Wetlands as Sinks for Reactive Nitrogen at Continental and Global Scales: A Meta-Analysis
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Wetlands support physical and ecological functions that result in valuable services to society, including removal of reactive nitrogen (Nr) from surface water and groundwater. We compiled published data from wetland studies worldwide to estimate total Nr removal and to evaluate factors that influence removal rates. Over several orders of magnitude in wetland area and Nr loading rates, there is a positive, near-linear relationship between Nr removal and Nr loading. The linear model (null hypothesis) explains the data better than either a model of declining Nr removal efficiency with increasing Nr loading, or a Michaelis–Menten (saturation) model. We estimate that total Nr removal by major classes of wetlands in the contiguous U.S. is approximately 20–21% of the total anthropogenic load of Nr to the region. Worldwide, Nr removal by wetlands is roughly 17% of anthropogenic Nr inputs. Historical loss of 50% of native wetland area suggests an equivalent loss of Nr removal capacity. Expanded protection and large-scale restoration of wetlands should be considered in strategies to re-balance the global nitrogen cycle and mitigate the negative consequences of excess Nr loading.
Key wordsnitrogen reactive nitrogen wetlands denitrification nitrogen removal nitrogen loading
We appreciate the preliminary review by Dan Sobota, and helpful suggestions from anonymous reviewers. The views expressed in this article are those of the authors and do not necessarily reflect the views or policies of the U.S. Environmental Protection Agency. This is contribution 1392 from the Gulf Ecology Division, and a product of EPA’s Ecosystem Services Research Program.
- Armentano TV, Verhoeven JTA. 1990. Biogeochemical cycles: global. In: Patten BC, Ed. Wetlands and shallow continental water bodies, Vol. 1. The Hague, Netherlands: SPB Academic Publishing. p 281–311.Google Scholar
- Axelrad DM, Moore KA, Bender ME. 1976. Nitrogen, phosphorus and carbon flux in Chesapeake Bay marshes. Blacksburg: Virginia Water Resources Research Center, Virginia Polytechnic Institute and State University.Google Scholar
- Cowardin LW, Carter V, Golet FC, LaRoe ET. 1979. Classification of wetlands and deepwater habitats of the United States. Washington, DC: U.S. Department of the Interior, Fish and Wildlife Service.Google Scholar
- Crumpton WG, Goldsborough LG. 1998. Nitrogen transformation and fate in prairie wetlands. Great Plains Res 8:57–72.Google Scholar
- Crumpton WG, Stenback GA, Miller BA, Helmers MJ. 2006. Potential benefits of wetland filters for tile drainage systems: impact on nitrate loads to Mississippi River subbasins. Final project report to U.S. Department of Agriculture Project number: IOW06682, December 2006.Google Scholar
- Dahl TE. 2006. Status and trends of wetlands in the conterminous United States 1998 to 2004. Washington, DC: U.S. Department of the Interior; Fish and Wildlife Service. p 112.Google Scholar
- Mulholland PJ, Helton AM, Poole GC, Hall RO, Hamilton SK, Peterson BJ, Tank JL, Ashkenas LR, Cooper LW, Dahm CN, Dodds WK, Findlay SEG, Gregory SV, Grimm NB, Johnson SL, McDowell WH, Meyer JL, Valett HM, Webster JR, Arango CP, Beaulieu JJ, Bernot MJ, Burgin AJ, Crenshaw CL, Johnson LT, Niederlehner BR, O'Brien JM, Potter JD, Sheibley RW, Sobota DJ, Thomas SM. 2008. Stream denitrification across biomes and its response to anthropogenic nitrate loading. Nature 452:202–6.Google Scholar
- Murray B, Jenkins A, Kramer R, Faulkner SP. 2009. Valuing ecosystem services from wetlands restoration in the Mississippi Alluvial Valley. Nicholas Institute, Duke University NI R 09-02. http://nicholas.duke.edu/institute/msvalley.pdf.
- Richardson CJ, Kadlec JA, Wentz WA, Chamie JPM, Kadlec RH. 1975. Background ecology and the effects of nutrient additions on a central Michigan wetland. Wetlands Ecosystem Research Group, Publ. 4, 52p. NTIS PB-254 336.Google Scholar
- Spiers AG. 2001. Wetland inventory: overview at a global scale. In: Finlayson CM, Davidson NC, Stevenson NJ, Eds. Wetland inventory, assessment and monitoring: practical techniques and identification of major issues. Proceedings of Workshop 4, 2nd International Conference on Wetlands and Development. Australian Department of the Environment and Water Resources, Supervising Scientist Report 161. pp 23–30.Google Scholar
- STAC. 2005. Final report of the Chesapeake Bay Scientific and Technical Advisory Committee’s workshop: understanding “Lag Times” Affecting the Improvement of Water Quality in the Chesapeake Bay. STAC Report 05-001, Chesapeake Research Consortium, Edgewater, Maryland.Google Scholar
- Woodwell GM, Houghton RA, Hall CAS, Whitney DE, Moll RA, Juers DW. 1979. The flax pond ecosystem study: the annual metabolism and nutrient budgets of a salt marsh. In: Jefferies RL, Davy AJ, Eds. Ecological processes in coastal environments. London: Blackwell. p 491–511.Google Scholar