Abstract
The roles of the microflagellate, Monas guttula, that is a grazer on algae, is important in aquatic food chain. In order to understand the interaction of vertical migration on the relationship between the grazer and Microcystis viridis as a food source, grazing characteristics of M. viridis by a microflagellate M. guttula was studied using a large scale microcosm with a depth of 4m. Although the growth of M. guttula was inhibited during light period, the flagellate could favorably graze on the viable cells of M. viridis under the dark condition and was found to move to the dense layer of M. viridis. Finally, M. guttula perfectly grazed and degraded the M. viridis for 3 days.
