PARENT SESSION
Oral Session #65: Aquatic Ecology: Stream and Lake.
Presiding: C. Osenberg
Wednesday, August 7. 1:00 PM to 4:45 PM. Coconino Meeting Room, TCC.
Upland disturbance and in-stream processes: Patterns of stream metabolism along a disturbance gradient.
Houser, Jeffrey*,1, Mulholland, Patrick1, Maloney, Kelly2, 1 Oak Ridge National Lab, Oak Ridge, Tennessee2 Auburn University, Auburn, Alabama
ABSTRACT- Because watershed characteristics affect the inputs of sediments and nutrients into streams, watershed disturbances can affect in-stream processes. Spatial variability in the intensity of military training (infantry and tank maneuvers) at the Ft. Benning military base (Columbus, GA) results in the uplands of some stream catchments being highly disturbed while others remain relatively undisturbed. We used this disturbance gradient to test the hypothesis that upland disturbance reduces in-stream metabolism due to reduced stability of stream substrata and reduced organic matter content of the stream bottom. We selected 11 stream sites located in 11 different catchments: 3 reference sites, 4 sites of low to moderate disturbance, and 4 sites of high disturbance. During storm events, larger increases in suspended sediments (standardized to the magnitude of the increase in stream flow and baseflow concentrations) occurred in the disturbed sites compared to the reference sites. During the summer, rates of in-stream respiration were higher at the reference sites (2 - 4 g m-2 d-1), and lower at the highly disturbed sites (~0 - 1.5 g (2 - 4 g m-2 d-1). At the reference and low disturbance sites, in-stream respiration was higher during the winter relative to summer, whereas in the high disturbance systems winter respiration rates were similar to summer rates, remaining lower than the rates observed in the reference sites. These results add to our growing understanding of the important connections between watershed characteristics, land use and in-stream processes.
KEY WORDS: metabolism, respiration, stream, watershed