Bioeroding grazers, such as the sea urchin, Echinometra viridis, and parrotfish (Scaridae), play a vital role in maintaining the overall health of coral reef systems. At Coral Gardens, Belize, these organisms help to keep acroporid coral cover high and macroalgae cover low, sustaining an exceptionally healthy acroporid reef. In this study I hypothesized that there would be strong correlations between urchin densities and live coral or macroalgae cover. Using photoanalysis and in situ ecological surveys, I found that these relationships were not significant based on the data we collected. Past studies in the Caribbean, including Belize, discovered that there were strong relationships between these variables, so I concluded that our data was limited by our methods, specifically the two-dimensional photoanalysis. The high urchin densities at Coral Gardens, in comparison to similar studies, led me to suggest that not all of the macroalgae cover was accounted for through the photoanalysis, and that E. viridis lives in the crevices of Acropora cervicornis branches and finds enough food within the canopy of the coral.
Using standard bioerosion calculations for E. viridis and Scaridae, a gross carbonate bioerosion rate was determined for Coral Gardens. This rate, combined with the gross carbonate production rate for A. cervicornis at Coral Gardens, establishes that Coral Gardens is in a state of net carbonate accretion, or growth. However, our macroalgae percentages were most likely constrained by the photoanalysis, due to the unique branching coral habitat of A. cervicornis. Thus, the carbonate budget for Coral Gardens needs further analysis. Finally, gut content analysis is needed on E. viridis to determine the type of algae being consumed and the amount of CaCO3 that is being bioeroded by urchins at Coral Gardens.
Bender, Sarah K., "Grazer Dynamics on a Relict Acroporid Patch Reef System and Their Implications for the Carbonate Budget at Coral Gardens, Belize" (2015). Senior Independent Study Theses. Paper 6535.
Bachelor of Arts
Senior Independent Study Thesis
© Copyright 2015 Sarah K. Bender