Abstract: Submersed macrophyte, as a priliminary producer of lake ecosystems, have important environmental functions in fixing bottom sediment, preventing sediment resuspension, and purifying water quality. Probing into the distribution, community structure and succession law of submersed macrophyte in lake is of vital importance in protecting and restoring lake water eco-environment. Traditional investigation methods are inefficient, and will also cause damages to the submersed macrophytes. In view of this, by employing dual-frequency identification sonar (DIDSON) which could obtain clear image in turbid and dark water, we acquired the underwater images of four typical submersed macrophytes in Gonghu bay of Taihu Lake in different seasons on the premise of not disturbing submersed macrophytes. Furthermore, we extracted the coverage of submersed macrophytes through post-processing. Results manifested that the coverages of submersed macrophytes in Lake Taihu acquired by DIDSON were close to the results by traditional methods, and DIDSON is more convenient and efficient. The research results provide support for lake water eco-environment restoration.

Key words: submersed macrophyte, coverage, DIDSON, image processing, artificial plot method, lake water ecology