Restoration Attempt of Submerged Macrophytes in an Eutrophic Shallow Lake in Japan

We have tried to develop a procedure to rehabilitate submerged macrophytes in lakes and marshes where they had been disappeared. Diaspore of submerged macrophytes from bottom sediments should be retrieved and used to restore locally native species. We investigated the distribution of the density of diaspore in lake bottom sediments and the germination potential of diaspore in Lake Kasumigaura, Japan. We have shown that the densely distributed diaspore was found in the vicinity of the river mouths and bays. Germination tests for sediment samples taken from several depths showed that the density of diaspore was high at the depth of 20–50cm from sediment surface, and the number of germination of submerged macrophytes was high at the depth of 10–40cm from sediment surface. Age determination of the bottom sediment showed that these sediment layers were deposited during periods when submerged plants were dominant in the lake. This result implies the possibility of the rehabilitation of native submerged macrophytes from diaspore in bottom sediments in Lake Kasumigaura.