In dam reservoirs, monitoring of phytoplankton and zooplankton is important for effective operation and management. The conventional method for plankton identification by microscopic examination, according to the National Census on River Environment in Japan, requires experienced technicians; however, the number of such technicians is decreasing. Moreover, many identification errors have been made between similar plankton owing to identification based on morphology. Here, we aimed to establish a simple and quick method to identify plankton, focusing on DNA sequences using a next generation sequencer. The results of investigations conducted in four dam reservoirs showed that a remarkably higher number of genera and species were identified using the next generation sequencer compared to the conventional method. Approximately 120-180 phytoplankton species were identified by the method based on DNA, while 10-20 species were detected by the microscopy method. In addition, 400?500 zooplankton species were identified by the method based on DNA, in contrast to only 20 to 50 species identified by the microscopy method. Furthermore, the method based on DNA has the potential to predict some problems in drinking water supply, as plankton and bacteria smaller than 2 ?m (which are difficult to identify using an optical microscope) can easily be identified. |