title: Ecological engineering practices for the reduction of excess nitrogen in human-influenced landscapes: a guide for watershed managers.
abstract: Excess nitrogen (N) in freshwater systems, estuaries, and coastal areas has well-documented deleterious effects on ecosystems. Ecological engineering practices (EEPs) may be effective at decreasing nonpoint source N leaching to surface and groundwater. However, few studies have synthesized current knowledge about the functioning principles, performance, and cost of common EEPs used to mitigate N pollution at the watershed scale. Our review describes seven EEPs known to decrease N to help watershed managers select the most effective techniques from among the following approaches: advanced-treatment septic systems, low-impact development (LID) structures, permeable reactive barriers, treatment wetlands, riparian buffers, artificial lakes and reservoirs, and stream restoration. Our results show a broad range of N-removal effectiveness but suggest that all techniques could be optimized for N removal by promoting and sustaining conditions conducive to biological transformations (e.g., denitrification). Generally, N-removal efficiency is particularly affected by hydraulic residence time, organic carbon availability, and establishment of anaerobic conditions. There remains a critical need for systematic empirical studies documenting N-removal efficiency among EEPs and potential environmental and economic tradeoffs associated with the widespread use of these techniques. Under current trajectories of N inputs, land use, and climate change, ecological engineering alone may be insufficient to manage N in many watersheds, suggesting that N-pollution source prevention remains a critical need. Improved understanding of N-removal effectiveness and modeling efforts will be critical in building decision support tools to help guide the selection and application of best EEPs for N management.
authors.affiliation: Plant and Microbial Biology, University of California at Berkeley, Berkeley, CA 94720, USA. epasseport@gmail.com
authors.forename: Elodie
authors.initials: E
authors.lastname: Passeport
authors.forename: Philippe
authors.initials: P
authors.lastname: Vidon
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Forshay
authors.forename: Lora
authors.initials: L
authors.lastname: Harris
authors.forename: Sujay S
authors.initials: SS
authors.lastname: Kaushal
authors.forename: Dorothy Q
authors.initials: DQ
authors.lastname: Kellogg
authors.forename: Julia
authors.initials: J
authors.lastname: Lazar
authors.forename: Paul
authors.initials: P
authors.lastname: Mayer
authors.forename: Emilie K
authors.initials: EK
authors.lastname: Stander
mesh_terms: D004463:Ecology; D017753:Ecosystem; D009584:Nitrogen / Q000302:isolation & purification*; D014874:Water Pollutants, Chemical / Q000302:isolation & purification; D014881:Water Supply / Q000032:analysis*; D053833:Wetlands
chemical_list: D014874:Water Pollutants, Chemical; D009584:Nitrogen