Long-term effects and recovery of streams from acid mine drainage and evaluation of toxic metal threshold ranges for macroinvertebrate community reassembly.

Monitoring of benthic invertebrates in streams receiving acidic metal-contaminated water over an 18-yr period revealed both degraded conditions and recovery along a network of downstream locations. Compared with reference streams, and over the course of clean-up remediation efforts below an abandoned open-pit sulfur mine in the central Sierra Nevada of California, improving water quality was accompanied by recovery of benthic communities at some sites. Years of high flow resulted in degraded biological status when acid mine drainage capture was incomplete and metal loading had increased with runoff.