Phosphorus export from a restored wetland ecosystem in response to natural and experimental hydrologic fluctuations

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Wetland restoration is a commonly used approach to reduce nutrient loading to freshwater and coastal ecosystems, with many wetland restoration efforts occurring in former agricultural fields. Restored wetlands are expected to be effective at retaining or removing both nitrogen and phosphorus (P), yet restoring wetland hydrology to former agricultural fields can lead to the release of legacy fertilizer P. Here, we examined P cycling and export following rewetting of the Timberlake Restoration Project, a 440 ha restored riverine wetland complex in the coastal plain of North Carolina. We also compared P cycling within the restored wetland to two minimally disturbed nearby wetlands and an adjacent active agricultural field. In the restored wetland we observed increased soluble reactive phosphorus (SRP) concentrations following initial flooding, consistent with our expectations that P bound to iron would be released under reducing conditions. SRP concentrations in spring were 2.5 times higher leaving the restored wetland than a forested wetland and an agricultural field. During two large-scale drawdown and rewetting experiments we decreased the water depth by 1 m in ∼10 ha of inundated wetland for 2 weeks, followed by reflooding. Rewetting following experimental drainage had no effect on SRP concentrations in winter, but SRP concentrations did increase when the experiment was repeated during summer. Our best estimates suggest that this restored wetland could release legacy fertilizer P for up to a decade following hydrologic restoration. The time lag between restoration and biogeochemical recovery should be incorporated into management strategies of restored wetlands. Copyright 2010 by the American Geophysical Union.






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Ardón, M, S Montanari, JL Morse, MW Doyle and ES Bernhardt (2010). Phosphorus export from a restored wetland ecosystem in response to natural and experimental hydrologic fluctuations. Journal of Geophysical Research: Biogeosciences, 115(4). p. G04031. 10.1029/2009JG001169 Retrieved from

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Martin Doyle

Professor in the Environmental Sciences and Policy Division

Martin Doyle is a Professor at Duke University focused on the science and policy of rivers and water in the US.  His work ranges from fluid mechanics and sediment transport to infrastructure finance and federal water policy. His first book, The Source (WW Norton, February, 2018), is a history of America’s rivers.  His second book, Streams of Revenue (MIT Press, 2021) is an analysis of ecosystem markets. In addition to his role as a professor, Doyle has had several stints in government: in 2015-2016, he moved to the Department of Interior, where he helped establish the Natural Resources Investment Center, an initiative of the Obama Administration to push forward private investment in water infrastructure, enable water marketing, and increase the use of markets and conservation banks for species conservation.  Prior to that, in 2009-2010, he was the inaugural Frederick J. Clarke Scholar at the US Army Corps of Engineers.  

He has received a Guggenheim Fellowship, an Early Career Award from the National Science Foundation, recognized as a Kavli Fellow for the Frontiers of Science from the National Academy of Sciences and selected to deliver the Gilbert White Lecture by the National Academy of Sciences.


Emily S. Bernhardt

James B. Duke Distinguished Professor

Emily Bernhardt is an ecosystem ecologist and biogeochemist whose research is principally concerned with tracking the movement of elements through ecological systems. Dr. Bernhardt's research aims to document the extent to which the structure and function of aquatic ecosystems is being altered by land use change (urbanization, agriculture, mining) global change (rising CO2, rising sea levels) and chemical pollution. Ultimately this information is necessary to determine whether and how ecosystem change can be mitigated or prevented through active ecosystem management.

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