Dissertation Defense

Coral reefs are increasingly overgrown by algae and cyanobacteria that can inhibit coral growth and survival. Herbivores and detritivores play critical roles in controlling that overgrowth, but how species differ in their foraging targets and nutritional needs, and how their diets may shift as algae and cyanobacteria proliferate, are poorly understood. We developed PhycoRef, a curated 23S rRNA reference database for the molecular identification of algae and cyanobacteria. We applied this to evaluate how Caribbean parrotfishes, surgeonfishes, chubs, and a sea cucumber differ in their trophic roles, using a combination of behavioral observation, multi-marker DNA metabarcoding, and stable isotope analysis. We then assessed how foraging patterns and nutritional targets of the most locally abundant parrotfish (Scarus iseri) and surgeonfish (Acanthurus chirurgus) varied across five sites spanning broad gradients in coral, algae, and cyanobacterial cover. Finally, we compared how dietary exposure to heavy metals and agricultural pesticides differed among a parrotfish (S. iseri), surgeonfish (A. chirurgus), and sea cucumber (Holothuria mexicana) at sites with contrasting human impacts.