No difference in colony formation of Scenedesmus obliquus exposed to lakes with different nutrient levels

The algal genus Scenedesmus is famous for its highly phenotypic plasticity in response to various environmental factors. In laboratory, axenic cultures of Scenedesmus often fail to form colonies and remain in unicellular morph. To examine whether unicellular Scenedesmus can form colonies after exposure to natural lakes, dialysis bags and plastic bottles which contained the precultured Scenedesmus obliquus were exposed in two lakes with different nutrient levels for four weeks. Results showed S. obliquus grew well in dialysis bags but not in plastic bottles; S. obliquus can form colonies when incubated in dialysis bags which allow exchange with the aquatic environment of the substances, regardless of the nutrient levels of the two lakes. However, no colonies were observed in S. obliquus incubated in plastic bottles exposed in both lakes. This suggested that active growth and zooplankton infochemicals contributed together to the colony formation of S. obliquus exposed in situ environment.