Benthic invertebrate metals exposure, accumulation, and community-level effects downstream from a hard-rock mine site

This study quantitatively evaluated the relationships among As, Co, and Cu concentrations in exposure media (surface water, sediment, and aufwuchs), As, Co, and Cu concentrations in aquatic macroinvertebrates, and invertebrate community structure in a mine-affected stream. Concentrations of As, Co, and Cu were significantly elevated in both exposure media and invertebrate tissue downstream from the mine. Copper in invertebrates was significantly correlated only with Cu in aufwuchs, and Co in invertebrates was significantly correlated only with dissolved Co in water, suggesting different mechanisms of invertebrate accumulation for these two metals. The invertebrate community was severely affected downstream from the mine, with a loss of metals-sensitive species and reductions in both total biomass and number of species. Total abundance was not affected. Principal components analysis was performed on the invertebrate community data to develop a simplified description of community response to mine inputs. Based on this index, metal concentrations in invertebrates were poor predictors of community structure. Copper concentrations in water, combined with an estimate of invertebrate drift from clean tributaries, were statistically significant predictors of community structure.