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Nutrient Retention in Restored Streams and Floodplains: A Review and Synthesis
Citation:
Newcomer-Johnson, T., S. Kaushal, P. Mayer, R. Smith, AND G. Sivirichi. Nutrient Retention in Restored Streams and Floodplains: A Review and Synthesis. WATER. MDPI, Basel, Switzerland, 8(4):116, (2016).
Impact/Purpose:
Excess nitrogen and phosphorus from human activities contributes to the degradation of water quality in streams and coastal areas nationally and globally. Restoring streams and floodplains may be an important management approach to improve water quality by increasing the capacity of streams and water bodies to process and/or remove nitrogen and phosphorus. However, the efficacy of restoration methods varies widely, leading to uncertainty about which approach is more effective and under what circumstances. We conducted a literature review of restoration effectiveness among 79 published studies. Overall, 62% of results were positive, 26% were neutral, and 12% were negative with respect to nitrogen and phosphorous management and reduction. We did a further intensive meta-analysis on studies employing nutrient spiraling methods, reviewing 240 experimental additions of ammonium, nitrate, and soluble reactive phosphorus. Effectiveness in rates of uptake and removal were highly variable over space and time but showed that the size of the stream restoration (total surface area) and hydrologic residence time were the most important drivers influencing nutrient uptake. Our study is intended to provide guidance for watershed managers to select the most cost effective approaches for nutrient management under various conditions.
Description:
Abstract: Excess nitrogen (N) and phosphorus (P) from human activities have contributed to degradation of coastal waters globally. A growing body of work suggests that hydrologically restoring streams and floodplains in agricultural and urban watersheds has potential to increase nitrogen and phosphorus retention, but rates and mechanisms have not yet been synthesized and compared across studies. We conducted a review of nutrient retention within hydrologically reconnected streams and floodplains including 79 studies. Overall, 62% of results were positive, 26% were neutral, and 12% were negative. The studies we reviewed used a variety of methods to analyze nutrients cycling. We did a further intensive meta-analysis on nutrient spiraling studies because this method was the most consistent and comparable between studies. A meta-analysis of 240 experimental additions of ammonium (NH4+), nitrate (NO3-), and soluble reactive phosphorus (SRP) was synthesized from 15 nutrient spiraling studies. Overall, we found that rates of uptake were variable along stream reaches over space and time. Our results indicate that the size of the stream restoration (total surface area) and hydrologic residence time can be key drivers in influencing N and P uptake at broader watershed scales or along the urban watershed continuum.
