BIOACCUMULATION OF HEAVY-METALS BY BENTHIC INVERTEBRATES AT THE ARKANSAS RIVER, COLORADO

A one-year biomonitoring study was conducted to determine the extent of metal contamination (Cd, Cu, and Zn) in a benthic community from the Arkansas River (CO), a subalpine stream impacted by discharges from historic mining operations. Elevated concentrations of metals in water were paralleled by higher concentrations in benthic organisms. Significant differences (p < 0.05) in metal concentrations in aufwuchs and benthic macroinvertebrates among upstream (reference) and downstream (impacted) stations were observed. Metal concentrations in aufwuchs and benthic invertebrates remained elevated at some downstream stations, despite decreases in water concentrations. Time of year and functional group contributed to the variation in metal bioaccumulation in benthic macroinvertebrates. Monitoring metal concentrations in aquatic macroinvertebrates was a better indicator of metal bioavailability in the Arkansas River than ambient (water) metal concentrations.