Effects of the Stony Coral Tissue Loss Disease Outbreak on Coral Communities and the Benthic Composition of Cozumel Reefs

In the Caribbean, disease outbreaks have emerged as significant drivers of coral mortality. Stony Coral Tissue Loss Disease (SCTLD) is a novel white plague-type disease that was first reported off the Florida coast in 2014. This disease affects >20 coral species and is spreading rapidly throughout the Caribbean. In December 2018, SCTLD reached southwestern (SW) Cozumel, one of the healthiest reef systems in the Caribbean. In this study, we integrate data from multiple survey protocols conducted between July 2018 and April 2020 to track the progression of the outbreak in SW Cozumel and to quantify the impacts of SCTLD on coral communities and the benthic composition of reefs. Given that the SCTLD outbreak coincided with a period of prolonged thermal stress that concluded in widespread coral bleaching in autumn 2019, we also investigated whether this event further exacerbated coral mortality. Our findings show that SCTLD spread throughout SW Cozumel in only 2 months and reached a peak after only 5 months. By the summer of 2019, most of the afflicted corals were already dead. Species of the families Meandrinidae, Faviinae, and Montastraeidae showed 33–95% mortality. The widespread coral die-off caused an overall loss of 46% in coral cover followed by a rapid increase of algae cover across all surveyed reefs that persisted until at least April 2020. In November 2019, more than 15% of surveyed coral colonies were bleached. However, we did not find that bleaching further increased coral mortality at either the colony or the community level, which suggests that the coral communities were able to recover from this event despite still being affected by the disease. In conclusion, SCTLD is radically changing the ecology of coral reefs by decimating the populations of several key reef-builders and reconfiguring the benthic assemblages. The actions needed to restore coral populations have to be accompanied by stringent controls related to the effects of climate change, coastal development, and wastewater treatment to improve coral conditions and ecosystem resilience.

Download Full-text

Impacts of Stony Coral Tissue Loss Disease (SCTLD) on Coral Community Structure at an Inshore Patch Reef of the Upper Florida Keys Using Photomosaics

Frontiers in Marine Science ◽

10.3389/fmars.2021.682163 ◽

2021 ◽

Vol 8 ◽

Author(s):

Graham Kolodziej ◽

Michael S. Studivan ◽

Arthur C. R. Gleason ◽

Chris Langdon ◽

Ian C. Enochs ◽

...

Keyword(s):

Community Structure ◽

Coral Reef ◽

Coral Cover ◽

Florida Keys ◽

Coral Community ◽

Tissue Loss ◽

Coral Tissue ◽

Coral Mortality ◽

Stony Coral ◽

Reef Tract

Since the appearance of stony coral tissue loss disease (SCTLD) on reefs off Miami in 2014, this unprecedented outbreak has spread across the entirety of Florida’s coral reef tract, as well as to many territories throughout the Caribbean. The endemic zone reached the upper Florida Keys by 2016, resulting in partial or complete mortality of coral colonies across numerous species. Disease was first observed at Cheeca Rocks (Islamorada, Florida) in the beginning of 2018, with reports of coral mortality peaking mid-year. The disease was still present at Cheeca Rocks as of March 2020, however, to a lesser degree compared to the initial outbreak. Annual monitoring efforts have been ongoing at Cheeca Rocks since 2012, including repeated benthic photomosaics of a 330 m2 survey zone, spanning six replicate sites. As such, a repository of coral community composition data exists for before and after the disease outbreak that was analyzed to assess the impacts of SCTLD on reef communities at an upper Florida Keys inshore reef. Cheeca Rocks is hypothesized to be a resilient reef due to its persistent high coral cover despite its inshore location, which subjects corals to fluctuating water quality and marginal environmental conditions. Coral populations here have been shown to recover from bleaching events and heat stress with minimal coral mortality. Though colonies of coral species characterized as highly and moderately susceptible to SCTLD (e.g., Colpophyllia natans, Diploria labyrinthiformis, Pseudodiploria strigosa, Orbicella annularis, and O. faveolata) suffered mortality as a result of the outbreak with an average loss of 16.42% relative cover by species, the overall impacts on coral cover and community structure were relatively low, contributing to a loss of total coral cover of only 1.65%. Comparison of photomosaic data to other studies indicate Cheeca Rocks may not have been affected as severely as other sites on Florida’s coral reef tract, underlying this site’s potential role in coral resilience to stressors including bleaching events, land-based pollution, and disease epizootics.

Download Full-text

Prevalence of Stony Coral Tissue Loss Disease at El Seco, a Mesophotic Reef System off Vieques Island, Puerto Rico

Frontiers in Marine Science ◽

10.3389/fmars.2021.668669 ◽

2021 ◽

Vol 8 ◽

Author(s):

Stacey M. Williams ◽

Jorge García-Sais ◽

Jorge Sabater-Clavell

Keyword(s):

Puerto Rico ◽

Coral Reef ◽

Coral Cover ◽

Coral Disease ◽

Tissue Loss ◽

Coral Tissue ◽

Stony Coral ◽

Reef System ◽

Coral Communities ◽

Mesophotic Reef

Mesophotic coral ecosystems (MCEs) are ecologically and functionally vital, as they are Essential Fish Habitats that function as refugia for corals and sponges of shallow-water reefs. Stony Coral Tissue Loss Disease (SCTLD) is a relatively new lethal coral disease, first affecting coral reefs in Florida and has now spread through most of the Caribbean. SCTLD was observed in Puerto Rico in December 2019 in Culebra Island. Since then, SCTLD has appeared along the east coast of Puerto Rico, affecting primarily shallow reefs in San Juan, Culebra and Vieques Island, and Fajardo. During late June and July 2020, four mesophotic reef habitats were surveyed at El Seco (off Vieques Island), on the southeast coast of Puerto Rico. SCTLD was observed at colonized pavement (CPRT – 23–30 m), bank coral reef (BCR – 35–40 m), patch coral reef (PCR – 36–42 m), and rhodolith (Rhodo – 40–50 m) habitats. The mean percent substrate cover by sessile-benthic categories varied significantly between habitats (PERMANOVA, p < 0.001), with a higher mean (± SE) coral cover at BCR (26.95 ± 5.60%), followed by PCR (12.88 ± 3.88%). SCTLD was detected in all habitats, but the disease prevalence was significantly higher at BCR, ranging from 9.70 to 21.13% of colonies infected (Kruskal-Wallis ANOVA, p < 0.007). Even though PCR habitats exhibited less coral cover, SCTLD prevalence was still elevated ranging from 6.66 to 15.07%. The deepest record of SCTLD at El Seco was 40.9 m. The majority (∼98%) of the corals infected with the disease were from the Orbicella complex spp. (faveolata/franksi). However, there were other infected species, such as Agaricia grahamae, A. lamarcki, Montastraea cavernosa, and Porites astreoides. As seen in the surveys conducted in 2011 and 2020, the loss of coral cover allows for the emergence of other benthic “detractors,” such as peyssonnelids, specifically Ramicrusta spp. Ramicrusta spp., an aggressive encrusting red alga known to take over available space and overgrow corals, significantly increased its substrate cover at the impacted reefs. Therefore, the severity and virulence of SCTLD will most likely have severe and long-lasting negative impacts on the coral communities at El Seco mesophotic reef system.

Download Full-text

The Emergence and Initial Impact of Stony Coral Tissue Loss Disease (SCTLD) in the United States Virgin Islands

Frontiers in Marine Science ◽

10.3389/fmars.2021.715329 ◽

2021 ◽

Vol 8 ◽

Author(s):

Marilyn E. Brandt ◽

Rosmin S. Ennis ◽

Sonora S. Meiling ◽

Joseph Townsend ◽

Kathryn Cobleigh ◽

...

Keyword(s):

Coral Cover ◽

The United States ◽

Virgin Islands ◽

Disease Prevalence ◽

Tissue Loss ◽

Coral Tissue ◽

Focal Lesions ◽

Stony Coral ◽

Coral Communities ◽

The U.S

Coral communities in the Caribbean face a new and deadly threat in the form of the highly virulent multi-host stony coral tissue loss disease (SCTLD). In late January of 2019, a disease with signs and characteristics matching that of SCTLD was found affecting a reef off the coast of St. Thomas in the U.S. Virgin Islands (USVI). Identification of its emergence in the USVI provided the opportunity to document the initial evolution of its spatial distribution, coral species susceptibility characteristics, and its comparative impact on coral cover at affected and unaffected coral reef locations. Re-assessments at sentinel sites and long-term monitoring locations were used to track the spread of the disease, assess species affected, and quantify its impact. The disease was initially limited to the southwest of St. Thomas for several months, then spread around the island and to the neighboring island of St. John to the east. Differences in disease prevalence among species were similar to reports of SCTLD from other regions. Highly affected species included Colpophyllia natans, Eusmilia fastigiata, Montastraea cavernosa, Orbicella spp., and Pseudodiploria strigosa. Dendrogyra cylindrus and Meandrina meandrites were also highly affected but showed more variability in disease prevalence, likely due to initial low abundances and the rapid loss of colonies due to disease. Siderastrea spp. were less affected and showed lower prevalence. Species previously reported as unaffected or data deficient that were found to be affected by SCTLD included Agaricia spp., Madracis spp., and Mycetophyllia spp. We also observed multi-focal lesions at SCTLD-affected sites on colonies of Porites astreoides, despite that poritids have previously been considered low or not susceptible to SCTLD. Loss of coral cover due to acute tissue loss diseases, which were predominantly SCTLD, was significant at several monitoring locations and was more impactful than previous mass bleaching events at some sites. There are no signs that the USVI SCTLD outbreak is abating, therefore it is likely that this disease will become widespread across the U.S. Caribbean and British Virgin Islands in the near future.

Download Full-text

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

Frontiers in Marine Science ◽

10.3389/fmars.2021.815698 ◽

2022 ◽

Vol 8 ◽

Author(s):

Michael S. Studivan ◽

Ashley M. Rossin ◽

Ewelina Rubin ◽

Nash Soderberg ◽

Daniel M. Holstein ◽

...

Keyword(s):

Infectious Agent ◽

Coastal Development ◽

Ex Situ ◽

Tissue Loss ◽

Coral Tissue ◽

Conservation Strategies ◽

Dade County ◽

Tissue Samples ◽

Stony Coral ◽

The Individual

Stony coral tissue loss disease (SCTLD) was first observed in 2014 near Virginia Key in Miami-Dade County, Florida. Field sampling, lab experiments, and modeling approaches have suggested that reef sediments may play a role in SCTLD transmission, though a positive link has not been tested experimentally. We conducted an ex situ transmission assay using a statistically-independent disease apparatus to test whether reef sediments can transmit SCTLD in the absence of direct contact between diseased and healthy coral tissue. We evaluated two methods of sediment inoculation: batch inoculation of sediments collected from southeast Florida using whole colonies of diseased Montastraea cavernosa, and individual inoculations of sediments following independent, secondary infections of ∼5 cm2 coral fragments. Healthy fragments of the coral species Orbicella faveolata and M. cavernosa were exposed to these diseased sediment treatments, as well as direct disease contact and healthy sediment controls. SCTLD transmission was observed for both batch and individual diseased sediment inoculation treatments, albeit with lower proportions of infected individuals as compared to disease contact controls. The time to onset of lesions was significantly different between species and among disease treatments, with the most striking infections occurring in the individual diseased sediment treatment in under 24 h. Following infection, tissue samples were confirmed for the presence of SCTLD signs via histological examination, and sediment subsamples were analyzed for microbial community variation between treatments, identifying 16 SCTLD indicator taxa in sediments associated with corals experiencing tissue loss. This study demonstrated that reef sediments can indeed transmit SCTLD through indirect exposure between diseased and healthy corals, and adds credence to the assertion that SCTLD transmission occurs via an infectious agent or agents. This study emphasizes the critical need to understand the roles that sediment microbial communities and coastal development activities may have on the persistence of SCTLD throughout the endemic zone, especially in the context of management and conservation strategies in Florida and the wider Caribbean.

Download Full-text

Similarities and Differences Between Two Deadly Caribbean Coral Diseases: White Plague and Stony Coral Tissue Loss Disease

Frontiers in Marine Science ◽

10.3389/fmars.2021.709544 ◽

2021 ◽

Vol 8 ◽

Author(s):

Aldo Cróquer ◽

Ernesto Weil ◽

Caroline S. Rogers

Keyword(s):

Mortality Rates ◽

Case Definition ◽

Tissue Loss ◽

Coral Tissue ◽

Coral Diseases ◽

Stony Coral ◽

Coral Microbiome ◽

White Plague ◽

The Caribbean ◽

Multiple Species

For several decades, white plagues (WPDs: WPD-I, II and III) and more recently, stony coral tissue loss disease (SCTLD) have significantly impacted Caribbean corals. These diseases are often difficult to separate in the field as they produce similar gross signs. Here we aimed to compare what we know about WPD and SCTLD in terms of: (1) pathology, (2) etiology, and (3) epizootiology. We reviewed over 114 peer-reviewed publications from 1973 to 2021. Overall, WPD and SCTLD resemble each other macroscopically, mainly due to the rapid tissue loss they produce in their hosts, however, SCTLD has a more concise case definition. Multiple-coalescent lesions are often observed in colonies with SCTLD and rarely in WPD. A unique diagnostic sign of SCTLD is the presence of bleached circular areas when SCTLD lesions are first appearing in the colony. The paucity of histopathologic archives for WPDs for multiple species across geographies makes it impossible to tell if WPD is the same as SCTLD. Both diseases alter the coral microbiome. WPD is controversially regarded as a bacterial infection and more recently a viral infection, whereas for SCTLD the etiology has not been identified, but the putative pathogen, likely to be a virus, has not been confirmed yet. Most striking differences between WPD and SCTLD have been related to duration and phases of epizootic events and mortality rates. While both diseases may become highly prevalent on reefs, SCTLD seems to be more persistent even throughout years. Both transmit directly (contact) and horizontally (waterborne), but organism-mediated transmission is only proven for WPD-II. Given the differences and similarities between these diseases, more detailed information is needed for a better comparison. Specifically, it is important to focus on: (1) tagging colonies to look at disease progression and tissue mortality rates, (2) tracking the fate of the epizootic event by looking at initial coral species affected, the features of lesions and how they spread over colonies and to a wider range of hosts, (3) persistence across years, and (4) repetitive sampling to look at changes in the microbiome as the disease progresses. Our review shows that WPDs and SCTLD are the major causes of coral tissue loss recorded in the Caribbean.

Download Full-text

A rapid spread of the Stony Coral Tissue Loss Disease outbreak in the Mexican Caribbean

10.7287/peerj.preprints.27893v1 ◽

2019 ◽

Cited By ~ 1

Author(s):

Lorenzo Alvarez-Filip ◽

Nuria Estrada-Saldívar ◽

Esmeralda Pérez-Cervantes ◽

Ana Molina-Hernández ◽

Francisco J. Gonzalez-Barrios

Keyword(s):

Coral Disease ◽

Disease Outbreak ◽

Disease Prevalence ◽

Tissue Loss ◽

Coral Tissue ◽

Similar Species ◽

Western Atlantic ◽

Stony Coral ◽

Mexican Caribbean ◽

Coral Communities

Caribbean reef corals have experienced unprecedented declines from climate change, anthropogenic stressors and infectious diseases in recent decades. Since 2014 a highly lethal, new disease, called stony coral tissue loss disease (SCTLD), has impacted many species in Florida. During the summer of 2018 we noticed an anomalously high disease prevalence affecting different coral species in the northern portion of the Mexican Caribbean. We assessed the severity of this outbreak in 2018/2019 using the AGRRA coral protocol to survey 82 reef sites across the Mexican Caribbean. Then, using a subset of 14 sites we detailed information from before the outbreak (2016/2017) to explore the consequences of the disease on the condition and composition of coral communities. Our findings show that the disease outbreak has already spread across the entire region, affecting similar species (with similar disease patterns) to those previously described for Florida. However, we observed a great variability in prevalence and tissue mortality that was not attributable to any geographical gradient. Using long-term data, we determined that there is no evidence of such high coral disease prevalence anywhere in the region before 2018, which suggests that the entire Mexican Caribbean (~450 km) was afflicted by the disease within a few months. The analysis of sites that contained pre-outbreak information showed that this event considerably increased coral mortality and severely changed the structure of coral communities in the region. Given the high prevalence and lethality of this disease, and the high number of susceptible species, we encourage reef researchers, managers and stakeholders across the Western Atlantic to accord it the highest priority for the near future.

Download Full-text

Fine Scale Temporal and Spatial Dynamics of the Stony Coral Tissue Loss Disease Outbreak Within the Lower Florida Keys

Frontiers in Marine Science ◽

10.3389/fmars.2021.631776 ◽

2021 ◽

Vol 8 ◽

Author(s):

Sara D. Williams ◽

Cory S. Walter ◽

Erinn M. Muller

Keyword(s):

Spatial Clustering ◽

Coral Cover ◽

Spatial Scales ◽

Florida Keys ◽

Incidence Rates ◽

Tissue Loss ◽

Coral Tissue ◽

Maximum Temperature ◽

Small Scale ◽

Stony Coral

One of the latest threats to Florida’s Coral Reef is the stony coral tissue loss disease (SCTLD) outbreak which affects all but a few Caribbean scleractinian species and has spread throughout the Caribbean since 2014. Without a known pathogen, ecological studies of disease dynamics are essential for understanding SCTLD susceptibility at the individual colony and reef level. We investigated the epizootiology of the SCTLD outbreak in the lower Florida Keys at two spatial scales (among reefs ∼1 km and within reefs <10 m) over a 19 month period. In May 2018, three sites absent of SCTLD were established to characterize coral demographics (i.e., live tissue cover and colony diameter) along an offshore to nearshore gradient, and were subsequently surveyed for disease every 2–3 weeks until December 2019. SCTLD was first noted within the offshore and mid-channel reef sites in early October 2018 and later appeared at the nearshore site in early February 2019. SCTLD was negatively correlated with thermal stress, showing reduced progression and incidence rates after 2–3 weeks of water temperatures above the mean monthly maximum temperature for the region (i.e., 2–3 degree heating weeks). Although Pseudodiploria strigosa, Dichocoenia stokesii, Colpophyllia natans, and Diploria labyrinthiformis were the most susceptible species at our sites, areas with more Montastraea cavernosa and Orbicella faveolata colonies had higher prevalence and greater tissue loss associated with disease. The disease was more severe within quadrats with high species diversity, high coral cover, and disproportionately affected larger colonies. Our spatial analyses suggest that (1) SCTLD followed a contagious disease model within small (<10 m) spatial scales, (2) colonies within 1.5–3 m of a diseased coral were at higher risk for subsequently showing disease signs compared with those farther away, and (3) high incidence rates coincided with the loss of small scale (<10 m radius) spatial clustering, suggesting pulses of contagious spread on large spatial scales.

Download Full-text

A rapid spread of the stony coral tissue loss disease outbreak in the Mexican Caribbean

PeerJ ◽

10.7717/peerj.8069 ◽

2019 ◽

Vol 7 ◽

pp. e8069 ◽

Cited By ~ 12

Author(s):

Lorenzo Alvarez-Filip ◽

Nuria Estrada-Saldívar ◽

Esmeralda Pérez-Cervantes ◽

Ana Molina-Hernández ◽

Francisco J. González-Barrios

Keyword(s):

Coral Species ◽

Disease Outbreak ◽

Disease Prevalence ◽

Tissue Loss ◽

Coral Tissue ◽

Similar Species ◽

Western Atlantic ◽

Stony Coral ◽

Mexican Caribbean ◽

Coral Communities

Caribbean reef corals have experienced unprecedented declines from climate change, anthropogenic stressors and infectious diseases in recent decades. Since 2014, a highly lethal, new disease, called stony coral tissue loss disease, has impacted many reef-coral species in Florida. During the summer of 2018, we noticed an anomalously high disease prevalence affecting different coral species in the northern portion of the Mexican Caribbean. We assessed the severity of this outbreak in 2018/2019 using the AGRRA coral protocol to survey 82 reef sites across the Mexican Caribbean. Then, using a subset of 14 sites, we detailed information from before the outbreak (2016/2017) to explore the consequences of the disease on the condition and composition of coral communities. Our findings show that the disease outbreak has already spread across the entire region by affecting similar species (with similar disease patterns) to those previously described for Florida. However, we observed a great variability in prevalence and tissue mortality that was not attributable to any geographical gradient. Using long-term data, we determined that there is no evidence of such high coral disease prevalence anywhere in the region before 2018, which suggests that the entire Mexican Caribbean was afflicted by the disease within a few months. The analysis of sites that contained pre-outbreak information showed that this event considerably increased coral mortality and severely changed the structure of coral communities in the region. Given the high prevalence and lethality of this disease, and the high number of susceptible species, we encourage reef researchers, managers and stakeholders across the Western Atlantic to accord it the highest priority for the near future.

Download Full-text

Measuring Stony Coral Tissue Loss Disease Induction and Lesion Progression Within Two Intermediately Susceptible Species, Montastraea cavernosa and Orbicella faveolata

Frontiers in Marine Science ◽

10.3389/fmars.2021.717265 ◽

2021 ◽

Vol 8 ◽

Author(s):

Katherine R. Eaton ◽

Jan H. Landsberg ◽

Yasunari Kiryu ◽

Esther C. Peters ◽

Erinn M. Muller

Keyword(s):

Basal Body ◽

Direct Contact ◽

Coral Cover ◽

Physical Contact ◽

Tissue Loss ◽

Coral Tissue ◽

Progression Rate ◽

Stony Coral ◽

Orbicella Faveolata ◽

Montastraea Cavernosa

During the last several decades, Florida’s Coral Reef (FCR) has been impacted by both global and local stressors that have devastated much of its living coral cover. Additionally, since 2014 FCR has experienced a lethal disease outbreak termed stony coral tissue loss disease (SCTLD). Here, we examined SCTLD spreading dynamics within and among fragmented coral colonies and quantified lesion progression rate of two intermediately susceptible species—Montastraea cavernosa and Orbicella faveolata—through induction experiments conducted in laboratory aquaria. M. cavernosa colonies showing subacute tissue loss were sequentially fragmented parallel to the lesion edge to determine whether isolated tissue that showed no tissue-loss signs, referred to as isolated apparently healthy (AH) donor fragments, would subsequently exhibit tissue loss. Additionally, AH M. cavernosa and O. faveolata fragments, referred to as recipient fragments, were placed in direct contact with the M. cavernosa donor fragments to assess incidence of new tissue-loss lesions. Finally, AH M. cavernosa donor fragments were placed in direct contact with recipient M. cavernosa and O. faveolata fragments to account for aggression from direct contact. Samples were collected for histopathology of the corals through time. Many isolated AH donor fragments developed tissue-loss lesions during the 60-day study, suggesting SCTLD may be systemic within small-sized colonies. Our results confirmed that physical contact between recipient fragments and subacute SCTLD-lesioned tissue often led to tissue loss in recipient fragments. None of the control recipient or donor fragments experienced tissue loss. Grossly, multifocal lesions started on or adjacent to the septal and costal basal body walls with tissue loss progressing across the polyp septa and coenenchyme, respectively, in both species. Histologically, initial tissue-loss lesions in both species exhibited characteristic lytic necrosis (LN) at the basal body wall of the gastrodermis. O. faveolata exhibited higher rates of lesion appearance and subsequent mortality compared to M. cavernosa, but once a lesion appeared, M. cavernosa lost tissue faster than O. faveolata. This work contributes to the growing knowledge of SCTLD dynamics and highlights the differences in lesion progression within susceptible species.

Download Full-text

Evaluating the small-scale epidemiology of the stony-coral -tissue-loss-disease in the middle Florida Keys

PLoS ONE ◽

10.1371/journal.pone.0241871 ◽

2020 ◽

Vol 15 (11) ◽

pp. e0241871

Author(s):

William C. Sharp ◽

Colin P. Shea ◽

Kerry E. Maxwell ◽

Erinn M. Muller ◽

John H. Hunt

Keyword(s):

Disease Transmission ◽

Positive Association ◽

Florida Keys ◽

Mitigation Strategies ◽

Tissue Loss ◽

Coral Tissue ◽

Small Scale ◽

Stony Coral ◽

Frequency Monitoring ◽

Coral Communities

Along the Florida reef tract, stony-coral-tissue-loss disease (SCTLD) has caused extensive mortality of more than 20 scleractinian coral species. The pathogen is unknown, but its epizoology indicates that the disease, facilitated by water currents, has progressed linearly along the tract, affecting reefs at the scale of hundreds of kilometers. To inform ongoing disease mitigation efforts, we examined the small-scale spatial and temporal epidemiology of SCTLD. We established a series of sites in the middle Florida Keys at offshore and inshore locations that had not yet shown signs of SCTLD. We then conducted high-frequency monitoring from February 2018 through September 2019 and documented the onset of SCTLD and its progression through the sites. SCTLD was first observed at one site during early February 2018 and by early March 2018 all sites showed signs of the disease. A dynamic multistate model suggested that disease transmission was independent of coral density and found little evidence of a positive association between a colony showing signs of SCTLD and the condition or distance to its neighboring colonies. The model did, however, indicate that the probability of a colony showing signs of SCTLD increased with increasing colony surface area. These results are consistent with the water-borne transmission of a pathogen that progressed rapidly through the survey area. However, by the end of our survey the progression of SCTLD had slowed, particularly at inshore sites. Many affected colonies no longer exhibited progressive tissue mortality typical of the disease, suggesting the existence of differentially resilient colonies or coral communities, meriting their use for future coral rescue and propagation and disease research. These results are useful for refining ongoing SCTLD mitigation strategies, particularly by determining when disease rates are sufficiently low for direct intervention efforts designed to arrest disease progression on individual coral colonies will be most effective.

Download Full-text