Abstract
Trace element contaminations were monitored in a stream by using of the larvae of an aquatic insect, caddisfly Stenopsyche marmorata as a bio-monitor of trace element contamination every other year from April 1979 to April 1989. The caddisfly was distributed widely in rivers and streams in Japan. In April 1989, high concentrations of cadmium and copper in the larvae which seemed to be caused by a factory waste water were detected. Accordingly, concentrations of trace elements in water, sediments, periphytons (substances adhering onto the river bed) and the larvae were mesured.
The concentrations of cadmium and copper in the larvae were higer than those of water, sediments, or periphytons of the stream. When discharge of the waste water from a factory which was the pollution source was stopped, the concentrations of both elements in the larvae gradually decreased with time elapsed, finally reaching to the background levels after one year.
These findings indicate that the caddisfly larvae can be used as a good bio-monitor for detection of low level contaminations of trace elements in rivers, of which sensitive detection with water, sediments and periphytons is offen very difficult.
