Distribution of microbial methanogenesis, methane oxidation, and sulfate reduction in a high-temperature subduction system of the Nankai Trough off Cape Muroto (IODP Expedition 370 T-Limit, Site C0023)

Online Access: Get full text
Author(s): Treude, T.; Kallmeyer, J.; Beulig, Felix; Glombitza, Clemens; Schubert, F.; Krause, S.; Heuer, V. B.; Inagaki, F.; Morono, Y.
Author Affiliation(s): Primary:
University of California Los Angeles, Department of Earth, Planetary and Space Sciences, Los Angeles, CA, United States
GFZ Potsdam, Germany
Aarhus University, Denmark
NASA, Ames Research Center, United States
Bremen University, Germany
Japan Agency for Marine-Earth Science and Technology, Japan
Volume Title: AGU 2017 fall meeting
Source: American Geophysical Union Fall Meeting, Vol.2017; American Geophysical Union 2017 fall meeting, New Orleans, LA, Dec. 11-15, 2017. Publisher: American Geophysical Union, Washington, DC, United States
Note: In English
Summary: The aim of the IODP Expedition 370 is to explore the temperature limit of the deep biosphere in a sub-seafloor environment located in the Nankai Trough, where in-situ sediment temperature increases from 2°C at the seafloor to about 120°C at the 1.2 km deep sediment/basement interface. Our study focuses on the exploration of potential microbial methanogenesis, anaerobic oxidation of methane (AOM), and sulfate reduction in sediments from different depths (from ca. 200 to 1170 mbsf) exposed to several temperature settings in the laboratory (40, 60, 75/80 and 95°C). The drill site, which features a décollement between ca. 758-796 mbsf, includes a sulfate-poor methanogenic zone from approx. 400 to 600 mbsf, followed by a deep methane-sulfate transition zone between approx. 600 to 800 m, which transitions into a deep sulfate-rich zone. Potential microbial activity of hydrogenotrophic methanogenesis, AOM, and sulfate reduction was determined in incubations of sediment slurries produced from whole-round cores with H2-added artificial seawater medium using radioisotope techniques (14C-bicarbonate, 14C-methane, and 35S-sulfate, respectively). Preliminary results revealed two peaks of methanogenesis activity with rates in the order of 0.2 to 0.5 pmol g-1 dw d-1. One peak was located within the methane-rich zone passing into the methane-sulfate transition zone (60 to 80°C incubations), while the second peak occurred close to the basement (below 1000 mbsf, 95°C incubation). Sulfate reduction activity was generally highest above 400 mbsf (≈1000 pmol cm-3 d-1, 40°C incubation). Below 400 mbsf, rates declined to levels between 0.1 and 10 pmol cm-3 d-1 (60-95 °C incubations) without a clear trend and continued until close to the bottom of the core. The results point to potentially thermophilic and hypothermophilic microorganisms that exist under very low energy conditions. Samples from AOM incubations are currently being processed and preliminary results will be presented at the meeting as well as the results for sulfate reduction incubations with methane and acetate amendments.
Year of Publication: 2017
Research Program: IODP Integrated Ocean Drilling Program
IODP2 International Ocean Discovery Program
Key Words: 07 Marine Geology and Oceanography; Aliphatic hydrocarbons; Alkanes; Expedition 370; Hydrocarbons; IODP Site C0023; International Ocean Discovery Program; Methane; Nankai Trough; North Pacific; Northwest Pacific; Organic compounds; Oxidation; Pacific Ocean; Subduction zones; West Pacific
Coordinates: N322200 N322200 E1345759 E1345759
Record ID: 2019008531
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data supplied by, and/or abstract, Copyright, American Geophysical Union, Washington, DC, United States