Spatial variations

The purpose of this research was to determine the level of defensive aggression of the threespot damselfish, Stagastes planifrons, when exposed to intruders of different species using models. Adult S. planifrons were exposed to models of a conspecific, an herbivorous fish, Sparisoma viride, and a predator, Aulostomus maculatus. Attack rates and retreat rates of S. planifrons were determined by observations during exposure to models. It was expected that aggression levels would be highest towards the conspecific model and lowest towards the predator model and that evasive behavior would be highest in the presence of the predator model and lowest with the conspecific. It was found that there is a significant difference in the level of aggression when encountering a predator versus a conspecific, showing more aggression towards the conspecific and more evasion towards the predator. No significant difference was found in the aggression levels shown between the predator and the herbivore. Exposure to the predator elicited the highest number of retreats, also showing a significant difference in the level of evasion when comparing all three models. The results suggest that S. planifrons are able to differentiate between intruder species and react depending on the level of threat posed and perhaps on what is most energy efficient.

This student research was retrieved from Physis: Journal of Marine Science III (Spring 2008)19: 13-18 from CIEE Bonaire.

Mimetism allows organisms to blend into the environment and avoid detection by both predators and prey. The Atlantic trumpetfish, Aulostomus maculatus, uses three color morphologies blue, brown, and yellow to achieve this goal. The various colorations allow A. maculatus to stalk prey individuals and blend into tall gorgonians and sponges on the seafloor. Chromatophore and energy expenditure analysis showed these three morphs as steady and evenly dispersed. The present study focuses on behavioral and spatial differences between individuals of varying morphologies on a fringing reef in Bonaire, Dutch Caribbean. Length of trumpet fish, depth, and substratum association were noted on twelve 30-minute timed swims at varying depths and locations near Yellow Sub dive site. Results show no significant difference between the three morphology abundances, or between depth and color morphology. Only comparisons between brown and blue color morphologies were found to be significantly different with larger brown individuals and smaller blue individuals. Associations were found to be highest with sea-rods. Higher percentages of yellow color morphs associated with corals while more blue individuals tended to shadow fish. Brown morphs were found to have higher association rates overall which may account for their larger size. Trumpetfish that were not associated with one benthic substrate due to movement or hunting were considered to be active individuals. A difference in activity levels of the three color morphologies was not found to be statistically significant. Further research may include more investigation into the trumpetfish life history, and trumpetfish may serve as a model for color morphology studies in the marine environment.

This student research was retrieved from Physis: Journal of Marine Science XII (Fall 2012)19: 39-44 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.

Abstract:

Sponges are major epibionts of mangrove roots in the Caribbean. Mangrove sponge communities in the Caribbean mainly consist of species that are typical to this habitat and community compositions often differ from those found on coral reefs nearby. Heterogeneity in species distributions between locations and within locations between roots is often reported. This study quantifies the diversity and abundance of mangrove associated sponges in the inner bays of Curaçao and Aruba and correlates variability of regional sponge diversity with environmental variables measured along the surveyed sites. Tannin concentrations vary between mangrove roots, and were correlated to sponge cover as a possible cause for habitat heterogeneity on a smaller scale. A total of 22 species was observed. Heterogeneity in species richness and abundance was apparent, and several sponge species were restricted in their depth of occurrence. Statistical data reduction suggests that sponge diversity may be partly explained by the distance towards adjacent reefs and to the degree of eutrophication, in which the latter is comprised of rate of planktonic respiration, total carbon and turbidity. Tannin concentrations did not determine within locality species heterogeneity as a priori postulated, but were positively related to sponge cover for reasons not yet elucidated.