Monday, June 4, 2007 - 2:15 PM
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Recovery trajectories of prairie streams following drought

Justin N. Murdock1, Katie N. Bertrand1, Keith B. Gido1, Walter K. Dodds1, and Matt R. Whiles2. (1) Division of Biology, Kansas State University, 116 Ackert Hall, Manhattan, KS 66506, (2) Department of Zoology, Southern Illinois University, Carbondale, IL 62901

Changes in stream hydrology from water withdrawal, watershed development, or altered local climate can modify the timing and intensity of drying.  Ecosystem recovery from drying may be influenced by the return patterns of certain functional feeding groups or changes in biotic resource availability at the onset of recovery. Experimental streams were used to investigate the influence of drying intensity (completely dry or isolated pools) and fish presence (benthic grazers and water column omnivores) on stream structural and functional recovery over nine weeks. Streams that dried completely had a delayed (by 2 weeks), but similar (76 vs 72 mg chl a m-2) peak algal biomass in pools, and consistently higher, but not significant, biomass in riffles (116 vs 92 mg chl a m-2). Functionally, dried streams had lower initial nutrient uptake rates until day 18 (p < 0.001), then equalized among treatments. The influence of fish on net ecosystem production and community respiration trajectories varied significantly with time since rewetting. Drying intensity had a greater direct effect on recovery, but significant interaction effects of fish with days since rewetting suggests the timing of species reintroduction may be important to the functional recovery of the stream.