Coral reefs are a source of food, tourism revenue and cultural pride for people in the United States and around the world, yet a suite of assaults including fishing, terrestrial runoff, sewage input, chemical pollution, global change and disease have pushed most coral reefs to the point of collapse. Individual corals grow extremely slowly, therefore future recovery of coral reefs will depend primarily on the successful sexual reproduction of the few corals that remain. In their larval stage, corals conduct complex swimming and searching behaviors to select their settlement locations. Previous work demonstrated that water column bacteria and antibiotic treatments alter the swimming rate and settlement rate, respectively, of lab-raised coral larvae. Therefore, interactions with bacteria are important for the successful completion of the coral life cycle. This project will use field collections during coral spawning, behavioral assays, and fluorescence-based microscopy to determine how coral larvae physically interact with bacteria and which of these interactions with bacteria are most important for normal larval behavior. The results of this research will help foster coral population recovery in Pacific and Caribbean reef ecoystems. The results will also add to the scientific understanding of animal reproduction and development, animal behavior, and interactions between animals and bacteria. During the project, at least two students will be trained in research diving and fieldwork methods, and at least one student will be trained in molecular biology and microscopy.