Method of Measuring Dinoflagellate Grazing on Flagellate and Bacteria Communities

Dinoflagellates are a major taxa of phytoplankton that include many species that commonly form harmful algal blooms (HABs) throughout the world. A feature of dinoflagellate physiology that may contribute to their competitive success is their ability to grow mixotrophically. As primary producers and photoautotrophs, these organisms convert inorganic nutrients to organic compounds using sunlight. During blooms inorganic nutrients and light commonly become limited. The ability to grow heterotrophically may offer dinoflagellates a competitive advantage over strict autotrophs during blooms. Using a modification of a method used to measure zooplankton grazing rates, we measured grazing by dinoflagellates on co-occurring microbes, including heterotrophic flagellates and bacteria, in the Lafayette River, a tributary in the Chesapeake Bay estuary during non-bloom and bloom conditions. Initial results of these experiments using this method are presented here.