Contribution of Vertical Methane Flux to Shallow Sediment Carbon Pools across Porangahau Ridge, New Zealand
Moderate elevated vertical methane (CH4) flux is associated with sediment accretion and raised fluid expulsion at the Hikurangi subduction margin, located along the northeast coast of New Zealand. This focused CH4 flux contributes to the cycling of inorganic and organic carbon in solid phase sedimen...
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MDPI AG
2014-08-01
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| Series: | Energies |
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| Online Access: | http://www.mdpi.com/1996-1073/7/8/5332 |
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| author | Richard B. Coffin Leila J. Hamdan Joseph P. Smith Paula S. Rose Rebecca E. Plummer Brandon Yoza Ingo Pecher Michael T. Montgomery |
| author_facet | Richard B. Coffin Leila J. Hamdan Joseph P. Smith Paula S. Rose Rebecca E. Plummer Brandon Yoza Ingo Pecher Michael T. Montgomery |
| author_sort | Richard B. Coffin |
| collection | DOAJ |
| description | Moderate elevated vertical methane (CH4) flux is associated with sediment accretion and raised fluid expulsion at the Hikurangi subduction margin, located along the northeast coast of New Zealand. This focused CH4 flux contributes to the cycling of inorganic and organic carbon in solid phase sediment and pore water. Along a 7 km offshore transect across the Porangahau Ridge, vertical CH4 flux rates range from 11.4 mmol·m−2·a−1 off the ridge to 82.6 mmol·m−2·a−1 at the ridge base. Stable carbon isotope ratios (δ13C) in pore water and sediment were variable across the ridge suggesting close proximity of heterogeneous carbon sources. Methane stable carbon isotope ratios ranging from −107.9‰ to −60.5‰ and a C1:C2 of 3000 indicate a microbial, or biogenic, source. Near ridge, average δ13C for pore water and sediment inorganic carbon were 13C-depleted (−28.7‰ and −7.9‰, respectively) relative to all core subsamples (−19.9‰ and −2.4‰, respectively) suggesting localized anaerobic CH4 oxidation and precipitation of authigenic carbonates. Through the transect there was low contribution from anaerobic oxidation of CH4 to organic carbon pools; for all cores δ13C values of pore water dissolved organic carbon and sediment organic carbon averaged −24.4‰ and −22.1‰, respectively. Anaerobic oxidation of CH4 contributed to pore water and sediment organic carbon near the ridge as evidenced by carbon isotope values as low as to −42.8‰ and −24.7‰, respectively. Carbon concentration and isotope analyses distinguished contributions from CH4 and phytodetrital carbon sources across the ridge and show a low methane contribution to organic carbon. |
| first_indexed | 2024-04-14T03:21:22Z |
| format | Article |
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| institution | Directory Open Access Journal |
| issn | 1996-1073 |
| language | English |
| last_indexed | 2024-04-14T03:21:22Z |
| publishDate | 2014-08-01 |
| publisher | MDPI AG |
| record_format | Article |
| series | Energies |
| spelling | doaj.art-fcc5a7465e074ed48b8c239dee7864682022-12-22T02:15:18ZengMDPI AGEnergies1996-10732014-08-01785332535610.3390/en7085332en7085332Contribution of Vertical Methane Flux to Shallow Sediment Carbon Pools across Porangahau Ridge, New ZealandRichard B. Coffin0Leila J. Hamdan1Joseph P. Smith2Paula S. Rose3Rebecca E. Plummer4Brandon Yoza5Ingo Pecher6Michael T. Montgomery7Naval Research Laboratory, Washington, DC 20375, USADepartment of Environmental Science and Policy, George Mason University, Fairfax, VA 22030, USAUnited States Naval Academy, Annapolis, MD 21402, USANaval Research Laboratory, National Research Council, Washington, DC 20375, USADepartment of Geology, University of Maryland College Park, College Park, MD 20742, USAHawaii Natural Energy Institute, University of Hawaii, Honolulu, HI 96822, USASchool of Environment, University of Auckland, Auckland 1142, New ZealandNaval Research Laboratory, Washington, DC 20375, USAModerate elevated vertical methane (CH4) flux is associated with sediment accretion and raised fluid expulsion at the Hikurangi subduction margin, located along the northeast coast of New Zealand. This focused CH4 flux contributes to the cycling of inorganic and organic carbon in solid phase sediment and pore water. Along a 7 km offshore transect across the Porangahau Ridge, vertical CH4 flux rates range from 11.4 mmol·m−2·a−1 off the ridge to 82.6 mmol·m−2·a−1 at the ridge base. Stable carbon isotope ratios (δ13C) in pore water and sediment were variable across the ridge suggesting close proximity of heterogeneous carbon sources. Methane stable carbon isotope ratios ranging from −107.9‰ to −60.5‰ and a C1:C2 of 3000 indicate a microbial, or biogenic, source. Near ridge, average δ13C for pore water and sediment inorganic carbon were 13C-depleted (−28.7‰ and −7.9‰, respectively) relative to all core subsamples (−19.9‰ and −2.4‰, respectively) suggesting localized anaerobic CH4 oxidation and precipitation of authigenic carbonates. Through the transect there was low contribution from anaerobic oxidation of CH4 to organic carbon pools; for all cores δ13C values of pore water dissolved organic carbon and sediment organic carbon averaged −24.4‰ and −22.1‰, respectively. Anaerobic oxidation of CH4 contributed to pore water and sediment organic carbon near the ridge as evidenced by carbon isotope values as low as to −42.8‰ and −24.7‰, respectively. Carbon concentration and isotope analyses distinguished contributions from CH4 and phytodetrital carbon sources across the ridge and show a low methane contribution to organic carbon.http://www.mdpi.com/1996-1073/7/8/5332coastal sedimentcarbon cyclingmethanephytodetritusconvergence forcingstable isotopes |
| spellingShingle | Richard B. Coffin Leila J. Hamdan Joseph P. Smith Paula S. Rose Rebecca E. Plummer Brandon Yoza Ingo Pecher Michael T. Montgomery Contribution of Vertical Methane Flux to Shallow Sediment Carbon Pools across Porangahau Ridge, New Zealand Energies coastal sediment carbon cycling methane phytodetritus convergence forcing stable isotopes |
| title | Contribution of Vertical Methane Flux to Shallow Sediment Carbon Pools across Porangahau Ridge, New Zealand |
| title_full | Contribution of Vertical Methane Flux to Shallow Sediment Carbon Pools across Porangahau Ridge, New Zealand |
| title_fullStr | Contribution of Vertical Methane Flux to Shallow Sediment Carbon Pools across Porangahau Ridge, New Zealand |
| title_full_unstemmed | Contribution of Vertical Methane Flux to Shallow Sediment Carbon Pools across Porangahau Ridge, New Zealand |
| title_short | Contribution of Vertical Methane Flux to Shallow Sediment Carbon Pools across Porangahau Ridge, New Zealand |
| title_sort | contribution of vertical methane flux to shallow sediment carbon pools across porangahau ridge new zealand |
| topic | coastal sediment carbon cycling methane phytodetritus convergence forcing stable isotopes |
| url | http://www.mdpi.com/1996-1073/7/8/5332 |
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