Our enduring objectives have been to understand fundamental aspects of symbiotic dinoflagellate (Symbiodinium) distribution, acquisition and functionality in their cnidarian (coral, jellyfish and anemone) and molluscan (giant clam) hosts. We employ molecular, genetic, biochemical and physiological techniques to resolve how genotypic and geographic differences influence the distribution, host-specificity, environmental specialization of these organisms. We also pursue how changing environmental factors correlate with recent onslaughts of bleaching and death in coral reefs, the biomass of corals and density/chlorophyll/photosynthetic efficiency of Symbiodinium, and the use of carbon by corals and Symbiodinium living inside of cnidarians.