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ASSOCIATIONS AMONG CATCHMENT- AND SITE-SCALE DISTURBANCE INDICATORS AND BIOLOGICAL ASSEMBLAGES AT LEAST- AND MOST-DISTURBED STREAM AND RIVER SITES IN THE WESTERN UNITED STATES
Citation:
WHITTIER, T. R., J. L. STODDARD, R. M. HUGHES, AND G. A. LOMNICKY. ASSOCIATIONS AMONG CATCHMENT- AND SITE-SCALE DISTURBANCE INDICATORS AND BIOLOGICAL ASSEMBLAGES AT LEAST- AND MOST-DISTURBED STREAM AND RIVER SITES IN THE WESTERN UNITED STATES. Chapter 48, American Fisheries Society Symposium. American Fisheries Society, Bethesda, MD, , 641-664, (2006).
Impact/Purpose:
To define least-disturbed and most-disturbed conditions for a set of water chemistry, catchment, and site-scale indicators of disturbance and associate them with vertebrate assemblages
Description:
At broad scales, the types and intensities of human disturbances to ecosystems vary along natural gradients. Biological assemblages also vary with natural and human disturbance gradients. We defined least-disturbed conditions for a set of water chemistry, catchment, and site-scale indicators of disturbance, for 835 Environmental Monitoring and Assessment Program sites in the Mountains, Xeric, and Plains regions of 12 conterminous western United States. For each disturbance indicator, the definition of least-disturbed condition for phosphorus in eastern Plains streams allowed up to 100 µg/L total phosphorus, while in western Plains streams, less than 30 µg/L total phosphorus was required. Sites were scored by the number of times they met the least-disturbed condition for all disturbance indicators. We also applied this process to score for most-disturbed condition. The importance of disturbance types varied regionally and along natural gradients. For example, catchment-scale disturbance measures did not distinguish between least- and most-disturbed sites for small streams at higher elevations, but were important for larger streams and at lower elevations. We examined regional-scale patterns in aquatic vertebrate species and assemblage metrics, and macrobenthos assemblage metrics at least- and most-disturbed sites. Most-disturbed sites in the Mountains and Xerix regions had higher proportions of nonnative and tolerant vertebrates and noninsect macrobenthos, and lower proportions of Ephemeroptera, Plecoptera, and Trichoptera individuals and taxa than did the least-disturbed sites. The Plains region has been extensively used by humans and showed less contrast between disturbance classes for most of these measures.