Temporal variability in lake phytoplankton is controlled by a complex between
hydrological and chemical factors, and biological interactions. We explored annual
change of phytoplankton in Lake Daecheong, using phytoplankton analysis data from 1997
to 2002 (except 2000). The standing crop of phytoplankton was ranged from 3.5 x 10 to
1.5 x 10? cells mL-¹ and the highest mean value was at site 1. The class composition
ratios of phytoplankton standing crop were divided into three classes. From January to
March, diatoms showed a dominance (68.1-77.7%). From April to June, diatoms were mixed
with cryptomonad etc. or blue-green algae. From July to October, blue-green algae
showed a dominance (54.7-84.0%). In the case of green algae, the class composition
ratios were below 10%. But green algae appeared all the year round.