The Joint Ocean Ice Study (JOIS) was conducted in the Canada Basin from mid September to mid October in 2009. During the period, the primary productivity of phytoplankton was measured at six different light depths of 11 stations in the Canada Basin, using a 13C-15N dual isotope tracer. In addition, we identified the effects of light and nutrient enrichments on the primary production of phytoplankton in the chlorophyll a maximum layer. The temperature and salinity at surface were -2~ 1℃ and 24-27, respectively in the Canada Basin. In contrast, the very salty water (>31) was existed below 60 m water depth and the strong stratification was developed at the depth. In general, the NO3- concentration was depleted from surface to 60 m over the North of 72°. The primary productivity of phytoplankton was somewhat lower in the Canada Basin during the cruise period in 2009 compared to other regions in the Arctic Ocean. The averaged hourly primary production rate vertically integrated from 100% to 1% light depth was 1 mg C m-2 h-1 from this cruise. The production rates were not significant different depending on different sea ice concentrations (50%). The light and nutrient enrichments induced higher primary productivity of the phytoplankton in the chlorophyll a maximum layer. The increases of primary productivity at the stations with 50% ice cover. This is probably because the phytoplankton at the stations with the higher ice cover was more shade-adapted and thus slower response on the light enrichments. 1) Quantification of Primary production of phytoplankton and Physical • Chemical environmental conditions in the Canada Basin 2) The effect of light and nutrient on the primary production of phytoplankton in the Chl a maximum layer