抄録
Colony size is an important factor in developing algal blooms. For the purpose of determining the relationship between colony size and cell density for growth strategy, the growth monitoring of bloom-forming cyanobacteria was monitered the Kitayamada Fishery Harbor in the southern basin of Lake Biwa from July to September 1999, with colony size measured using an image analysis system. The cell densities of Microcystis aeruginosa and Microcystis wesenbergii (Cyanobacteria) increased gradually during this period and surface-water blooms developed at the end of August and at the end of September, separated by a period of no growth in early September. However seasonal changes in mean colony size did not occur in concordance with seasonal changes in cell density. The percentage of large colonies (>300μm) increased in early September, when the mean diameters of the colonies of both species reached their after peaks. These results suggest than Microcystis colony size is likely to be the largest during a quiescent stage of their life cycle after a period of increased cell density.
