9402186 HASSETT Due to the dramatic and sometimes catastrophic consequences of red tides, toxic dinoflagellates have been intensively studied over the years. However, relatively few of these studies have dealt with effects of dinoflagellates on zooplankton. The main objective of this project is to determine how the dinoflagellates, Alexandrium tamarensis and Scrippsiella trochoidea act upon the copepod digestive system and metabolism. These studies will examine if different copepod species have different susceptibilities and how these relate to feeding history and nutritional status, and will determine if other dinoflagellate species have similar impacts on copepods. This project will use visual description and morphometric analyses of the gut cells of several copepods feeding upon the 2 species of dinoflagelattes in laboratory experiments. Analyses of gut morphology will be conducted at both the light and electron- microscope level , and also will include observations of the digestive system of live copepods under light microscope. Changes in physiological rates (digestive enzyme activities, metabolic enzyme activities, excretion rate, and respiration rate) and feeding rate also will be determined to assess the consequences of ingesting a toxic dinoflagellate or of being exposed to dinoflagellate toxins. After establishing the interactions between copepods and the two dinoflagellates, this project will use the knowledge gained as a basis for a survey of impacts of other dinoflagellate species on copepods.
