Event Title

Biologic and Hydrologic Controls on Nitrogen Cycling in Mountain Watersheds: Results of Ecosystem N15 Stable Isotope Tracer Additions

Location

Space Dynamics Laboratory

Event Website

http://water.usu.edu/

Start Date

3-26-2004 9:00 AM

End Date

3-26-2004 9:15 AM

Description

How is nitrate retained, transformed, and transported downstream by stream-lake linkages in mountain watersheds with relatively low nitrate inputs? The answer is important for understanding the effects of elevated N deposition on lakes and streams in impacted regions. We addressed this question with two-week releases of 15N-nitrate to the inflow stream of Bull Trout Lake (Sawtooth Range, Idaho) during both snowmelt and baseflow, when stream nitrate concentrations were near 10 and 4 microg N/L, respectively. The inflow stream took up 30% and 74% of the N15-nitrate addition during the snowmelt and baseflow experiments, respectively. Most of this N15 uptake was via hydrologic loss to the floodplain and not via biological processes. For both additions, the lake took up the remaining N15-nitrate and none was detected in the outflow. Only about 2-8% of the N15 left the lake as seston (algae, bacteria, and detritus) and very little (

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Mar 26th, 9:00 AM Mar 26th, 9:15 AM

Biologic and Hydrologic Controls on Nitrogen Cycling in Mountain Watersheds: Results of Ecosystem N15 Stable Isotope Tracer Additions

Space Dynamics Laboratory

How is nitrate retained, transformed, and transported downstream by stream-lake linkages in mountain watersheds with relatively low nitrate inputs? The answer is important for understanding the effects of elevated N deposition on lakes and streams in impacted regions. We addressed this question with two-week releases of 15N-nitrate to the inflow stream of Bull Trout Lake (Sawtooth Range, Idaho) during both snowmelt and baseflow, when stream nitrate concentrations were near 10 and 4 microg N/L, respectively. The inflow stream took up 30% and 74% of the N15-nitrate addition during the snowmelt and baseflow experiments, respectively. Most of this N15 uptake was via hydrologic loss to the floodplain and not via biological processes. For both additions, the lake took up the remaining N15-nitrate and none was detected in the outflow. Only about 2-8% of the N15 left the lake as seston (algae, bacteria, and detritus) and very little (

https://digitalcommons.usu.edu/runoff/2004/AllAbstracts/32