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Presented at the NABS Annual meeting, Anchorage, Alaska, 2006
in Disturbance Ecology 2
Macroinvertebrate community response to streamflow diversion magnitude in Rocky Mountain streams
C.M. Albano1, N.L. Poff1, D.W. Baker2, and B.P. Bledsoe2.1Department of Biology, Colorado State University, Fort Collins, CO 80523, 2Department of Civil Engineering, Colorado State University, Fort Collins, CO 80523
In the Rocky Mountains, water diversions from headwater streams are a ubiquitous source of streamflow alteration. Previous research has indicated that moderate diversions (∼50% flow abstracted) minimally impact macroinvertebrate community structure and functional diversity, whereas more severe diversions (∼95% abstracted) result in significant ecological impairment. The purpose of this research is to 1) identify the magnitude of diversion at which a dramatic increase in macroinvertebrate community impairment occurs and 2) evaluate resulting changes in functional composition in terms of macroinvertebrate species traits. We examined the response of macroinvertebrate communities to diversions in 14 headwater streams spanning a gradient from 1-99% abstracted in northern Colorado and southern Wyoming. Macroinvertebrates were collected above and below each diversion structure in Summer and Fall, 2005. Measures of macroinvertebrate community structure and function were contrasted above and below each diversion. We predicted that a significant reduction in richness and abundance of macroinvertebrates would occur in streams with diversions exceeding 50% of ambient discharge and that this response would be amplified in streams with increasing diversion magnitude. Further, we hypothesized that the elimination of species with traits that are sensitive to the specific habitat alterations associated with reduced flow conditions would explain the observed community changes.
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