2019 Volume 32 Issue 5 Pages 245-254
Environmental factors affect microbial community in shallow groundwater. However, the microbial dynamics in deep groundwater have not been investigated enough. This study aims to elucidate the abundance and constituents of the microbial communities in the groundwater deeper than 700 m, at the coastal area of Hokkaido, Japan. Characteristics of the microbial distribution were discussed considering the hydrologic parameters such as dissolved inorganic materials. The density of prokaryotes shows 2.68 (±0.03) × 103 cells/mL and the relative ratio of Bacteria to the total abundance of prokaryotes shows 14.9 % at the depth of 715 m, whereas the density of prokaryotes shows 1.87 (±0.03) × 105 cells/mL and the relative ratio of Bacteria shows 48.8 % at the depth of 943 m in the groundwater. The main genus detected by the next-generation sequence shows absolute anaerobic, thermophilic, halophilic and alkalophilic bacteria as the major community constituents at the depth of 943 m. This suggests that the groundwater would have been affected by the seawater. Also, the methane is observed in the groundwater due to the microbial activity. Therefore, the information of the microbial dynamics seems to be important to understand the subsurface environment especially focusing on the groundwater.
