Carbon dioxide and methane emissions from an artificially drained coastal wetland during a flood: Implications for wetland global warming potential. Issue 8 (28th August 2014)

• Record Type: Journal Article
• Authors: Gatland, J. R.; Santos, I. R.; Maher, D. T.; Duncan, T. M.; Erler, D. V.
• Is Part Of: Journal of geophysical research. Volume 119:Issue 8(2014)
• Page Start: 1698
• Page End: 1716
• Publication Date: 2014-08-28
• Subjects: Geobiology -- Periodicals; Biogeochemistry -- Periodicals; Biotic communities -- Periodicals; Geophysics -- Periodicals; 577.14
• DOI: 10.1002/2013JG002544
• Languages: English
• ISSNs: 2169-8953

Abstract

<abstract abstract-type="main"> <title>Abstract</title> <p>Floods frequently produce deoxygenation and acidification in waters of artificially drained coastal acid sulfate soil (CASS) wetlands. These conditions are ideal for carbon dioxide and methane production. We investigated CO<sub>2</sub> and CH<sub>4</sub> dynamics and quantified carbon loss within an artificially drained CASS wetland during and after a flood. We separated the system into wetland soils (inundated soil during flood and exposed soil during post flood period), drain water, and creek water and performed measurements of free CO<sub>2</sub> ([CO<sub>2</sub>*]), CH<sub>4</sub>, dissolved inorganic and organic carbon (DIC and DOC), stable carbon isotopes, and radon (<sup>222</sup>Rn: natural tracer for groundwater discharge) to determine aquatic carbon loss pathways. [CO<sub>2</sub>*] and CH<sub>4</sub> values in the creek reached 721 and 81 μM, respectively, 2 weeks following a flood during a severe deoxygenation phase (dissolved oxygen ~ 0% saturation). CO<sub>2</sub> and CH<sub>4</sub> emissions from the floodplain to the atmosphere were 17‐fold and 170‐fold higher during the flooded period compared to the post‐flood period, respectively. CO<sub>2</sub> emissions accounted for about 90% of total floodplain mass carbon losses during both the flooded and post‐flood periods. Assuming a 20 and 100 year global warming potential (GWP) for CH<sub>4</sub> of 105 and 27 CO<sub>2</sub>‐equivalents, CH<sub>4</sub> emission contributed to 85% and 60% of total floodplain CO<sub>2‐</sub>equivalent emissions, respectively. Stable carbon isotopes (<italic>δ</italic><sup>13</sup>C in dissolved CO<sub>2</sub> and CH<sub>4</sub>) and <sup>222</sup>Rn indicated that carbon dynamics within the creek were more likely driven by drainage of surface floodwaters from the CASS wetland rather than groundwater seepage. This study demonstrated that >90% of CO<sub>2</sub> and CH<sub>4</sub> emissions from the wetland system occurred during the flood period and that the inundated wetland was responsible for ~95% of CO<sub>2</sub>‐equivalent emissions over the floodplain.</p> </abstract>