Structural and functional responses of stream insects to copper pollution

Benthic invertebrate assemblages and leaf decomposition rates were usedto assess the effects of copper on community structure and function in EastProng Creek, VA. Copper concentrations ranged from 12–32 µgl^–1 at three downstream disturbed sites and 0.1–2.0µg l^–1 at an upstream reference site. Benthic samplingshowed reduced taxonomic richness and numbers of individuals at thedisturbed sites and leaf decomposition rates at the disturbed sites were1.4–2.7 times slower than at the upstream reference site. Partialrecovery of community structure occurred after a passive treatment systemreduced copper to levels below chronic effect concentrations. Post-treatmentbenthic sampling indicated a recovery in taxonomic richness in the threedisturbed sites. During the 6-week period of treatment, themacroinvertebrate community in the disturbed sites recovered to a similarcomposition to that found in the reference site. However, no significantdifference in leaf decomposition rate was observed, suggesting a residualeffect of copper on our measure of functional response. Our results indicatethat copper pollution significantly interrupts the action of shreddersprocessing leaf material in polluted streams.