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Methane hydrate-bearing seeps as a source of aged dissolved organic carbon to the oceans

January 1, 2011

Marine sediments contain about 500-10,000 Gt of methane carbon, primarily in gas hydrate. This reservoir is comparable in size to the amount of organic carbon in land biota, terrestrial soils, the atmosphere and sea water combined, but it releases relatively little methane to the ocean and atmosphere. Sedimentary microbes convert most of the dissolved methane to carbon dioxide. Here we show that a significant additional product associated with microbial methane consumption is methane-derived dissolved organic carbon. We use ??14 C and ??13 C measurements and isotopic mass-balance calculations to evaluate the contribution of methane-derived carbon to seawater dissolved organic carbon overlying gas hydrate-bearing seeps in the northeastern Pacific Ocean. We show that carbon derived from fossil methane accounts for up to 28% of the dissolved organic carbon. This methane-derived material is much older, and more depleted in 13 C, than background dissolved organic carbon. We suggest that fossil methane-derived carbon may contribute significantly to the estimated 4,000-6,000 year age of dissolved organic carbon in the deep ocean, and provide reduced organic matter and energy to deep-ocean microbial communities. ?? 2011 Macmillan Publishers Limited. All rights reserved.

Citation Information

Publication Year 2011
Title Methane hydrate-bearing seeps as a source of aged dissolved organic carbon to the oceans
DOI 10.1038/ngeo1016
Authors J.W. Pohlman, J.E. Bauer, W.F. Waite, C.L. Osburn, N.R. Chapman
Publication Type Article
Publication Subtype Journal Article
Series Title Nature Geoscience
Series Number
Index ID 70034044
Record Source USGS Publications Warehouse
USGS Organization