The first Arctic cruise of ARAON was conducted in the Chukchi Sea and Canada Basin from mid July to mid August in 2010. During the period, the carbon and nitrogen production rates of phytoplankton were measured at six different light depths of 19 stations in the Chukchi Sea and Canada Basin, using a 13C-15N dual isotope tracer. In addition, we identified the effect of light enrichments on the carbon and nitrogen production rates of phytoplankton in the chlorophyll a maximum layer. The averaged hourly carbon and nitrogen production rates vertically integrated from 100% to 1% light depth were 1.27 mg C m-2 h-1 (S.D.= ± 1.13 mg C m-3 h-1) and 4.20 mg N m-3 h-1 (S.D.= ± 4.58 mg N m-3 h-1) from this cruise. The nitrogen production rate of phytoplankton was somewhat higher than the carbon production rate. The small phytoplankton (0.7~5 µm) were dominated with value of over 50% in the study area. The light enrichment induced higher carbon and nitrogen production rates of the phytoplankton in the chlorophyll a maximum layer. The productivity increasing under higher light levels indicates that the growth of phytoplankton in this layer was light-limited during the cruise period in 2010. Primary production measurement by phytoplankton using a 13C-15N dual isotope tracer