Effects of subacute cadmium exposure on a hardwater mountain stream microcosm

Abstract

Open stream microcosms in the RIFFLE facility were exposed to 22 μg l −1 cadmium for 21 days. Although less than 0.3% of the metal passing through the streams remained in the microcosms, more than 1000 μg g −1 dry wt accumulated in the Aufwuchs community, apparently in response to photosynthetically induced CdCO 3 precipitation. Accumulation decreased with increasing trophic level in the order: Aufwuchs > macrophytes > grazers/collectors > predators. Although no effect on periphyton community structure was observed, invertebrate grazers and collectors in the riffles were adversely affected by cadmium exposure, while populations of pool chronomida and riffle predators increased. Open lotic microcosms are shown to provide valuable hypotheses regarding metal fate and effects, but cannot be used as simple screening tools because of the nature of the invertebrate population data likely to be produced.