“Caddisfly watch,” a biomonitoring program using Stenopsyche larvae to determine radioactive cesium contamination in rivers following the Fukushima nuclear disaster

The “Caddisfly Watch” program proposes the use of larvae of the caddisfly genus Stenopsyche (Trichoptera: Stenopsychidae) to monitor the radioactive cesium (137Cs) pollution, including that of suspended solids, in river environments, as a simple method was essential for this following the Fukushima nuclear disaster in March 2011. A variety of aquatic organisms were collected from rivers in Japan in 2012 and their levels of radioactive Cs measured. Amongst all the organisms collected, the highest concentrations of 137Cs were observed in caddisfly larvae. These larvae occur at a high density and can be collected at regular intervals in most rivers throughout Japan. It is proposed that caddisfly larvae can be used as bioindicators of radioactive Cs contamination in rivers, as their temporal and spatial changes are easily assessed.