Aldo Cróquer

Spatial variability in distribution and prevalence of Caribbean scleractinian coral and octocoral diseases. I. Community-level analysis

Geographic assessments of coral diseases are needed to understand their local and geographic spatial-temporal variability. Coral and octocoral diseases and their prevalence were assessed along 4 permanent 10 x 2 m band-transects in each of 3 depth habitats (<4, 5-12 and >15 m) in each of 2 reefs in each of 6 countries across the wider Caribbean during the summer and fall of 2005. A permutational multivariate analysis of variance was used to test variability of major diseases and community level disease prevalence in corals and octocorals among habitats, reefs and countries. The most common and damaging diseases reported for the region were found in most reefs surveyed, but prevalence at the community level was generally low (ca. 2%) increasing from northern to southern latitudes. A significant interaction between sites (nested within country) and depth habitats was found (F = 2.1, df = 12, p = 0.02), with higher prevalence of coral diseases in deep habitats of Culebrita, Puerto Rico (14.8 +/- SE 6.5%) and in shallow habitats of Roldán, Panama (10.2 +/- SE 3.5%). The relative importance of each particular disease was dependent on site and habitat (depth intervals) (F = 1.7, df = 12, p = 0.001), with black band disease more prevalent in shallow habitats of Ritas, Bermuda (1.7 +/- SE 0.4%) and yellow band disease (YBD) more prevalent in deeper habitats of Chub Cut, Bermuda (3.7 +/- SE 0.5%). There was a significant interaction of total octocoral diseases with country and habitat (F = 2.8, df = 10, p = 0.04) with higher prevalence in deeper habitats of Curaçao (25.9 +/- SE 4.2%). Our results indicate that patterns of prevalence of coral and octocoral diseases were not consistent across the different spatial scales, showing differences produced by particular diseases and community composition present. There were no widespread epizootics, but local white plague-II and YBD epizootics were observed in Puerto Rico and other localities.

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.

Changes in Caribbean coral disease prevalence after the 2005 bleaching event.

Bleaching events and disease epizootics have increased during the past decades, suggesting a positive link between these 2 causes in producing coral mortality. However, studies to test this hypothesis, integrating a broad range of hierarchical spatial scales from habitats to distant localities, have not been conducted in the Caribbean. In this study, we examined links between bleaching intensity and disease prevalence collected from 6 countries, 2 reef sites for each country, and 3 habitats within each reef site (N = 6 x 2 x 3 = 36 site-habitat combinations) during the peak of bleaching in 2005 and a year after, in 2006. Patterns of disease prevalence and bleaching were significantly correlated (Rho = 0.58, p = 0.04). Higher variability in disease prevalence after bleaching occurred among habitats at each particular reef site, with a significant increase in prevalence recorded in 4 of the 10 site-habitats where bleaching was intense and a non-significant increase in disease prevalence in 18 out of the 26 site-habitats where bleaching was low to moderate. A significant linear correlation was found (r = 0.89, p = 0.008) between bleaching and the prevalence of 2 virulent diseases (yellow band disease and white plague) affecting the Montastraea species complex. Results of this study suggest that if bleaching events become more intense and frequent, disease-related mortality of Caribbean coral reef builders could increase, with uncertain effects on coral reef resilience.

Yellow band disease compromises the reproductive output of the Caribbean reef-building coral Montastraea faveolata (Anthozoa, Scleractinia).

Sexual reproduction is critical to coral population dynamics and the long-term regeneration of coral reefs. Bleaching, disease, and/or anthropogenic-induced tissue/colony loss reduce reproductive output. This is the first attempt to explore the effect of a biotic disease on the reproduction of scleractinian corals. The study aimed to assess the effect of yellow band disease (YBD) on the reproduction of the important Caribbean reef-builder Montastraea faveolata. Tissue samples were collected from diseased, transition, and healthy-looking areas in each of 5 infected colonies and from 5 healthy controls in southwest Puerto Rico. The effect of disease-induced mortality was assessed by collecting samples from the edge and center of surviving small and large, healthy-looking tissue patches from large, previously infected tagged colonies. Fecundity was significantly lower in disease lesions compared to transition and healthy-looking tissues and the controls (99% fewer eggs). Fecundity in transition areas was significantly lower (50%) than in healthy-looking tissues in diseased colonies, which had 23% lower fecundity than control tissues. Although this fecundity drop was not statistically significant, it could indicate a systemic effect of YBD across the colony. Large and small patches had 64 and 84% fewer eggs than controls, respectively, and edge polyps had 97% fewer eggs than those in central control areas. Field observations of the spawning behavior of each tissue area corroborated the histological results. Our results indicate that YBD significantly compromises the reproductive output of M. faveolata, potentially reducing the fitness and consequently, the recovery of this important reef-building species on Caribbean coral reefs.

Temporal variability and impact of coral diseases and bleaching in La Parguera, Puerto Rico from 2003–2007

Abstract. Most coral reefs in the wider Caribbean have been showing alarming signs of decline in recent years. Coral diseases and bleaching were monitored seasonally from 2003 to 2007 using the modified CARICOMP protocol with a stratified design to assess spatial and temporal variability in community level coral disease prevalence (proportion of affected colonies) at six reefs along an inshore-offshore gradient in La Parguera, southwest coast of Puerto Rico. Temperature loggers were deployed in each reef to assess co-variation between disease prevalence and virulence, and temperature. Virulence was assessed in Montastraea faveolata by tagging colonies, marking diseased edges, photographing and following them through time. Overall, all major reef-building species and other common reef groups were variously affected by disease and bleaching. Eleven diseases affected up to 42 species of scleractinian corals, 5 octocorals, 2 hydrocorals, 3 zoanthids, 2 sponges and 2 crustose coralline algae. Bleaching affected 52 species of corals, 22 octocorals, 3 hydrocorals, 2 zoanthids and 3 sponges. The prevalence of the diseases compromised coral health and varied significantly between seasons within years as well as among reefs within years and across years for each reef. White plague, yellow band and bleaching were the most prevalent and damaging diseases. Three white plague, two yellow band outbreaks and three bleaching events of different intensities were observed during the five years of study. Yellow band disease increased in prevalence (from 4 % to 30%) and virulence (0.8 ± 0.2 to 3.9 ± 1.4 cm/month) over 6 years, becoming one of the most important agents of coral mortality. Higher disease prevalence was consistently found at the mid-shelf and shelf-edge reefs than in reefs closest to the shoreline. The combination of white plague disease outbreaks, the intensive bleaching of 2005 and the chronic yellow band caused an average 53 % of live coral tissue loss in four years, the highest coral mortalities ever recorded in southwest Puerto Rico.

Bacterial assemblages shifts from healthy to yellow band disease states in the dominant reef coral Montastraea faveolata.

Descriptions of microbial diversity in healthy and diseased corals are necessary first steps before further investigating the mechanisms that lead to coral pathology. This is the first study that characterizes the microbial associates from healthy corals to yellow band disease (YBD) lesions using two complementary screening techniques of bacterial 16S rRNA genes [amplified 16S ribosomal DNA restriction analysis (ARDRA) of clone libraries and denaturing gradient gel electrophoresis (DGGE)]. Both these techniques showed similar trends, namely a significant difference in the bacterial community and an increase in diversity from healthy to YBD diseased lesions. There was an increase in the number of sequences retrieved of potentially pathogenic bacteria in diseased tissues compared with healthy samples, most notably from the genus Vibrio. Furthermore, we also detected a number of known pathogenic bacteria within the natural healthy microbiota such as Vibrio carchariae and Vibrio harveyi, a result supporting previous studies, showing healthy corals have the ability to harbour these species.

Experimental antibiotic treatment identifies potential pathogens of white band disease in the endangered Caribbean coral Acropora cervicornis.

Coral diseases have been increasingly reported over the past few decades and are a major contributor to coral decline worldwide. The Caribbean, in particular, has been noted as a hotspot for coral disease, and the aptly named white syndromes have caused the decline of the dominant reef building corals throughout their range. White band disease (WBD) has been implicated in the dramatic loss of Acropora cervicornis and Acropora palmata since the 1970s, resulting in both species being listed as critically endangered on the International Union for Conservation of Nature Red list. The causal agent of WBD remains unknown, although recent studies based on challenge experiments with filtrate from infected hosts concluded that the disease is probably caused by bacteria. Here, we report an experiment using four different antibiotic treatments, targeting different members of the disease-associated microbial community. Two antibiotics, ampicillin and paromomycin, arrested the disease completely, and by comparing with community shifts brought about by treatments that did not arrest the disease, we have identified the likely candidate causal agent or agents of WBD. Our interpretation of the experimental treatments is that one or a combination of up to three specific bacterial types, detected consistently in diseased corals but not detectable in healthy corals, are likely causal agents of WBD. In addition, a histophagous ciliate (Philaster lucinda) identical to that found consistently in association with white syndrome in Indo-Pacific acroporas was also consistently detected in all WBD samples and absent in healthy coral. Treatment with metronidazole reduced it to below detection limits, but did not arrest the disease. However, the microscopic disease signs changed, suggesting a secondary role in disease causation for this ciliate. In future studies to identify a causal agent of WBD via tests of Henle–Kochs postulates, it will be vital to experimentally control for populations of the other potential pathogens identified in this study.

First report of folliculinid ciliates affecting Caribbean scleractinian corals

This is the first report of a ciliate of the genus Halofolliculina infecting hard coral species of six families (Acroporidae, Agaricidae, Astrocoeniidae, Faviidae, Meandrinidae and Poritidae) and milleporids in the Caribbean. Surveys conducted during 2004–2005 in Venezuela, Panama and México confirmed that this ciliate affects up to 25 scleractinian species. The prevalence of this ciliate at the coral community level was variable across sites, being most commonly found at Los Roques, Venezuela, and at Bocas del Toro, Panama (prevalence 0.2–2.5%), but rarely observed in the Mexican Caribbean. Ciliates were more prevalent within populations of acroporids (Acropora palmata, Acropora cervicornis and Acropora prolifera) in Los Roques. Recent observations also corroborate the presence of these ciliates in Curacao and Puerto Rico. Our observations indicate that ciliates affecting corals have a wider distribution than previously thought, and are no longer exclusively found in the Indo-Pacific and Red Sea.

Global environmental changes: setting priorities for Latin American coastal habitats

As the effects of the Global Climate Changes on the costal regions of Central and South Americas advance, there is proportionally little research being made to understand such impacts. This commentary puts forward a series of propositions of strategies to improve performance of Central and South American science and policy making in order to cope with the future impacts of the Global Climate Changes in their coastal habitats.

Characterisation of the bacterial and fungal communities associated with different lesion sizes of Dark Spot Syndrome occurring in the Coral Stephanocoenia intersepta

The number and prevalence of coral diseases/syndromes are increasing worldwide. Dark Spot Syndrome (DSS) afflicts numerous coral species and is widespread throughout the Caribbean, yet there are no known causal agents. In this study we aimed to characterise the microbial communities (bacteria and fungi) associated with DSS lesions affecting the coral Stephanocoenia intersepta using nonculture molecular techniques. Bacterial diversity of healthy tissues (H), those in advance of the lesion interface (apparently healthy AH), and three sizes of disease lesions (small, medium, and large) varied significantly (ANOSIM R  = 0.052 p<0.001), apart from the medium and large lesions, which were similar in their community profile. Four bacteria fitted into the pattern expected from potential pathogens; namely absent from H, increasing in abundance within AH, and dominant in the lesions themselves. These included ribotypes related to Corynebacterium (KC190237), Acinetobacter (KC190251), Parvularculaceae (KC19027), and Oscillatoria (KC190271). Furthermore, two Vibrio species, a genus including many proposed coral pathogens, dominated the disease lesion and were absent from H and AH tissues, making them candidates as potential pathogens for DSS. In contrast, other members of bacteria from the same genus, such as V. harveyii were present throughout all sample types, supporting previous studies where potential coral pathogens exist in healthy tissues. Fungal diversity varied significantly as well, however the main difference between diseased and healthy tissues was the dominance of one ribotype, closely related to the plant pathogen, Rhytisma acerinum, a known causal agent of tar spot on tree leaves. As the corals’ symbiotic algae have been shown to turn to a darker pigmented state in DSS (giving rise to the syndromes name), the two most likely pathogens are R. acerinum and the bacterium Oscillatoria, which has been identified as the causal agent of the colouration in Black Band Disease, another widespread coral disease.