Relative Pigment Composition and Remote Sensing Reflectance of Caribbean Shallow-Water Corals.

Reef corals typically contain a number of pigments, mostly due to their symbiotic relationship with photosynthetic dinoflagellates. These pigments usually vary in presence and concentration and influence the spectral characteristics of corals. We studied the variations in pigment composition among seven Caribbean shallow-water Scleractinian corals by means of High Performance Liquid Chromatography (HPLC) analysis to further resolve the discrimination of corals. We found a total of 27 different pigments among the coral species, including some alteration products of the main pigments. Additionally, pigments typically found in endolithic algae were also identified. A Principal Components Analysis and a Hierarchical Cluster Analysis showed the separation of coral species based on pigment composition. All the corals were collected under the same physical environmental conditions. This suggests that pigment in the coral's symbionts might be more genetically-determined than influenced by prevailing physical conditions of the reef. We further investigated the use of remote sensing reflectance (Rrs) as a tool for estimating the total pigment concentration of reef corals. Depending on the coral species, the Rrs and the total symbiont pigment concentration per coral tissue area correlation showed 79.5-98.5% confidence levels demonstrating its use as a non-invasive robust technique to estimate pigment concentration in studies of coral reef biodiversity and health.

Spatial variability of disease incidence and mortality in the sea fan Gorgonia ventalina in Puerto Rico (Alcyonacea: Goorgoniidae)

Populations of the common sea fan (Gorgonia ventalina) were decimated by an aspergillosis outbreak throughout the Caribbean two decades ago. Since then, aspergillosis has been considered as the principal cause of mortality in sea fans. However, prevalence and presumably incidence of this disease have been declining in the Caribbean since the mid 1990s. Incidence indicates new cases of disease in previously healthy colonies, while prevalence indicates percent of diseased colonies at a given sample. Most coral disease studies use prevalence rather than incidence to assess the temporal dynamics of diseases. Nevertheless, conclusions based only on prevalence should be handled carefully to avoid misinterpretation. This study was carried out at six reefs in Eastern Puerto Rico. We monitored a total of 448 colonies to (1) obtain estimates of incidence and prevalence of disease and other types of lesions, and (2) to determine causes of sea fan mortality plus their spatial and temporal variation. Three transects (10x1m) were haphazardly placed at each study site. At each transect, every colony was numbered and photographed and its height measured to the nearest cm. Transects were monitored at six months intervals and health status of the colonies was recorded. Also, the colonies were divided into height classes (small, medium and large) for incidence, prevalence and mortality analyses. Incidence and prevalence of disease were low in all reefs, suggesting that disease currently plays a minor role in the regulation of sea fans populations. Detachment was the main cause of mortality, and size structure data suggest that recruitment may compensate for mortality rates in two of the reefs. Spatial differences in size structure and density may be related to environmental and physical characteristics at the reef scale that allow sea fans to reach a safe colony size. Rev. Biol. Trop. 60 (2): 517-526. Epub 2012 June 01.

Las poblaciones de abanicos de mar (Gorgonia ventalina) fueron diezmadas por una epidemia de aspergilosis que afectó gran parte del Caribe, hace más de dos décadas. Desde entonces, a la aspergilosis se le ha considerado como la causa principal de mortalidad en los abanicos de mar. Sin embargo, la prevalencia e incidencia de esta enfermedad han disminuido en el Caribe desde mediados de los años 90. La incidencia se mide como la aparición de nuevos casos de la enfermedad en colonias previamente sanas, mientras que, la prevalencia indica el porcentaje de colonias enfermas en una muestra. La mayoría de los estudios en enfermedades de corales utilizan la prevalencia, en lugar de incidencia para evaluar la dinámica temporal de las enfermedades. No obstante, las conclusiones basadas sólo en prevalencia se deben manejar con precaución, para así evitar interpretaciones erróneas al respecto. En este estudio, 448 colonias de abanicos de mar ubicadas en seis arrecifes al este de Puerto Rico fueron examinadas durante un año, con el fin de: (1) estimar la incidencia y prevalencia de aspergilosis y de otros tipos de lesiones, (2) determinar las causas de mortalidad en abanicos de mar, además de su variación espacial y temporal. Las colonias presentes a lo largo de tres transectos establecidos al azar (10x1m) fueron marcadas y fotografiadas en cada arrecife al inicio del estudio. También, se midió la altura para determinar la categoría de tamaño de cada colonia (pequeña, mediana o grande). Las colonias fueron seguidas a lo largo de un año, y en cada visita se registró su condición de salud. Los resultados indicaron que la incidencia y prevalencia de aspergilosis fueron bajas en todos los arrecifes, lo cual sugiere que actualmente la enfermedad desempeña un rol menor en la regulación de las poblaciones de abanicos. El desprendimiento fue la principal causa de mortalidad, y los datos de estructura de tamaño sugieren que el reclutamiento puede compensar por las tasas de mortalidad en dos de los arrecifes. Las diferencias en densidades y estructuras de tamaño de los abanicos entre los sitios de estudio, pueden estar influenciados por características abióticas propias de cada arrecife. Esto puede permitir que los abanicos de mar alcancen un tamaño seguro para la sobrevivencia de la colonia.

Phylogeography of the cosmopolitan fungus Aspergillus flavus: is everything everywhere?

Aspergillus flavus is one of the most common fungal eukaryotes on the planet. It is notorious for production of aflatoxins, for causing aspergillosis in humans and animals, and as an opportunistic pathogen of animals and plants. Its role in marine habitats is unclear. Until now, little phylogeographic structure has been detected for the species, except at very local scales, and it appears to fit the classic dictum of microbial biogeography: Everything is everywhere. Here we use genetic relationships among isolates to determine phylogeographic structure, mating types, and differences in preferences for: marine vs. terrestrial habitats, various substrates, and clinical vs. nonclinical environments. Phylogenetic relationships among isolates were estimated using amplified fragment length polymorphisms (AFLPs) and mating types were determined for a worldwide sample of A. flavus isolates from diverse substrates and geographic locations. All isolates composed a single population, with no significant differentiation of marine vs. terrestrial isolates, clinical vs. environmental isolates, or association with substrate or geographic origin. There was evidence for local dominance of a single clade, probably clonal in origin and short-lived. The proportion of mating types was 1:1, supporting the hypothesis of recombination in natural populations. However, a high proportion of clinical isolates were MAT1-1 (85%), suggesting that a gene linked to the MAT1-1 idiomorph could play a role in pathogenicity. This study suggests that a more appropriate description of the phylogeography of A. flavus is 'everything is everywhere, but not all the time.'

Spatial variability of disease incidence and mortality in the sea fan Gorgonia ventalina in Puerto Rico (Alcyonacea: Goorgoniidae).

Populations of the common sea fan (Gorgonia ventalina) were decimated by an aspergillosis outbreak throughout the Caribbean two decades ago. Since then, aspergillosis has been considered as the principal cause of mortality in sea fans. However, prevalence and presumably incidence of this disease have been declining in the Caribbean since the mid 1990s. Incidence indicates new cases of disease in previously healthy colonies, while prevalence indicates percent of diseased colonies at a given sample. Most coral disease studies use prevalence rather than incidence to assess the temporal dynamics of diseases. Nevertheless, conclusions based only on prevalence should be handled carefully to avoid misinterpretation. This study was carried out at six reefs in Eastern Puerto Rico. We monitored a total of 448 colonies to (1) obtain estimates of incidence and prevalence of disease and other types of lesions, and (2) to determine causes of sea fan mortality plus their spatial and temporal variation. Three transects (10x1m) were haphazardly placed at each study site. At each transect, every colony was numbered and photographed and its height measured to the nearest cm. Transects were monitored at six months intervals and health status of the colonies was recorded. Also, the colonies were divided into height classes (small, medium and large) for incidence, prevalence and mortality analyses. Incidence and prevalence of disease were low in all reefs, suggesting that disease currently plays a minor role in the regulation of sea fans populations. Detachment was the main cause of mortality, and size structure data suggest that recruitment may compensate for mortality rates in two of the reefs. Spatial differences in size structure and density may be related to environmental and physical characteristics at the reef scale that allow sea fans to reach a safe colony size.

Marine isolates of Aspergillus flavus: denizens of the deep or lost at sea?

Most fungal species from marine environments also live on land. It is not clear whether these fungi reach the sea from terrestrial sources as spores or other propagules, or if there are separate ecotypes that live and reproduce in the sea. The emergence of marine diseases has created an urgency to understand the distribution of these fungi. Aspergillus flavus is ubiquitous in both terrestrial and marine environments. This species is an opportunistic pathogen in many hosts, making it a good model to study the relationship between genetic diversity and specificity of marine fungi. In this study, an intraspecific phylogeny of A. flavus isolates based on Amplified Fragment Length Polymorphisms (AFLPs) was used to determine if terrestrial and marine isolates form discrete populations, and to determine if phylogeny predicts substratum specificity. Results suggest lack of population structure in A. flavus. All isolates may compose a single population, with no clade particular to marine environments.