Structural and functional measures of macroinvertebrate recovery along an acid mine drainage gradient

Acid mine drainage impacts many streams in the Appalachian coal-mining region, altering both the structure (diversity, biomass) and functional properties (litter degradation, primary production) of stream ecosystems.  To assess the sensitivity and nature of structural versus functional measures of biological recovery, we monitored macroinvertebrate communities at seven sites (up to 11 miles) downstream an alkaline doser installed in 2003.  Annual monitoring revealed year to year variation in macroinvertebrate diversity and abundance, particularly in the first few miles downstream from the doser. Further downstream, community composition became more consistent.  In autumn 2008, leaf litter conditioning (measured as microbial respiration), breakdown rates, and shredding macroinvertebrates showed similar patterns of recovery.  We conclude that both structural and functional measures of biological quality are useful monitoring tools for tracking recovery in acid mine streams treated with alkaline addition.