Abstract
Plankton communities and physicochemical factors were investigated to determine annual changes in the picoplankton communities for one year in the eutrophic subtropical Senbaru Pond in Okinawa-jima, Japan. Cyanobacteria dominated in the picoplankton communities throughout the whole year. The cell densities of picoplankton was high (7.52×103-1.03×107 cells·mL-1). The densities showed positive correlations with water temperatures. In particular, the densities increased over 25 degrees. Nutrients were not limiting factors for growth of picoplankton in Senbaru Pond. The values of turbidity were high after the heavy rains because of red soil runoff; however, there were no correlations between the cell densities and the turbidities. It was considered that water temperature rather than nutrients strongly affected the cell density in Senbaru Pond.
