| Abstrakt: |
Metal contamination is one of the most widespread impacts on surfacewaters. Experimental flumes receiving water and aquatic invertebrates from an undisturbed, forested stream were used to determine the impact of metals in a low-conductivity stream. The experimental flumes were exposed to a gradient of doses maintaining a constant ratio of metals (1995: Cu, Zn, Mn, and Pb; 1996: Cu and Zn) for 6 d. Benthos andemigration were sampled from each of the 16 troughs. The overall densities of benthos declined, but not significantly, as the dose of metals increased. On the basis of the slopes of the concentration-response curve, Baetis, Ameletus, and Paraleptophlebia were the most sensitive taxa present. Other taxa (e.g., Nemouridae and Oligochaeta) were mildly affected by high metal concentrations. Chironomidae showed no significant decrease in densities with increasing dose. Chironomids made up >80% of the benthos and is the primary reason for no significant dose effect on overall densities. No treatment effect was observedon either algal standing crop or bacterial respiration rates. The invertebrate genera most affected by exposure to metals in this study were also absent or rare in nearby urban streams with high metal concentrations. [ABSTRACT FROM AUTHOR] |
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