Phytoplankton play an important role in the ocean carbon cycle. This ocean lidar technology determines the depth-wise distribution of phytoplankton. A strong pulsed laser light is released into the sea. This light stimulates the chlorophyll in the phytoplankton, causing them to fluoresce in red. The level of this fluorescence is measured by the lidar. At JAMSTEC, we are currently developing a shipboard ocean lidar observation system for the Mirai, which will allow us to determine the role of phytoplankton in the carbon cycle, as part of the Joint Global Ocean Flux Study (JGOFS).