Temporal and spatial distributions of Microcystis aeruginosa in the light-shaded artificial enclosure

In order to investigate the temporal and spatial distributions of Microcystis aeruginosa in light-shaded condition, a 1.4 m deep enclosure in artificial lake was introduced. After Microcystis aeruginosa bloom was induced in artificial enclosure in October of 2006, the light shading material was covered on the surface and the variation of chlorophyll a content, pH and DO were analyzed in next 10 days. After 7 days of light shading, Chlorophyll a, DO and pH declined from 107.1 μg/L, 9.7 mg/L and 9.1 to 44.5 μg/L, 2.6 mg/L and 8.0 respectively. Meanwhile, microcystis colony's radius decreased obviously, from 71.4% larger than 50um to almost less than 50um. Light shading could effectively control the bloom of harmful algae. By means of monitoring chlorophyll a content at different water depths, microcystis colonies floated upward to the water surface within 5 days in light shading. The buoyancy control mechanism of Microcystis aeruginosa might explain this phenomenon.