Hydrologic control of nitrogen removal, storage, and export in a mountain stream

Limnology and Oceanography
By: , and 

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Abstract

Nutrient cycling and export in streams and rivers should vary with flow regime, yet most studies of stream nutrient transformation do not include hydrologic variability. We used a stable isotope tracer of nitrogen (15N) to measure nitrate (NO3) uptake, storage, and export in a mountain stream, Spring Creek, Idaho, U.S.A. We conducted two tracer tests of 2‐week duration during snowmelt and baseflow. Dissolved and particulate forms of 15N were monitored over three seasons to test the hypothesis that stream N cycling would be dominated by export during floods, and storage during low flow. Floods exported more N than during baseflow conditions; however, snowmelt floods had higher than expected demand for NO3 because of hyporheic exchange. residence times of benthic N during both tracer tests were longer than 100 d for ephemeral pools such as benthic algae and wood biofilms. Residence times were much longer in fine detritus, insects, and the particulate N from the hyporheic zone, showing that assimilation and hydrologic storage can be important mechanisms for retaining particulate N. Of the tracer N stored in the stream, the primary form of export was via seston during periods of high flows, produced by summer rainstorms or spring snowmelt the following year. Spring Creek is not necessarily a conduit for nutrients during high flow; hydrologic exchange between the stream and its valley represents an important storage mechanism.

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Publication type Article
Publication Subtype Journal Article
Title Hydrologic control of nitrogen removal, storage, and export in a mountain stream
Series title Limnology and Oceanography
DOI 10.4319/lo.2009.54.6.2128
Volume 54
Issue 6
Year Published 2009
Language English
Publisher American Society of Limnology and Oceanography
Description 15 p.
First page 2128
Last page 2142
Country United States
State Idaho
Other Geospatial Spring Creek
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