Cascading effects of nutrients on macroalgae and herbivorous fish on coral reefs in Bonaire, Dutch Caribbean

The island of Bonaire has significant contamination from anthropogenic sources such as sewage and landfills, which can cause excess nutrients in groundwater that will eventually enter the ocean. Nutrients have been suggested to increase macroalgal growth. The amount of nutrients and abundance of herbivores play a key role in maintaining a healthy coral dominated reef system. The major objective of this study was to determine the health of Bonaire's reefs by assessing various bioindicators, evaluating bioacummulation of macroalgae, assessing the biocontrol mechanisms, and determining the presence of phase shifts. This study looked at the relationship of herbivorous fish, nitrogen content and abundance of macroalgae to make inferences regarding the overall health of the reef. Two study sites, Kas di Arte and Something Special, were chosen for research over the course of four weeks. Data collection included abundance of herbivorous fish, substrate composition and nutrient level in water and algae samples. No inferences could be determined from the nutrient tests due to the varying concentrations found in both water and macroalgae. The herbivorous fish abundance and macroalgae were found to be inversely proportional. This study is important to determine whether herbivorous fish or nutrient input control phase shifts on Bonaire's reefs and can aid in identifying similar issues in reefs all over the Caribbean.

This student research was retrieved from Physis: Journal of Marine Science XV (Spring 2014)19: 58-65 from CIEE Bonaire.