Macroinvertebrate community assemblages in streams of interior Alaska following placer mining

Alluvial gold mining, or placer mining, represents a major disturbance to stream ecosystems in interior Alaska. This process typically involves re-routing the stream to one side of the valley while the gravels are removed across the floodplain for processing. The stream is then re-directed back into a reclaimed new channel after mining has ceased in that section of stream. Macroinvertebrate colonization of reclaimed stream reaches is necessary for benthic community recovery following mining. Macroinvertebrate community assemblages at 36 sites on six streams in interior Alaska were examined. Sites with different mining histories were compared to control sites. TWINSPAN classification and ordination of sites using macroinvertebrate abundance indicated a greater similarity of sites within watersheds than between watersheds even though each watershed had a history of mining including recently mined sites. Significant differences were found for total invertebrate abundance, percentage dominant taxon and mean total biomass of macroinvertebrates between control sites and sites that were recently mined (less than or equal to10 years) and sites mined 1-50 years ago. Total macroinvertebrate abundance and biomass was lower and taxon dominance higher in both groups of sites with a history of mining. No significant difference in these or other measures was found for sites where mining occurred upstream. There was also no significant relationship between time since mining and the biotic measures used to summarize macroinvertebrate community structure. Although taxon richness recovered rapidly, no individual taxon was found to be a specific indicator of macroinvertebrate recovery since mining. Copyright (C) 2004 John Wiley Sons, Ltd.