Next Article in Journal
Active Power Filtering Using the ZDPC Method under Unbalanced and Distorted Grid Voltage Conditions
Next Article in Special Issue
Transport Mechanisms for CO2-CH4 Exchange and Safe CO2 Storage in Hydrate-Bearing Sandstone
Previous Article in Journal
Effect of Extended Extinction from Gold Nanopillar Arrays on the Absorbance Spectrum of a Bulk Heterojunction Organic Solar Cell
Previous Article in Special Issue
Experimental Investigation into the Combustion Characteristics of Propane Hydrates in Porous Media
Article Menu

Export Article

Open AccessArticle
Energies 2015, 8(3), 1561-1583;

Deep Sediment-Sourced Methane Contribution to Shallow Sediment Organic Carbon: Atwater Valley, Texas-Louisiana Shelf, Gulf of Mexico

Naval Research Laboratory, Washington, DC 20735, USA
Marine, Earth, and Atmospheric Sciences, North Carolina State University, Raleigh, NC 27695, USA
Department of Geology, University of Maryland, College Park, MD 20742, USA
Oceanography Department, US Naval Academy, Annapolis, MD 21402, USA
Current Address: Department of Physical and Environmental Sciences, Texas A&M University—Corpus Christi, Corpus Christi, TX 78412, USA
Author to whom correspondence should be addressed.
Academic Editor: Enrico Sciubba
Received: 23 August 2014 / Accepted: 11 February 2015 / Published: 18 February 2015
(This article belongs to the Special Issue Coastal Ocean Natural Gas Hydrate 2014)
Full-Text   |   PDF [2484 KB, uploaded 17 March 2015]   |  


Coastal methane hydrate deposits are globally abundant. There is a need to understand the deep sediment sourced methane energy contribution to shallow sediment carbon relative to terrestrial sources and phytoplankton. Shallow sediment and porewater samples were collected from Atwater Valley, Texas-Louisiana Shelf, Gulf of Mexico near a seafloor mound feature identified in geophysical surveys as an elevated bottom seismic reflection. Geochemical data revealed off-mound methane diffusion and active fluid advection on-mound. Gas composition (average methane/ethane ratio ~11,000) and isotope ratios of methane on the mound (average δ13CCH4(g) = −71.2‰; D14CCH4(g) = −961‰) indicate a deep sediment, microbial source. Depleted sediment organic carbon values on mound (δ13CSOC = −25.8‰; D14CSOC = −930‰) relative to off-mound (δ13CSOC = −22.5‰; D14CSOC = −629‰) suggest deep sourced ancient carbon is incorporated into shallow sediment organic matter. Porewater and sediment data indicate inorganic carbon fixed during anaerobic oxidation of methane is a dominant contributor to on-mound shallow sediment organic carbon cycling. A simple stable carbon isotope mass balance suggests carbon fixation of dissolved inorganic carbon (DIC) associated with anaerobic oxidation of hydrate-sourced CH4 contributes up to 85% of shallow sediment organic carbon. View Full-Text
Keywords: methane; advection; geochemistry; carbon isotopes; sediment carbon methane; advection; geochemistry; carbon isotopes; sediment carbon

Figure 1

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

Supplementary materials


Share & Cite This Article

MDPI and ACS Style

Coffin, R.B.; Osburn, C.L.; Plummer, R.E.; Smith, J.P.; Rose, P.S.; Grabowski, K.S. Deep Sediment-Sourced Methane Contribution to Shallow Sediment Organic Carbon: Atwater Valley, Texas-Louisiana Shelf, Gulf of Mexico. Energies 2015, 8, 1561-1583.

Show more citation formats Show less citations formats

Related Articles

Article Metrics

Article Access Statistics



[Return to top]
Energies EISSN 1996-1073 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top