Environmental conditions and C and N uptakes of phytoplankton in the Bering and Chukchi seas, 2008

As a Chinese IPY event, the 3rd Chinese National Arctic Research Expedition (CHINARE) was conducted from the Chukchi Sea to the central Arctic Ocean from late July to early September in 2008. During the period, the primary productivity experiments were measured at 12 stations in the Chukchi Sea and 12 stations in the central Arctic Ocean, using a 13C-15N dual isotope tracer. In addition, we measured ice algae productivities in the melting ponds from 5 different ice stations. The temperature and salinity at surface were 4-6 ℃ and 30 in the Chukchi Sea and -1-3 ℃ and 25-27 in the central Arctic Ocean. The primary productivity of phytoplankton was higher in the Chukchi Sea than in Canada Basin during the cruise period. The nitrogen up take rates in the Chukchi Sea were lower in 2008 than in 2007. Based on high f-ratios in the central Arctic sea, nitrate uptake rates compared to ammonium uptake rates were relatively higher than those from other studies. The productivity of the algae in melting ponds ranged from 0.01 to 0.34 mg C m-3 h-1(average± S.D.= 0.09±0.11 mg C m-3 h-1) which were some what higher than those of phytoplankton(average± S.D.= 0.07±0.06 mg C m-3 h-1) at surface water over 80°N in the Arctic Ocean. From the careful examination on micro algae communities within or under sea ice at the refrozen surface of the melting ponds, they are believed to an important food source for the zooplanktons such as copepods and amphipods as well as Arctic cods before along winter period. However, current and on going climate changes such as a sea ice decrease are expected to impact largely on this unique habitat in the melting ponds.
1) Primary production measurement by phytoplankton using a 13C-15N dual isotope tracer
2) Developmental stages of melting ponds and ice algal productivity