Studies on biological control of toxic boom-forming cyanobacteria.

2001 Fiscal Year Final Research Report Summary

• Project/Area Number: 11480155
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: 環境保全
• Research Institution: Rissho University
• Principal Investigator: WATANABE Mariyo F. Rissho University, Environment System, Associate Professor, 地球環境科学部, 助教授 (70301835)
• Co-Investigator(Kenkyū-buntansha): HAMABATA Etsuji Lake Biwa Research Institute, Principal Researcher, 専門研究員 (40238077) ; NAMIKOSHI Michio Tokyo University of Fisheries, Professor, 海洋環境学科, 教授 (30189196) ; NAKAJIMA Takuo Lake Biwa Research Institute, Associate Director, 総括研究員 (30237268) ; TSUJIMURA Shigeo Lake Biwa Research Institute, Researcher, 研究員 (60300969)
• Project Period (FY): 1999 – 2000
• Keywords: Water bloom / Water plant / Allelopathy / Bioactive substance

Research Abstract

(1) Establishment of assay method to detect growth inhibition to cyanobacteria : Microcystis aeruginosa was used as a typical bloom-forming cyanobacteria to detect growth inhibition of substances. The species was cultured in 48 well micro plate for one week. This assay method has an advantage to obtain at least three samples, which enable to apply the statistical significant test. The reduction of chlorophyll a peak was also applied to detect the growth inhibition activity in more short time during the course of fractionation of the extracts of algae and water plants.
(2) Detection of substances having growth inhibition activity : The growth inhibition activity was tested in the water extracts and the culture media of cyanobacteria with trichome and water plants. The activity was detected in the water extract of a cyanobacterial cells, and the water extracts and the culture media of six species of water plants.
(3) Identification of substances having growth inhibition activity : Unsaturated fatty acids were identified as growth inhibiting substances from the methanol extract of a cyanobacteria. The identification of substances contained in water plants is progressing, especially for the substances which water plants excrete to water bodies.
(4) Growth test of a water plant in a pond, Mishimaike : Two enclosures were set up in a pond in Shiga Prefecture. Elodea nuttallii was planted in one enclosure and the water quality was compared with that contained no water plant. The reduction of growth of phytoplankton was observed in the enclosure with the water plant. It was also shown that a water plant played an important rule as nutrient absorbing body.