Responses of a macroinvertebrate community from a “pristine”, southern British Columbia, Canada, stream to metals in experimental mesocosms. – Environmental Toxicology and Chemistry 18:.
By: John S. Richardson and Peter M. Kiffney
Abstract: Heavy metal contamination is one of the most widespread impacts on surface waters. Experimental, flow-through stream troughs located adjacent to, and receiving water and aquatic invertebrates from, an unmodified, forested stream were used to determine the impact of heavy 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, Pb; 1996 – Cu, Zn) for six days. Benthos and emigration were sampled from each of the 16 troughs. The overall densities of benthos declined, but not significantly as the dose of heavy metals increased. Based on 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. There was no treatment effect on either algal standing crop or bacterial respiration rates. The invertebrates most affected by exposure to heavy metals in this study were species also absent or rare in urban streams nearby.