This dissertation research consists of three projects focusing on landscape-scale effects of macroconsumers (fish, freshwater shrimp) on Puerto Rico streams. Project one takes advantage of a natural experiment and examines upstream effects of dams on ecosystem properties due to extirpation of migratory macroconsumers. Project two uses macroconsumer exclusion experiments to examine whether small-scale manipulations predict effects of large-scale extirpation. Project three is a longitudinal survey of the last undammed main stem river draining the Caribbean National Forest and investigates natural variation in macroconsumer distributions and the relevance of the River Continuum Concept to tropical islands. All three projects examine standing stocks of epilithic fine and coarse particulate organic matter, fine particulate inorganic matter, and algal and insect biomass. The broader significance of this research includes direct contributions to conservation of tropical streams by extrapolating small-scale experiments to the larger scales at which humans affect watersheds, improving our understanding of the ecological importance of aquatic biota and documenting relatively pristine river conditions.
