Characteristic distribution and structure of pranktonic archaea in the Arctic Ocean

Recent molecular biological techniques indicate that there are huge carbons derived from planctonic bacteria under euphotic zone, and those microbial carbon sources are now recognized one of the drive forces of the world ocean carbon cycle. And by present discover of widely-distributed planctonic archaea in the ocean, we have to calculate the microbial carbon cycle with archaeal quantitative densities and their metabolisms. However, in the world, microbial quantitative data is lacking. And more, there is less data in the Arctic Ocean. Ongoing changing the Arctic Ocean, the grasp of a detailed carbon cycle is requested. Microbial and ecological data will give a useful knowledge to understand global warning influence for the Arctic region. In summer 2008, the Arctic Ocean cruise by R/V MIRAI (MR08-04) was done in the Chukchi Sea, Canada Basin and Siberia Sea. In this cruise, we collected water samples using CTD at 20 stations to investigate the distributions of bacterial population density in the water column and compare the differences of bacterial population composition by sea area. We used Catalyzed Reporter Deposition Fluorescence in situ hybridization (CARD-FISH) technique targeting archaeal and eubacterial rRNA for identifying and enumerating marine microbial cells. In the Arctic Ocean, it was determined that the fraction of archaea increased with depth as with other oceans, and the vertical distribution of planctonic archaeal density was obviously different by sea area. Moreover, in East Siberian Sea, the fraction of crenarchaeota, one kind of the archaea, increased with depth and reached about 40% of total cells near the bottom. We expect that this high proportion would be come from obvious water mass structure and there environmental factors such as ammonium and nitrite concentrations. And it was considered that distribution and structure of pranktonic bacterial communities reflect the water mass structure in the Arctic Ocean.