dark band disease

Corals are frequently in competition with other benthic organisms, as space on the coral reef is highly sought after. With increased coral cover loss, and a possible coral-algal phase shift on reefs, competition between corals and other benthic organisms may become increasingly common. Competition between coral and other organisms, such as algae, other corals, and sponges may be a stressor for corals and possibly lead to increased disease prevalence and severity. Dark spot syndrome (DSS) is a highly prevalent disease in Bonaire and is found in the coral species Stephanocoenia intersepta and Siderastrea siderea. Some studies show that competition in corals increases their susceptibility to disease. This study investigates the correlation between coral competition and disease severity of dark spot syndrome in S. intersepta. One reason for this is that energy is allocated for competition rather than immune function and thus the coral’s ability to fight off disease is lowered. No significant correlation was found between the amount of competition (measured by the percent edge of the coral in competition) and the level of disease (measured by the percent of the coral with DSS). The mean disease level of all coral colonies is 2.56 (±0.34). There was also no correlation found between depth and severity of disease. Although no correlation was found, longer and more intensive studies are suggested to better understand the effect of competition on dark spot syndrome.

This student research was retrieved from Physis: Journal of Marine Science XIV (Fall 2013)19: 118-123 from CIEE Bonaire.

Corals are the building blocks of coral reefs as they provide countless marine organisms with protection and habitat. However, coral diseases are currently threatening coastal environments by causing tissue loss and, in some cases, death of corals. This destroys the habitats utilized by marine organisms and the biodiversity of given areas. Many factors contribute to the prevalence of coral diseases, but very little is known about the overall impact of anthropogenic stressors on diseases. Dark spots disease (DSD) is a common coral disease found in the Caribbean and was the subject of this study. Dark spots disease prevalence and severity was quantified utilizing video transects and a severity index approximately one kilometer north of downtown Kralendijk on the west coast of Bonaire, Dutch Caribbean. This data was then analyzed for any trends with regards to spatial location and depth. It was observed that DSD is typically more common and severe at deeper depths of 15 m than at shallower depths of 8 m, although no trends were observed in regards to spatial location and DSD distribution. Gaining a better understanding of DSD distribution paves the way for future studies to potentially understand causative agents of DSD; therefore, allowing for more preventative measures and mitigation processes to conserve the health of coral reefs.

This student research was retrieved from Physis: Journal of Marine Science XV (Spring 2014)19: 79-85 from CIEE Bonaire.

Environmental changes and deterioration have increased coral disease outbreaks, creating a Caribbean hot spot of high disease prevalence and virulence. Dark spots disease (DSD) has an unknown causative agent, although it is suspected to be a result of a biotic pathogen. Variation with anthropogenic stressors and DSD has been limited in research; therefore, the purpose of this study was to determine if a correlation existed between DSD prevalence and nutrient enrichment, in the form of nitrogen concentration. It was hypothesized that DSD prevalence and nitrogen concentration would be highest at shallower depths and that there would be a positive correlation between DSD prevalence and nitrogen concentration. In Kralendijk, Bonaire, sites were surveyed for DSD to calculate the prevalence and water samples were collected to determine the concentration of nitrogen. The results indicated no significant effect of depth and site on DSD prevalence as well as no significant effect of depth on nitrogen concentration. There was a significant effect of site on nutrient concentration as indicated by the significantly higher nitrogen concentration. The pooled data illustrated a weak positive relationship and correlation between DSD prevalence and nitrogen concentration with insignificant results, but one site illustrated a moderately strong positive relationship and correlation with statistical significance. The significant results at that site suggest some correlation between DSD prevalence and nitrogen concentration which requires further investigation ex situ to establish a stronger correlation or possible causation.

This student research was retrieved from Physis: Journal of Marine Science XV (Spring 2014)19: 36-44 from CIEE Bonaire.

In 2004, as part of a GEF funded project entitled “Coral Reef Targeted Research and Capacity Building” (CRTR), to assess the current status and future of these important communities, six groups of researchers looked at different aspects of the dynamics and degradation of coral reefs worldwide (i.e. Coral diseases, bleaching, connectivity, remote sensing. One of these groups, the Coral Disease Working Group (CDWG), assessed the number, prevalence, distribution, impacts and host range of coral diseases and their spatial and temporal variability in the wider Caribbean.

Curacao was selected as one of six localities spread over the Caribbean, and one of two southern localities. Results presented here represent our preliminary approach and surveys in Curacao. Surveys were done in permanently marked transects using the CARICOMP sampling protocol. Overall, coral diseases in these sites had, on average, a relatively low prevalence (5.74 ± 3.7%) at the community level (all colonies from all species included). Curacao was the second country with higher disease prevalence of the 6 countries visited across the Caribbean during the Summer-Fall of 2005, the weight of this prevalence coming from one of the two sites surveyed on the island. The most common diseases observed were dark spots syndrome (DSS), white plague type II (WP-II) and secondary infections by ciliates. Noteworthy was the lack of bleaching in these two reef localities and in general, in the Netherland Antilles when most of the eastern, northern and western were suffering the worst bleaching event on record for the Caribbean. Bleached colonies were only mild paling patterns and the overall prevalence was below 1.0 %. Octocoral diseases were almost two times more prevalent (9.6 ± 16.9%) than coral diseases in Curacao.