Abstract
In order to clarify the movement of nitrogen (N) and phosphorus (P) between the sediment and overlying water in the eutrophic Lake Koyama in Tottori, the change in the cocentration of the different forms of N and P was investigated in 1993 and 1994.
The total N (T-N) concentration in the overlying water was fairly lower than that of the porewater. The ammonium-N (NH4-N) produced in the sediment was immediately diffused and/or was changed into organic N (Org.-N). The mineralization of N in the sediment was not controlled by the concentration of T-N or Org.-N of the sediment, but by the water temperature. The organic matter derived from the dead body of planktons seemed to be the main N supply to the sediment.
The concentration of T-P in the porewater was far lower than that of the overlying water and the P in the sediment existed in the form of Inorg.- P, which suggested that the elution of P from the sediment into the water was not probable, except for the period of the low dissolved oxygen concentration of the water in summer.
