I. Introduction
For last few decades, algal bloom has been a serious problem, leading imbalance of organisms in the water. Severe algal bloom directly affects water quality as some of algae such as cyanobacteria produce toxic that are harmful to other species—including humans. Hence, the Korean Government has been operating the algal warning system since 1998 based on chlorophyll-a concentration and the number of cyanophyceae cells. Although using the concentration of chlorophyll-a as the primary indicator has been debatable, it is still widely used as it can be measured at low cost, whereas counting cyanophyceae cells incur considerable human labor.