In recent years, the loss and degradation of desert artesian springs has resulted in the loss of endemic species while other species have received “sensitive” designations. Bioassessment procedures have not been developed for groundwater-fed springs in the United States. Assessing the integrity of artesian springs is a challenge because of variable physico-chemical conditions among springs coupled with their unique hydrologic characteristics (a constant inflow of unpolluted water). We collected physico-chemical data and macroinvertebrates from 125 springs. Thirty-three springs clustered into three minimally impacted reference classes. We matched 39 test sites with one of these three classes. An integrated approach combining diversity indices, and aspects of multivariate analyses and multimetrics was more useful than any single method. Multivariate analyses (NMDS, ANOSIM and SIMPER) were particularly helpful in detecting trends at the community level and identifying specific indicator taxa (e.g., amphipods). However, macroinvertebrates in some springs did not respond to the potentially adverse effects of livestock grazing, perhaps because a variety of large ungulates historically frequented these springs (buffalo, elk, deer, etc.). Also, macroinvertebrate diversity increased with increasing disturbance; rare taxa were probably more easily detected as their densities increased with increased food availability in impaired sites. Expanding the scope of this study to artesian springs of the entire Great Basin Province may produce additional reference classes (e.g., > 20°C water temperatures) and provide a way to assess the integrity of all springs.
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Vol. 28 • No. 4