Wednesday, May 28, 2008 - 9:45 AM
371

Use of δ18O-O2 to model diel community respiration rates in streams

Erin R. Hotchkiss, Program in Ecology, Department of Zoology and Physiology, University of Wyoming, 1000 E. University Ave., Laramie, WY 82071-3166 and Robert O. Hall, Department of Zoology and Physiology, University of Wyoming, Laramie, WY 82071.

Photosynthesis and respiration determine the carbon balance of ecosystems.  There are few ways to measure respiration rates beyond the net change in O2 or CO2 in aquatic systems and, consequently, we often ignore diel fluctuations in our estimates of community respiration.  A central assumption made with most stream metabolism calculations is that respiration rates are constant over a 24-hour period, estimated using the average nighttime O2 consumption rate.  Measurements of δ18O-O2 allow us to test this assumption due to the discrimination against δ18O during mitochondrial respiration.  We sampled three different spring-fed streams in central and western Wyoming over 24-hour periods to monitor the change in day and night δ18O-O2, dO2, light intensity, DOC quantity and quality, and water temperature.  Preliminary results show strong diel cycles in δ18O-O2 in all three streams.  A comparison between δ18O-O2 and traditional in situ O2 methods from one of our most productive sites, Kelly Warm Springs, suggests that daytime community respiration is higher than estimates using average nighttime respiration, likely due to increases in water temperature and/or DOC availability.  We will compare community respiration rates calculated with δ18O-O2, in situ O2, and temperature-adjusted metabolism models for all three streams.


Web Page: community respiration, primary production, stream metabolism

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