Over the past two decades, HABs have not only increased in frequency and aerial extent, but have caused considerable economic loss and public health problems. A large majority of HABs are caused by dinoflagellates, which are often toxic, as seen in the Pfiesteria-related fish kills along the mid-Atlantic coast.

We propose a regional, comprehensive study of the physical, nutritional and trophodynamic mechanisms that contribute to blooms of Pfiesteria. We hypothesize that certain adaptive mechanisms are interdependent, and together contribute to the development and persistence of these blooms. Through comparative field and mesocosm experiments, spanning a rang of conditions under which Pfiesteria and other toxic Pfiesteria-like species are found to occur or to bloom, we will descrie the environmental conditions and factors that contribute to their success. Our laboratory and field results will be incorporated into an ecosystem model that can be used to predict the abundance of Pfiesteria in the mid-Atlantic region.