Effects of Placer Mining on the Invertebrate Communities of Interior Alaska Streams

To determine the effect of placer mining on benthic macroinvertebrates we determined selected water quality characteristics and sampled benthic invertebrates in nine hydrologically similar and proximally located streams, ranging from unmined to heavily mined streams. Placer mining caused increased turbidity, and increased amounts of settleable solids, and suspended sediment (nonfilterable residues). Sediment from placer mining was associated with decreased density and biomass of invertebrates. In a stream where mining began in mid-August, Orthocladiini (Diptera: Chironomidae) and Chloroperlid stoneflies decreased in abundance while they were not decreased in a nearby unmined stream. Water mites seemed to be the organisms most affected by placer mining.