The effects of elevated metals on stream periphyton in the Eagle River, a mining impacted river in central Colorado, were assessed in 1991 and 1992 using assemblage information (taxa richness, community similarity) and non-taxonomic measures (biomass, chlorophyll a, autotrophic index). The number of periphyton genera collected ranged from 2 at a site adjacent to abandoned mining operations to 21 at a downstream site, but was not significantly correlated with dissolved metals concentrations. Fragilaria and Achnanthes were the dominant genera at all sites, with Fragilaria dominating the less impacted sites and Achnanthes dominating at the more impacted sites. Taxonomic similarity was greatest among those sites receiving the greatest [...]