HOW DOES PARROTFISH AND URCHIN BIOEROSION IMPACT LIVE STAGHORN CORAL COVER ON A PATCH REEF IN BELIZE?

Bioerosion, the erosion of hard ocean substrates by living organisms, is an important process in developing the structure of coral reef framework. Sea urchins and parrotfish are two of the dominant bioeroders on Caribbean coral reefs, and their population sizes are often inversely correlated. Although the urchin species Echinometra viridis and Diadema antillarum eat macroalgae, which allows more space for coral growth on reef substrate, studies show that high densities of these urchins also can erode reefs to a point of threatening their health. When urchins are present in low densities or not present at all, parrotfish species such as Scarus iserti and Sparisoma viride are the dominant grazers of algae and bioeroders of coral substrate. Data were collected on live coral cover and abundance of urchins and parrotfish from five sites at Coral Gardens, Belize, a large Acropora cervicornis-dominated patch reef complex to examine the relationship between bioerosion rates and coral cover. Live coral cover of A. cervicornis (staghorn coral) patches at Coral Gardens is positively correlated with parrotfish CaCO₃ bioerosion rates and negatively correlated with urchin bioerosion rates. One site with uniquely high live coral cover (56.16%) also had the highest parrotfish bioerosion rate (1.54 kg/m²/year) and the lowest range of urchin CaCO₃ bioerosion (0.18 – 0.67 kg/m²/year). Sites with lower live coral cover (18.93 – 29.14%) were characterized by higher rates of bioerosion from urchins (83.24 – 168.07 kg/m²/year) and lower bioerosion rates from parrotfish (0.90 – 1.21 kg/m²/year). This suggests that while urchins are key reef community members, they can potentially erode the framework of a reef, which likely will reduce live coral cover.