Anaerobic Metabolism in Tidal Freshwater Wetlands: I. Plant Removal Effects on Iron Reduction and Methanogenesis
- 697 Downloads
For energetic reasons, iron reduction suppresses methanogenesis in tidal freshwater wetlands; however, when iron reduction is limited by iron oxide availability, methanogenesis dominates anaerobic carbon mineralization. Plants can mediate this microbial competition by releasing oxygen into the rhizosphere and supplying oxidized iron for iron reducers. We utilized a plant removal experiment in two wetland sites to test the hypothesis that, in the absence of plants, rates of iron reduction would be diminished, allowing methanogenesis to dominate anaerobic metabolism. In both sites, methanogenesis was the primary anaerobic mineralization pathway, with iron reduction dominating only early and late in the growing season in the site with a less organic soil. These patterns were not influenced by the presence of plants, demonstrating that plants were not a key control of microbial metabolism. Instead, we suggest that site conditions, including soil chemistry, and temperature are important controls of the pathways of anaerobic metabolism.
KeywordsAnaerobic microbial metabolism Iron reduction Jug Bay Wetlands Sanctuary, Maryland, USA Methane Plant removal Tidal freshwater wetland
Chris Swarth at the Jug Bay Wetlands Sanctuary allowed unfettered access to our research sites for this project. We thank Jim Duls, Nick Mudd, Lucinda Williams, Pamela Weisenhorn, Sara McQueeney, Kyle Chambers, and Eric Pfoutz for assistance with field and laboratory work on this project. Comments from two anonymous reviewers greatly improved this manuscript. This research was supported by NSF DEB-0516400 to JPM and Smithsonian Post-Doctoral Fellowships to JKK and AES-G.
- Bullock A., A.E. Sutton-Grier, and J.P. Megonigal 2012. Anaerobic metabolism in tidal freswhater wetlands: II. Temperature sensitivy of microbial iron cycling. Estuaries and Coasts. doi: 10.1007/s12237-012-9536-5.
- Denman K.L., et al. 2007. Couplings Between Changes in the Climate System and Biogeochemistry. In Climate Change 2007: The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change eds Solomon S, D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M.Tignor and H.L. Miller, Cambridge, United Kingdom and New York, NY, USA: Cambridge University Press.Google Scholar
- Eaton A.D., L.S. Clesceri, and A.E. Greenberg. 1995. Standard methods for the examination of water and wastewater. Washington, DC: American Public Health Association.Google Scholar
- Emerson D., W. Bellows, J.K. Keller, A.E. Sutton-Grier, and J.P. Megonigal. 2012. Anaerobic metabolism in tidal freswhater wetlands: III. Effects of plant removal on Archaeal microbial communities. Estuaries and Coasts. doi: 10.1007/s12237-012-9496-9.
- Forster, P., V. Ramaswamy, P. Artaxo, T. Berntsen, R. Betts, D.W. Fahey, J. Haywood, J. Lean, D.C. Lowe, G. Myhre, J. Nganga, R. Prinn, G. Raga, M. Schulz, and R. Van Dorland. 2007. Changes in atmospheric constituents and in radiative forcing. In Climate change 2007: The physical science basis. Contribution of working group I to the fourth assessment report of the intergovernmental panel on climate change, eds. Solomon, S., D. Qin, M. Manning, Z. Chen, M. Marquis, K.B. Averyt, M. Tignor and H.L. Miller, Cambridge, United Kingdom and New York, NY, USA: Cambridge University Press.Google Scholar
- Lovley, D.R., and E.J.P. Phillips. 1986a. Organic matter mineralization with reduction of ferric iron in anaerobic sediments. Applied and Environmental Microbiology 51: 683–689.Google Scholar
- Lovley, D.R., and E.J.P. Phillips. 1986b. Availability of ferric iron for microbial reduction in bottom sediments of the freshwater tidal Potomac River. Applied and Environmental Microbiology 52: 751–757.Google Scholar
- Marsh A.S., D.P. Rasse, B.G. Drake, and J.P. Megonigal. 2005. Effect of elevated CO2 on carbon pools and fluxes in a brackish marsh. Estuaries 28: 694–704.Google Scholar
- Megonigal J.P., and S.C. Neubauer. 2009. Biogeochemistry of tidal freshwater wetlands. In Coastal wetlands: an integrated ecosystem approach, eds Perillo G, Wolanski E, Cahoon D, Brinson M, Elsevier.Google Scholar
- Megonigal, J.P., M.E. Hines, and P.T. Visscher. 2004. Anaerobic metabolism: linkages to trace gases and aerobic processes. In Biogeochemistry, ed. W.H. Schlesinger, 317–424. Oxford: Elsevier-Pergamon.Google Scholar
- Whigham D.F. 2009. Primary production in tidal freshwater wetlands. In Tidal Freshwater Wetlands, eds Barendregt A, Whigham D, Baldwin A, 115-122. Backhuys Publishers, Leiden; Margraf Publishers, Weikersheim.Google Scholar
- Windham-Myers L., M. Marvin-Dipasquale, D.P. Krabbenhoft, J.L. Agee, M.H. Cox, P. Heredia-Middleton, C. Coates, and E. Kakouros. 2009. Experimental removal of wetland emergent vegetation leads to decreased methylmercury production in surface sediments. Journal of Geophysical Research 114: G00C05.Google Scholar