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Presented at the NABS Annual meeting, Athens, Georgia, 2003
in Biogeochemistry I
Dissolved nitrogen dynamics in a coupled stream-lake ecosystem during snowmelt quantified using 15-N nitrate
M.A. Baker1, R.O. Hall, Jr.2, W.A. Wursbaugh1, M.M. Bozeman1, and C.D. Arp1. 1Ecology Center, Utah State University, Logan Utah, USA 84322, 2Dept. of Zoology and Physiology, University of Wyoming, Laramie, Wy, 82710
Small streams are important landscape features because of their ability to take up and transform inorganic nutrients. In glaciated landscapes, streams are intersected by lakes, and this hydrologic connectivity may impact nutrient dynamics. We performed a two week release of 15N-nitrate during snowmelt in the inflow stream of Bull Trout Lake, Idaho. We expected that at this time, the inflow stream would act as a pipe, with little nitrate uptake. After 3 days, nitrate uptake length was 7800 m, but the mass transfer coefficient was 2.0 mm/min, and about 20% of added 15N-nitrate was removed in the inflow stream. By Day 14, uptake length was 4300 m and mass transfer coefficient was 2.6 mm/min. On all sample dates, the lake took up the balance of added tracer; no labeled nitrate was detected at the first sample location in the outflow stream. NO3 was regenerated during transport in the outflow. Regeneration of 15N-NO3 in the inflow following the addition was low and more tracer was detected as DON. Even during cold floods, small streams have higher than expected capacity to take up added nutrients and the presence of lakes in watersheds can greatly impact dissolved nutrients.
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