Field observations have been made with respect to the diel vertical migration of dinoflagellate, Peridinium bipes and nutrient concentration profiles in a thermal stratified reservoir. Results showed that P. bipes could take nutrients and photosynthesize by migration in a calm thermal stratified mesotrophic reservoir. Faster migration from surface layer to middle layer was advantageous to take nutrients, and the possibility of active migration of P. bipes was suggested from the estimation of setting velocity. Furthermore, observational results suggested that P. bipes migration played an important role in nutrient cycling in a stratified reservoir.
