Abstract
In order to clarify the oceans role in the overall geochemical cycle of CO_2, getting to know a vertical concentration of phytoplankton is very important. The authors measured the vertical distribution of chlorophyll a in the western pacific equatorial ocean during the R/V MIRAI cruse (MR01-K05, MR02-K06), and analyzed a number of data which measured on the ship. The results show that the phytoplankton distribution has strong correlation with mixed layer depth and compensation depth. Using the CTD and ADCP data, the estimated model for the change of chlorophyll distribution is constructed.