Using Knowledge of Chemical and Structural Defenses of Seaweeds to Develop a Standardized Measure of Herbivory in Tropical and Subtropical Habitats

Herbivory is an important process determining the structure and function of marine ecosystems, and this is especially true on coral reefs and in associated tropical and subtropical habitats where grazing by fishes can be intense. As reef degradation is occurring on a global scale, and overfishing can contribute to this problem, rates of herbivory can be an important indicator of reef function and resilience. Our goal was to develop a standardized herbivory assay that can be deployed globally to measure the impact of herbivorous fishes across multiple habitat types. Many tropical and subtropical seaweeds contain chemical and structural defenses that can protect them from herbivores, and this information was key to selecting a range of marine plants that are differentially palatable to herbivorous fishes for these assays. We present method development and experimental results from extensive deployment of these herbivory assays at Carrie Bow Cay, Belize.