Abstract
Kinetic studies on the growth of Microcystis aeruginosa, Chlamydomonas sp. and Synedra acus were carried out on 2 member cultures in a microcosm system (diameter=1.0m, depth=3.0m) as well as small scale unialgal cultures to study the process of water-bloom formation by M. aeruginosa. In the microcosm cultures, aeration from the bottom was conducted to assess the effect of aeration/circulation on the water-bloom. The specific growth rate of M. aeruginosa was larger than that of Chlamydomonas under low light intensity (less than 1, 000 lux), whereas that of Chlamydomonas was larger under high light intensity at 20°C and 30°C. Thus Microcystis seemed to predominate over Chlamydomonas and subsequently form the water-bloom when light intensity underwater decreased sharply with depth of water due to light shielding by high concentration of suspended solids and/or phytoplankton. The specific growth rate of M. aeruginosa in 30°C was greater than that of S. acus, and therefore, predominated over S. acus.
Aeration and mixing of the whole water column in the microcosm delayed or prevented the dominance of M. aeruginosa. The artificial mixing and/or aeration seemed to be an effective way to control water-bloom formation by M. aeruginosa.
