Author(s)

K. Shimada, N. Kitamura, Y. Yoshida, H. Matsushima & Y. Asada

Abstract

Because of the toxic microcystin from Microcystis aeruginosa (M.a.) in eutrophicated lakes and reservoirs, effective counter measures against its excessive growth have been widely called for. Recent research on the growth control of Microcystis was conducted especially concerning the effects of straw and emergent plants. The authors have discussed that the water soluble extract (WSE) from the dead leaves of deciduous trees like cherry (Purunus Yedoensis）and maple (Acer buergerianum Miq.) bring about a clear effect on the growth control of M.a. The WSE solutions from the dead leaves of cherry and maple trees were added to an M.a. culture solution to set the initial condensed tannin loading intensity (CTLI) per unit cell at about 26 pg-CT/cell, and then, the daily change of the M.a. cell concentration was observed. Accordingly, the WSE addition resulted in controlling the cell concentration and its influence was clearly affected by the initial CTLI level. The condensed tannin (CT) in the WSE solution was preferentially separated to produce a CT fraction (CTF) solution by use of casein/acetone, and thus the CTF solution also caused a good growth control. The WSE fractioning treatment resulted in separating the CT substance from the WSE solution. As for the growth control tests using the

Keywords

water soluble extract, condensed tannin, dead leaves, growth control, Microcystis aeruginosa