Plankton is an important organism supporting aquatic ecosystem from its bottom on the trophic levels as a primary producer. In our laboratory, we research mainly about the relationship between population dynamics of phytoplankton and environmental conditions, and about the export of organic matter in the marine ecosystem, from the viewpoints of biological and chemical oceanography. Furthermore, to reveal the physiology and ecology of marine harmful microalgae, such as causative species of red tides killing fishes, and/or as toxic species causing toxification of bivalves (scallops and clams, etc.), we also have conducted related experiments and field survey.