Abstract
The organisms in the rock bed contact-purification channel were investigated in the experimental plant (30m long × 1m wide × 1.3m deep × 6 channels) operated at the innermost part of Tokyo Bay to understand the biological aspects in the channels for improvement of the eutrophic coastal water. The dominant species of phytoplankton in the influent were diatoms such as Skeletonema costatum, Navicula and Nitzschia often observed in the coastal water. As for microanimals in the biofilms on the rocks, Carchesium, Vorticella and Zoothamnium became the dominant species sequentially. S. costatum and Navicula were present in all seasons as the dominant species of microplants in the biofilms. Other than the above microorganisms, 17 species of large size sessile and benthic animals were observed in the biofilms, in the rock beds and on the channel walls after 9 months of operation. Those sessile or benthic animals gradually decrease the porosity of the rock bed with its individual growth and their growth in numbers and finally may cause clogging of the channel, while they contribute to water purification and sediment reduction. The result of the observation indicates that the fauna (sessile and benthic animals) observed in the rock bed channel are similar to those of nearby water areas, especially those of the quaywall of No.13 Marine Terminal and the artificial beach of Kasai Seaside Park located in the innermost part of the Tokyo Bay in this study.
