ACID ROCK DRAINAGE AND TROUT: A REVIEW

Historically, the allure of the mountains of the American West was largely extractive, for commodities including timber and precious metals. Pursuit of the latter commodity, and the resultant generation of widespread and persistent anthropogenic sources of acid rock drainage, left a significant water quality legacy within many streams draining these mountainous regions. As the primary aquatic vertebrate residing in these cold waters, trout are frequently utilized as indicator species for the severity and extent of the environmental impact of legacy mining.

At one extreme, acid rock drainage can yield elevated concentrations of toxic metals that are quickly lethal to trout. Importantly, the susceptibility of trout to acute metal toxicity has been observed to vary significantly both by metal, and by trout species. The toxicity of metals is frequently mitigated by the other dissolved constituents in natural waters. In addition, acid rock drainage can limit the productivity and persistence of a trout population through disruption at lower trophic levels (e.g. macroinvertebrates) at trace metal concentrations that are not acutely lethal to trout. This presentation will utilize recent field and laboratory studies to explore the diversity of pathways through which acid rock drainage can limit downstream trout populations.