Current Research and Research Interests

M.S. Thesis:

The effects of sea urchins on the coral reef community

Coral reefs are known for their exceptional species diversity and productivity, yet are extremely sensitive to biotic and abiotic perturbations. Many reefs have experienced phase shifts as the result of alterations in herbivore abundance. This research in Moorea, French Polynesia, is aimed at elucidating differential effects of sea urchin species on the coral reef community. Preliminary quantifications of benthic reef components suggest that the tropical echinoids Diadema savignyi, Echinostrephus aciculatus and Echinometra mathaei influence the community on different scales, likely as a result of different feeding modes and grazing intensities. On a small, 25-cm2 scale, E. mathaei abundance was correlated positively with cover of crustose coralline algae, while E. aciculatus was associated with cover by algal turfs and macroalgae. On a larger scale (> 1 m2), it may be possible to predict reef community structure based on echinoid communities.

In order to test the hypothesis that diadematids are more effective than other echinoids in limiting macroalgal abundance, echinoid species on coral heads will be manipulated and macroalgal recruitment and growth quantified. The differential ability of echinoids to initiate and reverse phase shifts on already established communities will be tested by manipulating densities and compositions of echinoid species on coral heads dominated by either macroalgae, algal turfs or coral. Community structure trajectories will be quantified over time through the assessment of percent cover of macroalgae, crustose coralline algae, turf and live coral. The results of this study will elucidate the ecological importance of species-specific interactions that shape reef communities.