The population dynamics of these microscopic organisms, the relative amounts of different species, as well as abundances overall, have been shifting in the past 50 years as the climate changes, waters warm and cloudiness increases. In Narragansett Bay, the former abundant food source of the annual winter-spring diatom bloom has decreased or disappeared altogether in some years. Dinoflagellates previously dominated in the summer, but now diatoms have replaced them in short, often intense blooms leading to increased hypoxic, or low-oxygen, events in summer months. Understanding and predicting the abundance, distribution and diversity of plankton is critical to predicting their important function in global biogeochemical cycles, as well as helping us to understand and manage our fisheries resources.