Anaerobic Metabolism in Tidal Freshwater Wetlands: III. Temperature Regulation of Iron Cycling
Understanding the ecological processes that regulate the production and fate of methane (CH4) in wetland soils is essential for forecasting wetland CH4 emissions. Iron reduction is an important carbon mineralization pathway that is capable of suppressing CH4 production in freshwater wetlands, but our understanding of temperature regulation of iron oxide respiration and the subsequent impacts on CH4 production is limited. We tested the hypothesis that temperature regulates iron reduction rates indirectly through differential effects on Fe(II) oxidation versus Fe(III) reduction, which ultimately determines the size of the microbially labile, poorly crystalline Fe(III) pool. Our study indicates that rates of iron reduction are more sensitive to changes in temperature than rates of iron oxidation, which creates imbalance in the relative proportion of Fe(II) and Fe(III) in the poorly crystalline soil iron pool as temperatures change. Our results suggest that warmer temperatures can cause the Fe(III) oxide pool to decline, limiting the Fe(III) supply to iron reducers and relieving competition for organic carbon with methanogens.
KeywordsIron cycling Iron oxidation Iron reduction Microbial respiration Tidal freshwater wetland Temperature response Jug Bay Sanctuary
We thank Jug Bay Wetlands Sanctuary for providing access to the study site; Cindy Gilmour, Wayne Coats, and Pat Neale for the use of the incubators and the SERC Science and Coffee Discussion Group for feedback on experimental design. Thanks to Andrew Graham for helping with figures and statistics and Jason Keller for comments and advice. This work was funded by NSF DEB-0516400 to JPM.
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