IODP Proceedings    Volume contents     Search


Data report: water activity of the deep coal-bearing basin off Shimokita from IODP Expedition 3371

Wataru Tanikawa,2, 3 Yoko Ohtomo,4 Glen Snyder,5 Yuki Morono,2, 3 Yu’suke Kubo,6 Yoshihiro Iijima,7 Takuroh Noguchi,8 Kai-Uwe Hinrichs,9 and Fumio Inagaki2, 3, 10


Water activity (Aw) is one of the physicochemical properties that may influence microbial activity in deep subseafloor environments; however, Aw for subseafloor sediments has never been examined, even at shallow depths. This study investigated Aw data obtained from core samples collected during Integrated Ocean Drilling Program Expedition 337 in the deep-water coal-bearing basin off Shimokita, Japan. Aw did not show any depth dependence and was relatively low in coal-bearing layers. Aw at depths of 0–2466 meters below seafloor ranged from 0.95 to 0.98, which is quite high and well suited to sustaining microorganisms. Aw for sedimentary rocks was less affected by lithology and porosity than it was by the NaCl concentration and degree of fluid saturation. In addition, the Aw measurements performed in this study yielded results that corresponded closely with values estimated using Raoult’s law and interstitial water chemistry. It therefore appears that Aw for deep-marine sediments is strongly affected by pore water chemistry. The low Aw anomaly in the coalbed unit is considered to be due to contamination by drilling mud and fluid into core samples.

1 Tanikawa, W., Ohtomo, Y., Snyder, G., Morono, Y., Kubo, Y., Iijima, Y., Noguchi, T., Hinrichs, K.-U., and Inagaki, F., 2018. Data report: water activity of the deep coal-bearing basin off Shimokita from IODP Expedition 337. In Inagaki, F., Hinrichs, K.-U., Kubo, Y., and the Expedition 337 Scientists, Proceedings of the Integrated Ocean Drilling Program, 337: Tokyo (Integrated Ocean Drilling Program Management International, Inc.). doi:10.2204/iodp.proc.337.204.2018

2 Kochi Institute for Core Sample Research, JAMSTEC, Japan. Correspondence author:

3 Research and Development Center for Submarine Resources, JAMSTEC, Japan.

4 Faculty of Engineering, Hokkaido University, Japan.

5 Gas Hydrate Research Laboratory, Meiji University, Japan.

6 Center for Deep Earth Exploration, JAMSTEC, Japan.

7 Graduate School of Bioresources, Mie University, Japan.

8 Interdisciplinary Science Unit, Research and Education Faculty, Kochi University, Japan.

9 Center for Marine Environmental Sciences, University of Bremen, Germany.

10 Research and Development Center for Ocean Drilling Science, JAMSTEC, Japan.

Initial receipt: 11 April 2017
13 November 2017
Publication: 22 March 2018
MS 337-204