Exploration of serpentine seamount, South Chamorro seamount
Abstract
Serpentinization and the following Fisher-Tropsch-type synthesis produce hydrogen and hydrocarbons. They become electron donors for microbes, and therefore it is believed that there are deep subseafloor microbial ecosystems supported by serpentinization. We have sought and elucidate the microbial ecosystem. South Chamorro Seamount is the one of the deep-sea serpentine mud volcanoes located in Mariana forearc (Fryer et al., 2006). These seamounts are formed by subducting Pacific plate under Mariana plate (Wheat et al., 2010). In this subduction process, the mantle in the Mariana plate on the fault was serpenrinized and the produced crustal fluid and muds were upwelling to the seafloor. South Chamorro Seamount has a big advantage to seek microbial ecosystems supported by serpentinization because there is borehole 1200c conducted by ODP#195 in 2001. Therefore we can access the deep subseafloor through the CORK observatory deployed on borehole 1200c. From the top of the CORK, the crustal fluid whose pH shows 12.3 was discharged. And also on the top of the CORK, brucites which was formed by mixing with seawater were also observed. Our first attempt is detection of microbes from this discharged crustal fluid. The number of cells is only 440 to 660 cells/mL, which indicated that two orders lower than that in seawater. But the analysis of microbial community structure showed that the major dominants are aerobic methanotrophs suggesting that discharged fluids were contamination with seawater. Therefore we have to sample directly from the depths of the borehole. To overcome this difficulty, we have developed a downhole sampling tool, Kandata system. This system is operated by only ROV and enables to directly sample crustal fluid and microbes and seal up them in the borehole. Therefore we can obtain deep crustal water and microbes without seawater contamination. In this February cruise we rolled down water sampler to 170 m below seafloor and sample water at this depth. And also to capture microbes we have set the in situ colonization system (ISCS) at same position for 6 months. We will recover this ISCS in this September cruise. In this conference, I will present these results of explorations in South Chamorro Seamount and discuss the deep subsurface microbial ecosystem driven by serpentinization.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2012
- Bibcode:
- 2012AGUFM.B43G0505M
- Keywords:
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- 0448 BIOGEOSCIENCES / Geomicrobiology;
- 3060 MARINE GEOLOGY AND GEOPHYSICS / Subduction zone processes;
- 4840 OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL / Microbiology and microbial ecology;
- 4894 OCEANOGRAPHY: BIOLOGICAL AND CHEMICAL / Instruments;
- sensors;
- and techniques