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Presented at the NABS Annual meeting, Pittsburgh, Pennsylvania, 2002
in Disturbance Ecology IV
THE EFFECT OF A SUDDEN FLOW REDUCTION ON AQUATIC INSECTS OF THE UPPER YAKIMA RIVER, WASHINGTON, USA.
C.P. Arango1 and E.B. Snyder2. 1Department of Geography, Central Washington University, Ellensburg, WA, USA 98926, 2Department of Biology, Central Michigan University, Mt. Pleasant, MI, USA 48859
The Yakima River, a regulated river in south-central Washington, undergoes an annual sudden flow reduction called flip-flop. By sampling aquatic insects on the upper Yakima River near Ellensburg before, during, and after flip-flop during late summer 2000, I found: 1) decreased benthic diversity after flow reduction; 2) aquatic insect stranding after shoreline exposure; and 3) increasing drift density throughout flip-flop. Flow regime establishes the shifting habitat mosaic that riverine biota exploit, thus regulation can fundamentally alter ecosystem structure and function. Through time, community composition may shift as insects prone to drift, like Simuliidae and Baetidae, increase while less mobile insects, like Tipulidae and Glossossomatidae, decrease. Future research should elaborate flip-flop’s effect on aquatic vegetation, fisheries, and food web dynamics in this and other reaches. Water conservation measures may mitigate flip-flop’s effect, but a primary consideration should be eliminating flip-flop and establishing a normative flow regime.
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