Methane emissions along a salt marsh salinity gradient |
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Authors: | Karen B. Bartlett David S. Bartlett Robert C. Harriss Daniel I. Sebacher |
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Affiliation: | (1) Department of Biology, The College of William and Mary, 23185 Williamsburg, VA;(2) Present address: NASA-Langley Research Center, Mail Stop 419, 23665 Hampton, VA, USA;(3) Atmospheric Sciences Division, NASA Langley Research Center, 23665 Hampton, VA, USA |
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Abstract: | The seasonal flux of methane to the atmosphere was measured at three salt marsh sites along a tidal creek. Average soil salinities at the sites ranged from 5 to 17 ppt and fluxes ranged from below detection limits (less than 0.3 mgCH4 m-2 d-1) to 259 mgCH4 m-2 d-1. Annual flux to the atmosphere was 5.6 gCH4 m-2 from the most saline site, 22.4 gCH4 m-2 from the intermediate site, and 18.2 gCH4 m-2 from the freshest of the three sites. Regression of the amount of methane in the soil with flux indicates that changes in this soil methane can account for 64% of the observed variation in flux. Data on pore water distributions of sulfate suggests that the activity of sulfate reducing bacteria is a primary control on methane flux in these transitional environments. Results indicate that relatively high emissions of methane from salt marshes can occur at soil salinities up to approximately 13 ppt. When these data are combined with other tidal marsh studies, annual CH4 flux to the atmosphere shows a strong negative correlation with the long term average soil salinity over a range from essentially fresh water to 26 ppt. |
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Keywords: | methane flux salt marsh salinity gradient |
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