Hydrologic control of nitrogenremoval, storage and export in a mountain stream

Authors

R. O. Hall Jr.
Michelle A. Baker, Utah State UniversityFollow
C. D. Arp
B. J. Koch

Document Type

Article

Journal/Book Title/Conference

Limnology and Oceanography

Volume

54

Publication Date

2009

First Page

2128

Last Page

2142

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.

Recommended Citation

Hall, R.O. Jr., M.A Baker, C.D. Arp*, and B.J. Koch*. 2009. Hydrologic control of nitrogen removal, storage and export in a mountain stream. Limnology and Oceanography 54:2128-2142.