The Distribution and Relative Abundance of Bloom Forming Microcystis Species in Several Eutrophic Waters

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The species variation and relative abundance of the blue-green alga, Microcystis, were studied with blooming water samples from various eutrophic lakes, reservoirs and ponds. Using the taxonomical system of KOMÁREK (1958), Microcystis aeruginosa f. aeruginosa (M-AA), M. aeruginosa f. flos-aquae (M-AF). M. wesenbergii (M-W) and M. viridis (M-V) were identified. The mode in relative abundance of each species was variable ; M-AA was the most dominant species in 67 %, M-W in 19 %, and M-V in 14 % of the water bodies examined, whereas M-AF was never present as the predominant form. A seasonal shift in the relative abundance was found in Himonya Pond (Tokyo), where M-AA was predominant in the early stage of bloom development, M-W increased in the later period and was present in a higher proportion in the overwintering population in the pond water. The presence of intra species variations and some problems concerning the species identification of the alga were discussed.