field observations (e.g., P. strigosa ). The average transmission rate in the present study was comparable to tank studies in Florida, even though disease donor species differed. Our findings suggest that the tissue loss disease affecting reefs of the USVI has a similar epizootiology to that observed in other regions, particularly Florida. 

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