THE ESTIMATION OF BACTERIA MAT AND METHANE PLUME FORMATION TREND BY COMMUNITY STRUCTURE ANALYSIS OF METHANE RELATED ARCHAEA

In the eastern margin of Japan Sea, many bacteria mats and methane plumes are observed on seafloor in wide area, associated with shallow methane hydrate. The formation of bacteria mats in the methane rich area has relationship with methanotrophic archaea (ANMEs), and also reported that these mats has specific community structure of ANMEs. In order to know the forming mechanism of the bacteria mats and relationship between ANMEs and bacteria mats in Japan Sea, we conducted community structure analysis of methane related archaea by clone library method. Sediments were sampled from two types of bacteria mats and surrounding sediments. The two types are black mat and white mat. In many cases, those mats are found associating with methane plumes or fluid flow. As the result of the analysis, we found out that there are specific community structures in both type of mats. Black mat had same structure associated with ANME-2. On the other hand, white mat had two types of community structures. One associated with ANME-1 and other associated with methanogens. Therefore, we estimate that there are two types of origin of the bacteria mat or methane plume. One is originating from the deeper environment origin methane. Other is originating from the deeper environment or water column origin substrate, such as methanol, methylamine, etc.

This study was conducted under the commission from AIST as a part of the methane hydrate research project funded by METI (the Ministry of Economy, Trade and Industry, Japan).