The Effects of Temperature, Irradiance, and Nitrogen on the Encystment and Growth of the Freshwater Dinoflagellatesperidinium Cinctumandp. Willeiin Culture (Dinophyceae)1

Effects of temperature, irradiance, and nitrogen availability on the encystment and growth of the freshwater dinoflagellatesPeridinium cinctumEhrenberg andPeridinium willeiHuitfeld‐Kaas were studied in culture. Lack of nitrogen was the main trigger of encystment in both species. Irradiance had a secondary effect on the percentage of the population of each species that encysted. Temperature did not significantly affect encystment in either species. In both species, only a small percentage of the population underwent encystment. Low light had an inhibitory effect on the growth ofP. willeigrowing in nitrogen‐sufficient medium.