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Presented at the NABS Annual meeting, Athens, Georgia, 2003
in Biogeochemistry II
Relationship between ecosystem metabolism and nitrogen biogeochemical gradients in a stream-lake-stream network
M.M. Bozeman1, M.A. Baker1, and R.O. Hall, Jr.2. 1Department of Biology, Utah State University, Logan, Utah, 84322, 2Department of Zoology and Physiology, University of Wyoming, Laramie, Wyoming, 82071
Surface hydrologic features, such as lakes, can have profound influence on biogeochemical structure and metabolic functioning in catchments. We examined how ecosystem metabolism and nitrogen biogeochemical gradients were related in a stream-lake-stream (S-L-S) network during baseflow. Whole stream and lake metabolism were measured 2-3 times between June and September, 2002 throughout a pristine S-L-S network in Bull Trout catchment, Idaho, USA. Stream reaches were 250-500m from lake connection. A slow water marsh of 460m separated the lake outlet from the outflow stream with metabolism measurements conducted in the first 250m. The lake is 685m from inlet to outlet and metabolism was measured at three sites in the epilimnion. Biogeochemical gradients were determined by duplicate samples taken at 10-50m intervals for 1000m in the inflow and outflow, and at similar intervals within the lake, marsh, and stream-lake mixing zone (delta). Nitrate-N decreased sharply within 24m of the delta from 16.6μgN/L to 2.7μgN/L. Dissolved organic nitrogen continuously increased throughout the S-L-S network with the largest increases occurring between the inflow and delta (14-41μgN/L). Gross primary production nearly doubled from the inflow to outflow, while community respiration showed an opposite trend. Preliminary analyses suggest a solid relationship between N transformation and metabolic rates.
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