Tropical Marine Ecology 2012

Tropical Marine Ecology 2012 - 5 Best Photos !

I put together a little video slideshow of the student-selected "best of" photos from this year's trip.

 

 

Enjoy!

Percent Coral Coverage - Laura and Billy

One of the transect photos used to identify the percent cover of different bottom types.

During the 1980’s-90’s there was a dramatic increase of macroalgal cover on Caribbean reefs, specifically Discovery Bay, Jamaica. This shift from coral to algal cover has been attributed to top-down control due to the reduction of herbivory by both the continuous overfishing of grazers (Acanthurids and Scarids) and the mass die off of Diadema antillarum in 1983-84. Since the return of D. antillarum in the late 1990s, a trend of reduced macroalgae began. Our study looks at the current phase state of the Discovery Bay reefs by measuring percent cover of coral, macroalgae, turf algae and coralline algae. Three sites were selected in Discovery Bay where 20 meter transects were run multiple times per site at depths of both 9 m and 18 m to assess benthic cover and potential variation with depth. Video transects were taken along each transect as well as counts of D. antillarum within one meter of the transect line to determine the presence or absence of herbivores in each transect. Data analysis supports a continued dominance of an algal phase state. Percent coral cover was 3-6 % compared to algal cover of 46.6 – 57.7 %. The reduced presence of D. antillarum in the study sites below 9 m may support the idea that decreased herbivory results in higher algal percent coverage and therefore lower coral coverage.

 

Material Coverage Preferences of Tripneustes ventricosus and Lytechinus variegatus - Susan and Bianca

Tripneustes ventricosus covering itself in natural and bendable materials.

Tripneustes ventricosus and Lytechinus variegatus have been known to cover themselves for a few reasons; avoidance of predation and protection from UV rays. It is thought that there may be a correlation between the use of materials that conform to the urchins’ body and its preferences for that material. For this paper, it was hypothesized that urchins are more likely to use a bendable natural material over materials that are not able to conform to their body shape. Samples of both these species were collected from two sites, mangroves and turtle grass, in Discovery Bay. Of these samples two were large for both species and two were smaller in size for each species collected. A total of 16 individuals were used to conduct this experiment. There were seven different conditions they were tested under; the use of natural bendable material, natural unbendable, unnatural bendable, unnatural unbendable, unnatural and natural bendable, unnatural and natural unbendable, and bendable and unbendable materials. Although the majority of the data was not statistically significant, there were some noted correlations. On average the larger sized urchins, of both species, used more material to cover themselves than the smaller sized urchins. T. ventricosus covered itself more than L. variegates, with a statistically significant difference when using unnatural, bendable materials (p=0.0095). The urchins collected from the mangroves used more materials for coverage than those from the turtle grass; statistically significant difference when using natural, bendable materials (p=0.008176). Although there is no statistical significance natural, bendable materials were used the most, while unnatural, unbendable materials were used to least.

 

 

 

Possible factors affecting predation of Ophioderma appressum and Ophiocoma enchinata - Stephanie and Nicole

A brittle star at the start of one of the time trials.

Two species of brittle stars that are abundant in the reef flat of Discovery Bay are Opidoderma appressum and Ophiocoma enchinata, commonly known as the Banded-Arm brittle star and the Blunt-Spined brittle star respectively. When threatened, these organisms use their long arms to quickly find cover. If they are caught they have the ability to detach their arms in order to escape. We hypothesized that Ophiocoma enchinata would have a faster escape rate because they tend to be larger than Opidoderma appressum. Our hypothesis was not correct. Our data showed that larger brittle stars were not necessarily faster than the smaller ones and there was no difference in velocity between the two species. However, we did find that there was a significant difference in velocity among the different color variants of Opidoderma appressum, which led us to believe that surface color may have an effect on the velocity. We hypothesized that the color variants would move faster on a lighter surface when compared to a darker surface. We found that the average velocity significantly increased when the brittle star was placed on a light surface compared to a dark surface. As a result, we hypothesized that Opidoderma appressum may have a color preference. We found no statistical significance that would support our hypothesis but our data for this experiment was skewed due to a lack of specimens.