CS34 River Dynamics
Date: Wednesday, June 12, 2002
Time: 2:15:00 PM
Location: View Royal
 
StelzerRS, University of Wisconsin Oshkosh, Oshkosh, USA, stelzer@uwosh.edu
Bernhardt, E, S, Duke University, Durham, USA, ebernhar@duke.edu
 
A COMPARISON OF OPEN-CHANNEL AND CHAMBER METHODS FOR ESTIMATING WHOLE STREAM METABOLISM IN A NORTH TEMPERATE STREAM
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We compared open-channel and chamber methods for estimating whole-stream metabolism in a forested 280-m reach of Wappinger Cr., NY. Open-channel metabolism (2-station and single station) was calculated from continuous measurements of dissolved oxygen, and reaeration rates, which were determined from injections of SF6. Metabolic rates of surface sediments placed in chambers were used to construct photosynthesis-irradiance curves. We used the P-I curves in conjunction with continuous light measurements in the reach to extrapolate the chamber rates to the whole stream reach. Two-station and single-station estimates of gross primary production (GPP) and community respiration (CR) were within 25% of each other. GPP in the reach based on extrapolations from chambers underestimated GPP based on open-channel methods by 28-48%. CR was 50-60% lower using the chamber methods compared to open-channel techniques. Finally, net ecosystem production (NEP) based on chambers was 26-74% higher than estimates using the open-channel methods. Higher values of NEP from chambers compared to open-channel methods suggest that hyporheic respiration may contribute significantly to whole-stream metabolism in Wappinger Cr.