Local dynamics of a white syndrome outbreak and changes in the microbial community associated with colonies of the scleractinian brain coral Pseudodiploria strigosa.

Reef corals in the Mexican Reef System have been severely affected by the emergence of a white syndrome that resembles both White Plague II and SCTLD descriptions. Meandroid scleractinian coral species are among the most severely affected. To gain insight into this affliction we conducted a broad study in the brain coral Pseudodiploria strigosa at a rear reef site in the NE Mexican Caribbean. We describe macro and microscopical signals of the disease, characterize the outbreak dynamics, the tissue histopathology, explore immunological responses in the individuals, and compare microbial assemblages associated with the surface mucus layer of healthy and unhealthy colonies. At the study site, the white syndrome outbreak on P. strigosa showed a high incidence rate in summer-fall and a low one in winter, as well as low survival expectation of diseased colonies at the end of the study. After 306 days of observation, out of 96 tracked colonies, eight remained apparently healthy and seven were diseased. No effective resistance to colony disease progression was observed once white syndrome signs developed. Tissue loss rate during the study varied among colonies (mean = 10.8 cm2, s.d. = 7.8 cm2) suggesting a complex relation between causal agents and colony resistance. The deterioration of tissues was evidenced from the basal to the surface body wall of polyps (up to 66% hypertrophy and liquefactive necrosis in unhealthy colonies), implying that microscopic alterations begin before macroscopic signals develop, suggesting this may be a systemic disease. We measured high levels of phenoloxidase (two orders of magnitude higher PO activity than P. strigosa affected by BBD) and antibacterial activity without significant reduction in unhealthy samples from the mucus layer, indicative of an enhanced immunological response. Results showed that opportunistic bacteria dominated damaged colonies, where six genera of the Bacteroidia class were found with significant changes in unhealthy colonies after DeSeq2 analysis. Nevertheless, histological observations did not support infection of the tissues. The opportunistic overload seems to be contained within the mucus layer but may be associated with the mortality of tissues in a yet unclear way. Future research should focus on experimental infections, the tracking of natural infections, and the immunocompetence of corals in the face of environmental pressures due to local, regional, and global impacts. If environmental deterioration is the primary cause of the continuing emergence and re-emergence of lethal coral diseases, as has been proposed by many authors, the only true option to effectively help preserve the coral reef biodiversity and services, is to restore the environmental quality of reef waters at the local scale and reduce greenhouse gases at the global scale.

Systematic review and meta-analysis of 50 years of coral disease research visualized through the scope of network theory.

Coral disease research encompasses five decades of undeniable progress. Since the first descriptions of anomalous signs, we have come to understand multiple processes and environmental drivers that interact with coral pathologies. In order to gain a better insight into the knowledge we already have, we explored how key topics in coral disease research have been related to each other using network analysis. We reviewed 719 papers and conference proceedings published from 1965 to 2017. From each study, four elements determined our network nodes: (1) studied disease(s); (2) host genus; (3) marine ecoregion(s) associated with the study site; and (4) research objectives. Basic properties of this network confirmed that there is a set of specific topics comprising the majority of research. The top five diseases, genera, and ecoregions studied accounted for over 48% of the research effort in all cases. The community structure analysis identified 15 clusters of topics with different degrees of overlap among them. These clusters represent the typical sets of elements that appear together for a given study. Our results show that while some coral diseases have been studied considering multiple aspects, the overall trend is for most diseases to be understood under a limited range of approaches, e.g., bacterial assemblages have been considerably studied in Yellow and Black band diseases while immune response has been better examined for the aspergillosis-Gorgonia system. Thus, our challenge in the near future is to identify and resolve potential gaps in order to achieve a more comprehensive progress on coral disease research.

Genotypic assessment of a dichotomous key to identify Vibrio coralliilyticus, a coral pathogen.

Vibrio coralliilyticus is a known pathogen to corals and larvae of bivalves. Its identification is made based on phenotypic and genotypic characters of isolated strains. To evaluate the efficiency of the phenotypic identification, 21 strains identified as V. coralliilyticus using a widely used dichotomous key were analyzed by qualitative PCR and sequencing of the 16S rDNA region. The results obtained by the behavioral test, amino acids usage, allow us to distinguish 3 A/L/O profiles: (1) A+/L-/O+; (2) A+/L+/O+; and (3) A-/L+/O+. In the genotypic tests, all strains tested positive with primers specific for the Vibrio genus. However, when primers were used for species identification, the results did not match those obtained with the dichotomous key chosen. The phenotypic characteristics taken into account to set apart V. coralliilyticus and other species were not proven to be efficient. More information about the morphological diversity of colonies and enzymatic activities should be considered in the formulation of phenotypic keys for V. coralliilyticus and related species.

The effects of a coral disease on the reproductive output of Montastraea faveolata (Scleractinia: Faviidae)

The direct impacts of coral diseases on coral populations have been assessed by quantifying coral tissue loss and colony mortality, but the determination of the indirect effects of diseases, such as disruptions in life history functions (e.g. reproduction, growth and maintenance), are more difficult to ascertain and have been scant. This study involved a comparison of various measures of reproductive output from histological slides of healthy tissue samples of Montastraea faveolata and tissue samples from colonies with white plague (WP) infections in Dominica (West Indies). Although the variability in the reproductive data was high, WP had significant negative impacts on the percentage of reproductive polyps per cm2, the percentage of reproductive mesenteries within a polyp, oocyte quantity per polyp, mean oocyte volume (mm3), and fecundity (oocyte volume per cm2 of tissue). However, these effects were only observed in the tissue directly impacted by the WP disease "band" and were not observed in tissue samples taken 20 cm away from the lesion. Therefore, the effects of a coral disease (WP) on reproductive output are localized and not expressed colony-wide. Rev. Biol. Trop. 58 (Suppl. 3): 99-110. Epub 2010 October 01.

White plague-like coral disease in remote reefs of the Western Caribbean

The health of coral reef communities has been decreasing over the last 50 years, due the negative effects of human activities combined with other natural processes. We present documentation of a White Plague Disease (WPD) outbreak in the Serrana Bank, an isolated Western Caribbean atoll with presumably inexistent pollutant inputs from local human settlements. In addition, this study summarizes seven years of observations on diseased corals in the nearby island of San Andrés, which in contrast is one of the most populated islands of the Caribbean. There was a massive coral mortality in the atoll lagoon (14°27’53.24", 80°14’22.27" W, and 12m depth) due to WPD on May 4 of 2003. Seventeen species were found dead or largely affected by the disease. The information resulting from GPS and manta-tow transects revealed that approximately 5.8ha of reticulate Montastraea spp. patch reefs were lethally affected by the disease in the atoll. On May 8 of the same year we observed and calculated a mean coral cover of 7.03% (SD± 2.44), a mean diseased coral tissue cover of 5.5% (SD± 1.1) and a 13.4% (SD± 8.05) of recently dead coral covered with a thin filamentous algae layer; approximately 73% of mortalities caused by the disease occurred before the end of the outbreak. A rough estimate of 18.9% in recent coral cover reduction can be attributed to WPD. This represents about 82% of the total coral cover decline since 1995. Semi-enclosed environments such as atoll lagoons and the reticulate patch-reefs of Montastraea spp. seem to be particularly vulnerable to this kind of coral disease, which constitute an alert to increase the monitoring of the same kind of atoll environments. The WPD has been present in the area of the nearby island of San Andrés at a low prevalence level, with sporadic increasing peaks of disease proliferation. The peaks observed during 1999 and 2004 comprised increases of 266% and 355% respectively, suggesting an alarming progression of the disease in this area. This study includes new information of the epizoolotiology of White Plague Disease and documents the permanent prevalence and progression of the WPD in the area of San Andres Island. Rev. Biol. Trop. 58 (Suppl. 1): 145-154. Epub 2010 May 01.

Este trabajo presenta datos sobre un brote de la Enfermedad de Plaga Blanca (EPB) en el banco de Serrana y resume siete años de observaciones de esta enfermedad en la vecina isla de San Andrés (Caribe colombiano). La mortalidad masiva de corales por causa de EPB se observó en la laguna del atolón (14° 27’ 53.24", 80° 14’ 22.27" W, y 12m de profundidad) en mayo 4 de 2003. Se encontraron 17 especies muertas o atacadas por EPB y 5.8Ha de parches de Montastraea spp. fueron letalmente afectadas por la enfermedad. En mayo 8 del mismo año observamos y calculamos una cobertura promedio de coral de 7.03% (SD± 2.44), un promedio de tejido coralino enfermo de 5.5% (SD± 1.1) y un 13.4% (SD± 8.05) de coral recientemente muerto cubierto con una fina capa de algas filamentosas; aproximadamente 73% de la mortalidad a causa de la enfermedad ya había ocurrido antes de que terminara el brote de EPB. La EPB ha estado presente en el área de la vecina isla de San Andrés con un bajo nivel de prevalencia pero con esporádicos picos de proliferación de la enfermedad. Durante 1999 y 2004 se observaron incrementos de prevalencia de 266% y 355% respectivamente. Ambientes semi-cerrados como son las lagunas de los atolones y los arrecifes de parche reticulados de Montastraea spp. parecen ser especialmente vulnerables a este tipo de enfermedades coralinas, lo que constituye una alerta hacia una mayor atención y monitoreo en este tipo de ambientes lagunares en atolones.

The recent decline of Montastraea annularis (complex) coral populations in western Curaçao: a cause for concern? / La reciente disminución de las poblaciones de coral Montastraea annularis (complejo) en el oeste de Curazao: ¿un motivo de preocupación?

Shallow leeward reefs off the western end of Curaçao are dominated by extensive populations of M. annularis (complex). These species are larger in size (mean= 66 cm diameter) than all other species, with few small colonies (<30 cm) and notable absence of recruits. In 1998, colonies of M. annularis (complex) accounted for more then 45% of all species >10 cm observed within transects, and most exhibited low levels of partial mortality (mean= 22.5%). These species were less abundant (38% of all colonies) in 2005. Partial mortality among live colonies of M. annularis and M. faveolata increased by 85% (mean = 42% partial mortality) and numerous dead colonies of M. faveolata and M. annularis were observed; M. franksi colonies were generally in excellent condition (14% partial tissue mortality). A high prevalence of coral diseases (3-30%) was documented among M. annularis and M. faveolata, while all other species were less frequently affected. Yellow band disease (YBD) emerged shortly after the 1995 bleaching event, and rapidly spread throughout all depths, with the highest prevalence between 1997-1999. YBD caused slow rates of mortality (=1 cm/month), but multiple focal lesions appeared on individual colonies, and these progressively radiated outward as they killed the colonies. By 2005, 44% of the tagged corals were dead; the remainder exhibited active YBD infections (21%) or were in remission (31.6%) but were missing on average >90% of their tissue. Although the incidence of YBD has declined since 2000, white plague (WP) prevalence was unusually high (4-12%) in 2001 and 2005, with affected colonies exhibiting recent mortality of up to 70%. Dead Montastraea spp. surfaces are being colonized by other corals, including poritids, agaricids, and other faviids, while recruits of M. annularis (complex) are absent. If diseases and other biotic stressors persist on these reefs, M. annularis and M. faveolata populations may undergo a decline similar to that observed in the 1980s among Caribbean acroporids. Rev. Biol. Trop. 54 (Suppl. 3): 45- 58. Epub 2007 Jan. 15.

Los arrecifes someros a sotavento del oeste de Curaçao están dominados por extensas poblaciones de Montastraea annularis (complejo). Estas especies son mayores en tamaño (promedio= 66 cm de diámetro) que las otras especies, con algunas colonias pequeñas (<30 cm) y una notable ausencia de reclutas. En 1998, las colonias de Montastraea annularis (complejo), representaban más del 45% de todas las especies de >10 cm observadas en transectos y la mayoría exhibió bajos niveles de mortalidad parcial (prom= 22.5%). En el 2005, fueron menos abundantes (38% de las colonias). La mortalidad parcial en colonias vivas de M. annularis y M. faveolata se incrementó en un 85% (promedio= 42% de mortalidad parcial) y se observaron numerosas colonias de M. annularis y M. faveolata muertas; las colonias de M. franski generalmente se encontraron en excelentes condiciones (14% de mortalidad parcial). Se documentó una alta prevalencia de enfermedades de coral (3-30%) en M. annularis y M. faveolata, mientras que las otras especies se vieron afectadas con menor frecuencia. La enfermedad de banda amarilla (BA) emergió poco después del blanqueamiento de 1995 y se dispersó rápidamente en todas las profundidades, alcanzando su mayor prevalencia entre 1997-1999. La BA causó mortalidades lentas (= 1cm/mes), con aparición de múltiples lesiones focales en colonias individuales; estas lesiones fueron creciendo progresivamente al tiempo que mataban las colonias. Para el año 2005, el 44% de los corales que se etiquetaron habían muerto; los restantes exhibían infecciones activas de BA (21%), o estaban en remisión (31.6%) pero habían perdido un promedio de >90% de su tejido. Aunque la incidencia de BA disminuyó a partir del 2000, la prevalencia de la plaga blanca (PB) fue inusualmente alta (4-12%) en el 2001 y 2005, provocando mortalidades recientes de hasta un 70% en las colonias afectadas. Las superficies muertas de Montastraea spp. han sido colonizadas por otros corales, incluyendo porítidos, agarícidos y otros fávidos, mientras que continúa la ausencia de reclutas de M. annularis (complejo). Si las enfermedades y otros estresores bióticos persisten en estos arrecifes, las poblaciones de M. annularis y M. faveolata podrían decaer de forma similar a como lo hicieron los acropóridos del Caribe durante la década de 1980.

Status of aspergillosis and sea fan populations in Curaçao ten years after the 1995 Caribbean epizootic / Situación de las poblaciones de aspergilosis y abanicos de mar en Curazao diez años después de la epizootia del Caribe de 1995

In 1995, a survey of sea fan corals was conducted in Curaçao during a Caribbean-wide outbreak of the sea fan disease aspergillosis. The survey was repeated in 2005 using the same methodology and identical sites to examine changes in sea fan populations 10 years after the initial epizootic. Necrotic lesions typical of aspergillosis were present on as many sea fans in 2005 as in 1995 (mean ± SE: 52 ± 6 vs 43 ± 10%). The disease also showed no significant variation in virulence (9.6 ± 1.2 vs 8.8 ± 1.0% tissue loss per diseased colony). However, the average number of sea fan colonies per 10 m² decreased from 2.7 ± 1.1 to 0.7 ± 0.2 over the 10-year period, a decline of almost 75%. This decrease occurred for all colony sizes, but was more pronounced among small colonies, resulting in an overall trend of domination by large colonies. These results support that aspergillosis can have a significant, long-term impact on sea fan population size and structure. The continued presence of the disease in 2005 could be contributing to reduced recruitment and/or selective mortality among the smallest colonies. This study provides no indication that host resistance against aspergillosis could reverse the decline of Caribbean sea fan corals. Rev. Biol. Trop. 54 (Suppl. 3): 153-160. Epub 2007 Jan. 15.

En 1995, se realizó un sondeo de los abanicos de mar durante un brote de aspergilosis, una enfermedad de abanicos de mar extendida en todo el Caribe. En el año 2005 se repitió el sondeo utilizando exactamente la misma metodología y los mismos sitios para examinar cambios en las poblaciones tras 10 años del inicio del brote. Se presentaron lesiones necróticas típicas de la aspergilosis en tantos abanicos en el 2005, como en 1995 (promedio ± ES: 52 ± 6 vs 43 ± 10%). La enfermedad tampoco mostró variaciones significativas en la virulencia (9.6 ± 1.2 vs 8.8 ± 1.0%, pérdida de tejido por colonia enferma). Sin embargo, el número promedio de colonias de abanico de mar por cada 10 m² bajó desde 2.7 ± 1 hasta 0.7 ± 0.2 en este período de 10 años, una disminución de casi 75%. Este decrecimiento ocurrió en colonias de todo tamaño, pero fue más pronunciado en colonias pequeñas, produciendo una tendencia general de dominancia de colonias grandes. Estos resultados apoyan la idea de que la aspergilosis puede tener un impacto significativo a largo plazo en el tamaño y estructura poblacional de los abanicos de mar. La continuidad en la presencia de la enfermedad en el 2005 puede estar contribuyendo a la reducción en el reclutamiento y/o a la mortalidad selectiva de las colonias más pequeñas. Este estudio no provee ninguna evidencia de que la resistencia del hospedero contra la aspergilosis pueda revertir el decrecimiento de los abanicos de mar en el Caribe.