Oshoro-Maru cruise in 2007 provided an important opportunity to compare the 4 areas with different environmental conditions from the southwestern Bering Sea to the Northern Chukchi Sea. Carbon/nitrogen uptake rates and nutrient measurements were obtained at 17 stations. In addition, 3 different UV light were measured at every 1hour at 4 stations. In the southern Bering Sea, there was a strong stratification at 20 m water depth, which is a characteristic water structure during the summer period. In the Chukchi Sea, there was a thermal stratification existed at 10 m depth after the Bering Strait. But, the salinity structure in the central Chukchi Sea showed some mixing from surface to bottom. In general, inorganic nutrients were not totally depleted in the euphotic layers, which might indicate the nutrients are not limiting to the phytoplankton production in the sampling areas for this time of 2007. Integrated chlorophyll-a in the water column were generally low (< 50 mg chl-a m-2) in the study areas, except C05 and C06 (> 500 mg chl-a m-2). The mean hourly carbon uptake rates were 13.0 ± 3.1 mg C m-2 h-1 and 10.2 ± 4.9 mg C m-2 h-1) respectively for the southern Bering Sea (B14, B21, B04, B10) and northern Bering Sea (B26, B40, B42). The mean rate in the central Chukchi Sea (RC03 and C04) was 108.3 mg C m-2 h-1. If the photic hour is 15 hours a day, then the daily carbon uptake rate was 1.63 g C m-2 d-1, which is comparable to the recent study although the chlorophyll-a concentration was so high (> 500 mg chl-a m-2) in this year. In comparison, the mean hourly nitrogen uptake rate was 45.2 mg N m-2 h-1 in the central Chukchi Sea which was higher than 22.6 mg N m-2 h-1 in Lee et al. (2007), but lower than 85.5 mg N m-2 h-1 in Hansell and Goering (1990). In the northern Bering Sea, the rate was 12.6 mg N m-2 h-1 which was rather higher than those from other study regions, but the ammonia uptake rate here except the station B26 was much higher than the nitrate uptake rate based on f-ratio (0.15). This is indicating that ammonium is an important nitrogen source in this region. In the central Chukchi Sea, the f-ratio was 0.68 which suggests nitrate was about 70 % of total nitrogen source for the phytoplankton production. 1) To investigate on water temperature and salinity distribution and major inorganic nutrients concentration in the study area 2) To study on primary productivity of phytoplankton and relationship with environmental factors in Bering and Chukchi Sea 3) To study on productivity of ammonia and nitrogen in Bering and Chukchi Sea