The influence of water quality on macroinvertebrate community responses to copper in outdoor experimental streams

Abstract

Experiments were conducted in artificial streams to examine the influence of water quality on macroinvertebrate community responses to copper (Cu). Macroinvertebrate communities were established on substratum-filled trays placed in the Clinch River and transferred to two artificial stream systems (New River and Clinch River streams) receiving water from different sources. Alkalinity and hardness in Clinch River (CR) streams were ∼2–3 times greater than in New River (NR) streams. Results of ANCOVA indicated that effects of Cu were greater in NR than in CR streams. After 4 days, total macroinvertebrate abundance was reduced by 32% in NR streams at 6 μg Cu/l but only by 25% in CR streams at 15 μg Cu/l. After 10 days, Tanytarsini chironomids, the dominant and most sensitive organisms collected, were eliminated from NR streams at 13 μg Cu/l but reduced by only 35% in CR streams at similar Cu levels. Results of canonical discriminant analysis also revealed greater impact of Cu in NR streams. After 10 days, macroinvertebrate communities in NR streams at 9 μg Cu/l were similar to those in CR streams at 24 μg Cu/l. Responses to Cu in both experimental streams and at impacted field sites were highly variable among taxa. Orthocladiini chironomids and net-spinning caddisflies were quite tolerant of Cu in experimental streams and were the only groups that recovered in the field. Our results demonstrate the importance of accounting for both water quality and composition of the resident fauna for establishing site-specific water quality criteria.