Daily change in wind-induced sediment resuspension and phosphorus forms in a shallow eutrophic lake

We recorded the daily changes in wind and forms of phosphorus (P), including total P (TP), dissolved inorganic P (DIP), and particulate inorganic P (PIP), in Lake Teganuma, Japan. On the Kanto Plain, where Lake Teganuma is located, wind speed increases in the daytime and decreases in the night-time. In the daytime, TP increased, which was related to suspended solids (SS) and wind velocity, indicating that TP and SS were supplied by sediment resuspension. An increase in PIP during the daytime was also observed. However, a decrease in the PIP : SS ratio coincided with increasing DIP, indicating that release from PIP may increase DIP during the daytime. The DIP supply in the daytime was due to increased pH, which is related to phytoplankton growth. The night-time decrease in DIP with an increase in the PIP : SS ratio and high PIP concentration indicate DIP sorption by suspended inorganic matter. The night-time pH decrease influenced the PIP increase, resulting in depleted DIP (0.004 mg l(-1)). Therefore, the complicated P cycle, combining resuspension with P kinetics, suggests that daytime resuspension increases PIP, releasing DIP from SS-sorbed P, thus increasing available DIP and increasing phytoplankton and pH. The increased pH further releases DIP into the surface water. The release of P from PIP greatly influences the increase in DIP. Thus, the timing of resuspension creates a very suitable environment for phytoplankton in the lake. In contrast, during the night-time, PIP is a sink of inorganic P.