Multi-Factor Coral Disease Risk: A new product for early warning and management.

Ecological forecasts are becoming increasingly valuable tools for conservation and management. However, there are few examples of near-real-time forecasting systems that account for the wide range of ecological complexities. We developed a new coral disease ecological forecasting system that explores a suite of ecological relationships and their uncertainty and investigates how forecast skill changes with shorter lead times. The Multi-Factor Coral Disease Risk product introduced here uses a combination of ecological and marine environmental conditions to predict the risk of white syndromes and growth anomalies across reefs in the central and western Pacific and along the east coast of Australia and is available through the US National Oceanic and Atmospheric Administration Coral Reef Watch program. This product produces weekly forecasts for a moving window of 6 months at a resolution of ~5 km based on quantile regression forests. The forecasts show superior skill at predicting disease risk on withheld survey data from 2012 to 2020 compared with predecessor forecast systems, with the biggest improvements shown for predicting disease risk at mid- to high-disease levels. Most of the prediction uncertainty arises from model uncertainty, so prediction accuracy and precision do not improve substantially with shorter lead times. This result arises because many predictor variables cannot be accurately forecasted, which is a common challenge across ecosystems. Weekly forecasts and scenarios can be explored through an online decision support tool and data explorer, co-developed with end-user groups to improve use and understanding of ecological forecasts. The models provide near-real-time disease risk assessments and allow users to refine predictions and assess intervention scenarios. This work advances the field of ecological forecasting with real-world complexities and, in doing so, better supports near-term decision making for coral reef ecosystem managers and stakeholders. Secondarily, we identify clear needs and provide recommendations to further enhance our ability to forecast coral disease risk.

Spatial extent of dysbiosis in the branching coral Pocillopora damicornis during an acute disease outbreak.

Globally, coral reefs face increasing disease prevalence and large-scale outbreak events. These outbreaks offer insights into microbial and functional patterns of coral disease, including early indicators of disease that may be present in visually-healthy tissues. Outbreak events also allow investigation of how reef-building corals, typically colonial organisms, respond to disease. We studied Pocillopora damicornis during an acute tissue loss disease outbreak on Guam to determine whether dysbiosis was present in visually-healthy tissues ahead of advancing disease lesions. These data reveal that coral fragments with visual evidence of disease are expectedly dysbiotic with high microbial and metabolomic variability. However, visually-healthy tissues from the same colonies lacked dysbiosis, suggesting disease containment near the affected area. These results challenge the idea of using broad dysbiosis as a pre-visual disease indicator and prompt reevaluation of disease assessment in colonial organisms such as reef-building corals.

Calcium homeostasis disruption initiates rapid growth after micro-fragmentation in the scleractinian coral Porites lobata.

Coral reefs are ecosystems under increasing threat from global climate change. Coral restoration is a tool for preserving the biological and ecological function of coral reefs by mitigating coral loss and maintaining the structural integrity and complexity of reefs. To generate the necessary stock for coral restoration, larger coral colonies are usually fragmented to generate smaller specimens for outplanting, taking advantage of the high regenerative ability of corals. In this study, we utilized RNA-seq technology to understand the physiological responses of Porites lobata colonies to physical fragmentation and outplanting, which have thus far not been characterized. Our results demonstrate that P. lobata fragments undergoing physical injury recover through two distinct phases: rapid wound regeneration of the cut margins, followed by a slower growth phase that cements the colony to the substrate. Our study found rapid physiological responses to acute physical injury and outplanting in the coral host that involved significantly increased energy production, calcium homeostasis disruption, and endoplasmic reticulum (ER) stress leading to increased antioxidant expression and rates of protein turnover. Our results suggest that phosphoinositide-mediated acute calcium homeostasis disruption stimulates wound recovery processes in response to physical injury. Symbiont gene expression revealed extremely low gene differences in response to fragmentation, growth, and outplanting. These results provide insight into the physiological mechanisms that allow for rapid wound healing and stabilization in response to physical injury in corals.

Going with the flow: How corals in high-flow environments can beat the heat.

Coral reefs are experiencing unprecedented declines in health on a global scale leading to severe reductions in coral cover. One major cause of this decline is increasing sea surface temperature. However, conspecific colonies separated by even small spatial distances appear to show varying responses to this global stressor. One factor contributing to differential responses to heat stress is variability in the coral's micro-environment, such as the amount of water flow a coral experiences. High flow provides corals with a variety of health benefits, including heat stress mitigation. Here, we investigate how water flow affects coral gene expression and provides resilience to increasing temperatures. We examined host and photosymbiont gene expression of Acropora cf. pulchra colonies in discrete in situ flow environments during a natural bleaching event. In addition, we conducted controlled ex situ tank experiments where we exposed A. cf. pulchra to different flow regimes and acute heat stress. Notably, we observed distinct flow-driven transcriptomic signatures related to energy expenditure, growth, heterotrophy and a healthy coral host-photosymbiont relationship. We also observed disparate transcriptomic responses during bleaching recovery between the high- and low-flow sites. Additionally, corals exposed to high flow showed "frontloading" of specific heat-stress-related genes such as heat shock proteins, antioxidant enzymes, genes involved in apoptosis regulation, innate immunity and cell adhesion. We posit that frontloading is a result of increased oxidative metabolism generated by the increased water movement. Gene frontloading may at least partially explain the observation that colonies in high-flow environments show higher survival and/or faster recovery in response to bleaching events.

Compositional homogeneity in the pathobiome of a new, slow-spreading coral disease.

BACKGROUND: Coral reefs face unprecedented declines in diversity and cover, a development largely attributed to climate change-induced bleaching and subsequent disease outbreaks. Coral-associated microbiomes may strongly influence the fitness of their hosts and alter heat tolerance and disease susceptibility of coral colonies. Here, we describe a new coral disease found in Micronesia and present a detailed assessment of infection-driven changes in the coral microbiome. RESULTS: Combining field monitoring and histological, microscopic and next-generation barcoding assessments, we demonstrate that the outbreak of the disease, named 'grey-patch disease', is associated with the establishment of cyanobacterial biofilm overgrowing coral tissue. The disease is characterised by slow progression rates, with coral tissue sometimes growing back over the GPD biofilm. Network analysis of the corals' microbiome highlighted the clustering of specific microbes which appeared to benefit from the onset of disease, resulting in the formation of 'infection clusters' in the microbiomes of apparently healthy corals. CONCLUSIONS: Our results appear to be in contrast to the recently proposed Anna-Karenina principle, which states that disturbances (such as disease) trigger chaotic dynamics in microbial communities and increase ß-diversity. Here, we show significantly higher community similarity (compositional homogeneity) in the pathobiome of diseased corals, compared to the microbiome associated with apparently healthy tissue. A possible explanation for this pattern is strong competition between the pathogenic community and those associated with the 'healthy' coral holobiont, homogenising the composition of the pathobiome. Further, one of our key findings is that multiple agents appear to be involved in degrading the corals' defences causing the onset of this disease. This supports recent findings indicating a need for a shift from the one-pathogen-one-disease paradigm to exploring the importance of multiple pathogenic players in any given disease.

Chemical and Metagenomic Studies of the Lethal Black Band Disease of Corals Reveal Two Broadly Distributed, Redox-Sensitive Mixed Polyketide/Peptide Macrocycles.

Black band disease (BBD), a lethal, polymicrobial disease consortium dominated by the cyanobacterium Roseofilum reptotaenium, kills many species of corals worldwide. To uncover chemical signals or cytotoxins that could be important in proliferation of Roseofilum and the BBD layer, we examined the secondary metabolites present in geographically diverse collections of BBD from Caribbean and Pacific coral reefs. Looekeyolide A (1), a 20-membered macrocyclic compound formed by a 16-carbon polyketide chain, 2-deamino-2-hydroxymethionine, and d-leucine, and its autoxidation product looekeyolide B (2) were extracted as major compounds (∼1 mg g-1 dry wt) from more than a dozen field-collected BBD samples. Looekeyolides A and B were also produced by a nonaxenic R. reptotaenium culture under laboratory conditions at similar concentrations. R. reptotaenium genomes that were constructed from four different metagenomic data sets contained a unique nonribosomal peptide/polyketide biosynthetic cluster that is likely responsible for the biosynthesis of the looekeyolides. Looekeyolide A, which readily oxidizes to looekeyolide B, may play a biological role in reducing H2O2 and other reactive oxygen species that could occur in the BBD layer as it overgrows and destroys coral tissue.

Whale Shark Tourism: Impacts on Coral Reefs in the Philippines.

Reef-based tourism has been developing rapidly in recent decades yet its impacts on reef ecosystems are often overlooked. In Tan-awan, Oslob, Philippines, whale sharks are attracted to the shallow reefs where they are provisioned up to 50 tons y-1 of feed and this phenomenon in turn attracts >300,000 y-1 visitors. Given the intensive provisioning and concentrating tourism activities, we hypothesized that the whale shark tourism-impacted site (IS) will have greater impacts on reef degradation and higher anthropogenic nitrogen pollution level compared to its reference site (RS). Ecological surveys revealed that relative to the RS, the IS had 36% higher relative abundance of Pocillopora and Porites coral over other genera, >2.5-fold lower coral density, and 20% higher macroalgal cover, which we concluded are signs of reef degradation. Also, we conducted stable nitrogen isotope analysis on gorgonian skeletons to trace nitrogen sources at both sites through time. Although an average 1‰ isotope enrichment found in the IS relative to the RS could indicate anthropogenic nitrogen inputs in the IS, this enrichment was consistent over time and existed before the tourism developed. Despite that, we cautioned against the imminent threat of local eutrophication caused by the continued inputs of nitrogen derived from provisioning and tourism activities. In summary, this study provided the first documentation of the impacts of provisioned whale shark tourism on the local reefs in Tan-awan and established an ecological baseline for future comparisons. Such assessments can offer important information on reef health, coastal development, and tourism management.

Life and death of a sewage treatment plant recorded in a coral skeleton δ15N record.

We investigated the potential of coral skeleton δ15N (CS-δ15N) records for tracking anthropogenic-N sources in coral reef ecosystems. We produced a 56yr-long CS-δ15N record (1958-2014) from a reef flat in Guam that has been exposed to varying 1) levels of sewage treatment 2) population density, and 3) land use. Increasing population density (from <30 to 300ind·km-2) and land use changes in the watershed resulted in a ~1‰ enrichment of the CS-δ15N record until a sewage treatment plant (STP) started operation in 1975. Then, CS-δ15N stabilized, despite continued population density and land use changes. Based on population and other considerations, a continued increase in the sewage footprint might have been expected over this time. The stability of CS-δ15N, either contradicts this expectation, or indicates that the impacts on the outer reef at the coring site were buffered by the mixing of reef water with the open ocean.

Comparative Metagenomics of the Polymicrobial Black Band Disease of Corals.

Black Band Disease (BBD), the destructive microbial consortium dominated by the cyanobacterium Roseofilum reptotaenium, affects corals worldwide. While the taxonomic composition of BBD consortia has been well-characterized, substantially less is known about its functional repertoire. We sequenced the metagenomes of Caribbean and Pacific black band mats and cultured Roseofilum and obtained five metagenome-assembled genomes (MAGs) of Roseofilum, nine of Proteobacteria, and 12 of Bacteroidetes. Genomic content analysis suggests that Roseofilum is a source of organic carbon and nitrogen, as well as natural products that may influence interactions between microbes. Proteobacteria and Bacteroidetes members of the disease consortium are suited to the degradation of amino acids, proteins, and carbohydrates. The accumulation of sulfide underneath the black band mat, in part due to a lack of sulfur oxidizers, contributes to the lethality of the disease. The presence of sulfide:quinone oxidoreductase genes in all five Roseofilum MAGs and in the MAGs of several heterotrophs demonstrates that resistance to sulfide is an important characteristic for members of the BBD consortium.

Local-scale projections of coral reef futures and implications of the Paris Agreement.

Increasingly frequent severe coral bleaching is among the greatest threats to coral reefs posed by climate change. Global climate models (GCMs) project great spatial variation in the timing of annual severe bleaching (ASB) conditions; a point at which reefs are certain to change and recovery will be limited. However, previous model-resolution projections (~1 × 1°) are too coarse to inform conservation planning. To meet the need for higher-resolution projections, we generated statistically downscaled projections (4-km resolution) for all coral reefs; these projections reveal high local-scale variation in ASB. Timing of ASB varies >10 years in 71 of the 87 countries and territories with >500 km2 of reef area. Emissions scenario RCP4.5 represents lower emissions mid-century than will eventuate if pledges made following the 2015 Paris Climate Change Conference (COP21) become reality. These pledges do little to provide reefs with more time to adapt and acclimate prior to severe bleaching conditions occurring annually. RCP4.5 adds 11 years to the global average ASB timing when compared to RCP8.5; however, >75% of reefs still experience ASB before 2070 under RCP4.5. Coral reef futures clearly vary greatly among and within countries, indicating the projections warrant consideration in most reef areas during conservation and management planning.

Contrasting Lesion Dynamics of White Syndrome among the scleractinian corals Porites spp.

White syndrome (WS) is currently the most prevalent disease of scleractinian corals in the Indo-Pacific region, with an ability to exist in both epizootic and enzootic states. Here, we present results of an examination of WS lesion dynamics and show that potentially associated traits of host morphology (i.e., branching vs. massive), lesion size, and tissue deposition rate influence disease severity and recovery. Lesion healing rate was positively correlated with initial lesion size in both morphologies, but the rate at which lesions healed differed between morphologies. New lesions in branching Porites cylindrica appeared less frequently, were smaller and healed more quickly, but were more abundant than in closely-related massive Porites sp(p). The positive association between lesion size and healing rate was partly explained by geometry; branching limited lesion maximum size, and larger lesion margins contained more polyps producing new tissue, resulting in faster healing. However, massive colonies deposited tissue more slowly than branching colonies, resulting in slower recovery and more persistent lesions. Corallite size and density did not differ between species and did not, therefore, influence healing rate. We demonstrated multiple modes of pathogen transmission, which may be influenced by the greater potential for pathogen entrainment in branching vs. massive morphologies. We suggest that attributes such as colony morphology and species-specific growth rates require consideration as we expand our understanding of disease dynamics in colonial organisms such as coral.

Link between sewage-derived nitrogen pollution and coral disease severity in Guam.

The goals of this study were to evaluate the contribution of sewage-derived N to reef flat communities in Guam and to assess the impact of N inputs on coral disease. We used stable isotope analysis of macroalgae and a soft coral, sampled bimonthly, as a proxy for N dynamics, and surveyed Porites spp., a dominant coral taxon on Guam's reefs, for white syndrome disease severity. Results showed a strong influence of sewage-derived N in nearshore waters, with δ(15)N values varying as a function of species sampled, site, and sampling date. Increases in sewage-derived N correlated significantly with increases in the severity of disease among Porites spp., with δ(15)N values accounting for more than 48% of the variation in changes in disease severity. The anticipated military realignment and related population increase in Guam are expected to lead to increased white syndrome infections and other coral diseases.

Global coral disease prevalence associated with sea temperature anomalies and local factors.

Coral diseases are taking an increasing toll on coral reef structure and biodiversity and are important indicators of declining health in the oceans. We implemented standardized coral disease surveys to pinpoint hotspots of coral disease, reveal vulnerable coral families and test hypotheses about climate drivers from 39 locations worldwide. We analyzed a 3 yr study of coral disease prevalence to identify links between disease and a range of covariates, including thermal anomalies (from satellite data), location and coral cover, using a Generalized Linear Mixed Model. Prevalence of unhealthy corals, i.e. those with signs of known diseases or with other signs of compromised health, exceeded 10% on many reefs and ranged to over 50% on some. Disease prevalence exceeded 10% on 20% of Caribbean reefs and 2.7% of Pacific reefs surveyed. Within the same coral families across oceans, prevalence of unhealthy colonies was higher and some diseases were more common at sites in the Caribbean than those in the Pacific. The effects of high disease prevalence are potentially extensive given that the most affected coral families, the acroporids, faviids and siderastreids, are among the major reef-builders at these sites. The poritids and agaricids stood out in the Caribbean as being the most resistant to disease, even though these families were abundant in our surveys. Regional warm temperature anomalies were strongly correlated with high disease prevalence. The levels of disease reported here will provide a much-needed local reference point against which to compare future change.

Growth anomalies on the coral genera Acropora and Porites are strongly associated with host density and human population size across the Indo-Pacific.

Growth anomalies (GAs) are common, tumor-like diseases that can cause significant morbidity and decreased fecundity in the major Indo-Pacific reef-building coral genera, Acropora and Porites. GAs are unusually tractable for testing hypotheses about drivers of coral disease because of their pan-Pacific distributions, relatively high occurrence, and unambiguous ease of identification. We modeled multiple disease-environment associations that may underlie the prevalence of Acropora growth anomalies (AGA) (n = 304 surveys) and Porites growth anomalies (PGA) (n = 602 surveys) from across the Indo-Pacific. Nine predictor variables were modeled, including coral host abundance, human population size, and sea surface temperature and ultra-violet radiation anomalies. Prevalence of both AGAs and PGAs were strongly host density-dependent. PGAs additionally showed strong positive associations with human population size. Although this association has been widely posited, this is one of the first broad-scale studies unambiguously linking a coral disease with human population size. These results emphasize that individual coral diseases can show relatively distinct patterns of association with environmental predictors, even in similar diseases (growth anomalies) found on different host genera (Acropora vs. Porites). As human densities and environmental degradation increase globally, the prevalence of coral diseases like PGAs could increase accordingly, halted only perhaps by declines in host density below thresholds required for disease establishment.

Porpostoma guamensis n. sp., a philasterine scuticociliate associated with brown-band disease of corals.

Brown band disease of coral is caused by a ciliate that consumes the tissue of the corals in the genus Acropora. We describe the ciliate associated with this disease on Guam, based on: general morphology, division stages, and ciliature observed on live and protargol-stained specimens; modification of the oral structures between divisional stages, observed on protargol-stained specimens; and some aspects of behavior in field and laboratory studies. Porpostoma guamensis n. sp. is elongate and has ciliature typical for the genus; live cells are 70-500 × 20-75 µm; the macronucleus is sausage-like, elongate but often bent, positioned centrally along the main cell axis; the oral ciliature follows a basic pattern, being composed of three adoral polykinetidal regions, as described for other species in the genus, although there is variability in the organization, especially in large cells where the three regions are not easily distinguished. Ciliates fed on coral with their oral region adjacent to the tissue, which they engulfed, leaving the coral a bare skeleton. Both zooxanthellae and nematocysts from coral occurred in the ciliates. Zooxanthellae appeared to be ingested alive but deteriorated within 2-3 days. Ciliates formed thin-walled division cysts on the coral and divided up to 3 times. Cysts formed around daughter cells within cysts. We provide some observations on the complex division pattern of the ciliate (i.e. tomont-trophont-cyst) and propose a possible complete pattern that requires further validation.

Resilience of coral-associated bacterial communities exposed to fish farm effluent.

BACKGROUND: The coral holobiont includes the coral animal, algal symbionts, and associated microbial community. These microbes help maintain the holobiont homeostasis; thus, sustaining robust mutualistic microbial communities is a fundamental part of long-term coral reef survival. Coastal pollution is one major threat to reefs, and intensive fish farming is a rapidly growing source of this pollution. METHODOLOGY & PRINCIPAL FINDINGS: We investigated the susceptibility and resilience of the bacterial communities associated with a common reef-building coral, Porites cylindrica, to coastal pollution by performing a clonally replicated transplantation experiment in Bolinao, Philippines adjacent to intensive fish farming. Ten fragments from each of four colonies (total of 40 fragments) were followed for 22 days across five sites: a well-flushed reference site (the original fragment source); two sites with low exposure to milkfish (Chanos chanos) aquaculture effluent; and two sites with high exposure. Elevated levels of dissolved organic carbon (DOC), chlorophyll a, total heterotrophic and autotrophic bacteria abundance, virus like particle (VLP) abundances, and culturable Vibrio abundance characterized the high effluent sites. Based on 16S rRNA clone libraries and denaturing gradient gel electrophoresis (DGGE) analysis, we observed rapid, dramatic changes in the coral-associated bacterial communities within five days of high effluent exposure. The community composition on fragments at these high effluent sites shifted towards known human and coral pathogens (i.e. Arcobacter, Fusobacterium, and Desulfovibrio) without the host corals showing signs of disease. The communities shifted back towards their original composition by day 22 without reduction in effluent levels. SIGNIFICANCE: This study reveals fish farms as a likely source of pathogens with the potential to proliferate on corals and an unexpected short-term resilience of coral-associated bacterial communities to eutrophication pressure. These data highlight a need for improved aquaculture practices that can achieve both sustainable industry goals and long-term coral reef survival.

Functionally diverse reef-fish communities ameliorate coral disease.

Coral reefs, the most diverse of marine ecosystems, currently experience unprecedented levels of degradation. Diseases are now recognized as a major cause of mortality in reef-forming corals and are complicit in phase shifts of reef ecosystems to algal-dominated states worldwide. Even so, factors contributing to disease occurrence, spread, and impact remain poorly understood. Ecosystem resilience has been linked to the conservation of functional diversity, whereas overfishing reduces functional diversity through cascading, top-down effects. Hence, we tested the hypothesis that reefs with trophically diverse reef fish communities have less coral disease than overfished reefs. We surveyed reefs across the central Philippines, including well-managed marine protected areas (MPAs), and found that disease prevalence was significantly negatively correlated with fish taxonomic diversity. Further, MPAs had significantly higher fish diversity and less disease than unprotected areas. We subsequently investigated potential links between coral disease and the trophic components of fish diversity, finding that only the density of coral-feeding chaetodontid butterflyfishes, seldom targeted by fishers, was positively associated with disease prevalence. These previously uncharacterized results are supported by a second large-scale dataset from the Great Barrier Reef. We hypothesize that members of the charismatic reef-fish family Chaetodontidae are major vectors of coral disease by virtue of their trophic specialization on hard corals and their ecological release in overfished areas, particularly outside MPAs.

Coral disease in Micronesian reefs: a link between disease prevalence and host abundance.

Current information regarding the effects of coral diseases on Indo-Pacific reefs lags behind that of the Caribbean. Considering that these reefs are geographically widespread, speciose, often highly influenced by human coastal populations, and inadequately monitored, developing a baseline database is a primary management issue for local scientists. In a first attempt to quantify diseases in Micronesia, Guam reefs were assessed for disease prevalence, host abundance, and community structure. Surveys of 15 reefs revealed 6 disease states affecting 8 families of reef-building corals and highly variable prevalence between sites, ranging from 0.2 to 12.6%. Guam reefs are taxonomically diverse but dominated by the genus Porites. Coral generic host abundance showed a significant and positive link with total disease prevalence. Five out of 6 of the observed disease states affected Porites spp. (mean prevalence within the genus: 6.14 +/- 0.88%), and acroporids and pocilloporids also showed high susceptibility. As the coral genera currently most affected by diseases are those providing the most structure to Guam's reefs, disease has the potential to have significant long-term effects, highlighting an urgent need for proactive management.

Influence of marine reserves on coral disease prevalence.

Predicted increases in disease with climate warming highlight the need for effective management strategies to mitigate disease effects in coral communities. We examined the role of marine protected areas (MPAs) in reducing disease in corals and the hypothesis that the composition of fish communities can influence coral health, by comparing disease prevalence between MPA and non-protected (control) reefs in Palau. Overall, the prevalence of diseases pooled, as well as the prevalence of skeletal eroding band (SEB), brown band disease (BrB) and growth anomalies (GAs) individually in major disease hosts (families Acroporidae and Poritidae), were not significantly reduced within MPAs. In fact, the prevalence of SEB was 2-fold higher within MPAs overall; however, the 4 studied MPAs were ineffective in enhancing coral assemblage or fish stock health. A negative association between the prevalence of SEB and richness of a fish species targeted by fishers in Palau highlights the potential role that well-managed MPAs could play in reducing SEB. The composition of coral communities and their susceptibility to bleaching also influenced the prevalence of disease on the studied reefs. The prevalence of diseases pooled and SEB were positively associated with the cover of major disease hosts (families Acroporidae and Poritidae), and the prevalence of BrB and bleaching were also positively associated. Although our study did not show positive effects of MPAs on coral heath, we did identify the potential for increased fish diversity within MPAs to reduce coral disease. Our study also highlights the complexity of relationships between fish assemblages, coral community composition and coral health on Indo-Pacific reefs.

Coral diseases on Philippine reefs: genus Porites is a dominant host.

While it is generally assumed that Indo-Pacific reefs are not widely affected by diseases, limited data suggest a number of diseases and syndromes that appear to differ from those currently under study in the Caribbean. This report presents the results of a baseline survey of coral diseases in 2 regions in the Philippines: the Central Visayas and the Lingayen Gulf. Mean prevalence for all diseases observed was 8.3 +/- 1.2% (mean +/- SE; n = 8 reefs), with Central Visayas reefs showing higher disease prevalence (11.6 +/- 2.8%; n = 4 reefs) than those of Lingayen Gulf (5.1 +/- 1.4%; n = 4 reefs). Five diseases and syndromes were described; 3 of these-Porites ulcerative white spot disease (PUWS) (prevalence = 8.96 +/- 2.2%), tumors (prevalence = 1.0 +/- 0.5%) and pigmentation response (prevalence = 0.5 +/- 0.2%)--occurred frequently in both regions and targeted the genus Porites. Correlation between disease prevalence and number of Porites colonies was fairly strong (r2 = 43.4), though not significant, and no correlation was seen between prevalence and either the amount or diversity of hard coral. Porites is a major reef-builder in the Indo-Pacific comprising 30% of hard coral colonies on our surveyed reefs, and is generally thought to be a hardy, long-lived genus. Diseases targeting this robust group present an as yet unquantified risk to Philippine reefs and could result in major changes in reef structure.