抄録
I reviewed the effects of heavy metals, including zinc, on richness and abundance of riverine macroinvertebrate assemblages through results from previous field and experimental studies. Generally, highly polluted streams and rivers have low species richness, reduced abundance of mayflies, and they are dominated by metal-tolerant chironomids. Many studies have reported several metal-sensitive macroinvertebrate metrics such as total taxon richness, abundance and richness of mayflies, EPT richness（the number of taxa in the orders Ephemeroptera, Plecoptera and Trichoptera），and abundance of heptageniids. Furthermore, the safe concentrations of zinc, not mitigating the significant effects on five macroinvertebrate community metrics（total taxon richness, total abundance, EPT richness, and richness and abundance of mayflies）, were collected from the literature. The lower values of the safe concentrations were 20-50 μg/L, well comparable to the Japanese zinc standard for freshwater（30 μg/L）. It should be noted that the safe concentrations may be conservative estimates since most of the previous studies, reviewed here, were performed under the multiple metals contamination. Ecological risk assessment only based on laboratory toxicity tests has several limitations to extrapolate its results to the natural environments. Thus, information on the safe concentrations, obtained from studies conducted under more realistic conditions（e.g., field survey）, would be valuable for more effective ecological risk management.
