Trace element bioaccumulation was studied in immature benthic insects from two contaminated river systems to develop these animals as bioindicators. In one river, Cu, Cd, Pb, and Zn were analysed in insects and in fine bed sediments over a 381-km reach downstream of a large copper mining complex. In the other river, As contamination from a gold mine was assessed in insects and bed sediments over a 40-km reach. All insect taxa collected in contaminated river reaches had elevated whole-body trace element concentrations. However, direct comparisons of contamination using a single, common species among stations were limited because few species were distributed throughout the study reaches. Comparisons of contamination at taxomic levels higher than species were complicated by element-specific differences in bioaccumulation among taxa. These differences appeared to be governed by biological and hydrogeochemical factors. The variation in element concentrations among species of the caddisfly Hydropsyche was slightly greater than within individual species. If this genus is representative of others, comparisons of contamination within genera may be a practical alternative for biomonitoring studies when single species are not available.

1. The relationships between three habitat scales and lotic invertebrate species composition were investigated for the 15 540 km2 Yakima River basin in south‐central Washington, U.S.A. 2. The three spatial scales were sample (the sampled riffle), reach (a length of ten–twenty stream widths) and segment (a length of stream of nearly uniform slope and valley form having no change in stream order). 3. Physical variables were highly correlated between scales and expressed a relationship between altitude, basin form and small‐scale physical structure. 4. Multiple discriminant function analyses indicated that segment‐ and reach‐scale variables discriminated among species‐defined groups better than sample‐scale variables. 5. Species composition varied along a complex altitudinal gradient of changing basin form and resultant land use. 6. There was no clear relationship between species richness and altitude on a site basis. However, when viewed at the basin scale, maximum richness was observed at the transition between montane and valley sites.

1. Effects of copper on species composition and production of benthic insects in an oligotrophic stream dosed at low concentrations {2.5-15 ^g 1"' Cu,; approximately 12-75 ng I"' Cu-+) were determined. Dosing was initially in autumn-early winter when peak densities of many species occur. It was resumed the following summer near the time of egg hatch of most species and continued through the remaining aquatic stages of univoltine and multivoltine taxa.2. Declines in population density of species representing all major orders {Ephemeroptera. Plecoptera, Coleoptera. Trichoptera and Diptera) occurred at 5 and/or 10 /^g 1"' Cu^. Differences in sensitivity among families existed in the Plecoptera, Trichoptera and Diptera. These differences were apparently related to the trophic preferences of taxa, with herbivores and detritivores more sensitive than predators.3. Equivalent percentage declines in annual production occurred for herbivores/detritivores and predators exposed to copper, suggesting an adjustment in total predator production in response to the reduction in prey abundance.4. Possible examples of reiease of benthic insects from competition with less tolerant species were rare. Of the thirty-seven most abundant taxa, only the predators Rhyacophila vaccua and Rhyacophila angelita were more abundant [than in the control] at copper concentrations (5 and 10//gl"' Cuj) causing population declines of other species. 5. Species richness and percentage similarity were sensitive communitylevel indices of copper toxicity, whereas Brillouin's diversity was insensitive to differences among the control and copper-treated stream sections.

No abstract

A biomonitoring technique was employed to complement studies of metal transport in the upper Sacramento River affected by acid mine drainage. Metals (Al, Cd, Cu, Fe, Hg, Pb, and Zn) were determined in a resident invertebrate, Hydropsyche californica (Insecta: Trichoptera), and streambed sediments (<62 µm) to assess metal contamination within a 111-km section of the river downstream of the mining area. Metals in H. californica also were interpreted to be broadly indicative of metal exposure in fish. Total Hg was determined in the whole body of the insect, whereas Al, Cd, Cu, Fe, Pb, and Zn were additionally separated into operationally defined cytosolic (used as an indicator of exposure to bioavailable metal) and particulate fractions. Total concentrations of Cd, Cu, Hg, Pb, and Zn in sediments were consistent with documented upstream sources of acid mine drainage. Metal distribution patterns in H. californica and sediments were generally consistent for Cd, Cu, and Pb but inconsistent for Hg and Zn. Concentrations in H. californica indicated that bioavailable Cd, Cu, Pb, and Zn was transported at least 120 km downstream of the mine sources. Zinc in H. californica was elevated, but unlike sediments, did not decrease downstream. Mercury in H. californica was not elevated.