Effects of Nutrient Concentration and Light Exposure on the Buoyancy of Subcultured Strain Microcystis aeruginosa

Abstract

Effects of nutrient (nitrogen and phosphorus) concentrations and light exposure on the buoyancy of subcultured Microcystis aeruginosa strain (UTEX LB 2061) were experimentally investigated, and the cellular content of polysaccharide (ballast) was measured to examine its relation to the buoyancy. The results showed that although vertical migration of subcultured M. aeruginosa was found out, its buoyancy seemed weak compared to that of wild Microcystis strain as often observed in lakes. The buoyancy of subcultured M. aeruginosa was affected by nutrient concentration rather than light exposure, and limitation of nitrogen or phosphorus resulted in cell settling. By contrast, the cellular content of polysaccharide depended on not nutrient concentration but light exposure. Consequently, the buoyancy of subcultured M. aeruginosa would be mainly regulated by gas vesicle volume but not ballast.