Effects of gravel augmentation on invertebrate assemblage and biomass in the American River, CA

In recent years, restoration of Salmonid spawning habitat within California’s waterways has become a necessity.  Mass disturbances in rivers (e.g., channelization, dams, habitat loss) and their effects on target species have been of interest among ecologists.  However, less attention has been placed to the effects of these disturbances on benthic communities as they may alter habitat and food availability. A gravel augmentation project was conducted adjacent to Sailor Bar of the American River in Sacramento County, California.  To determine how restoration projects impact benthic macroinvertebrates, a study comparing invertebrate community structure in a restored gravel enhancement reach with an unrestored reach was performed.  The unrestored reach was dominated by highly tolerant taxa (e.g., Chironomidae; 22-30%), while the restored reach was dominated by sensitive taxa (e.g., Hydropsychidae, Baetidae; 52-60%).  Benthic invertebrate communities were characterized by filterers (20-59%)and gatherers(39-80%)in the restored reach and by gatherers(40-62%)] and scrapers(18-32%) in the unrestored reach. Additionally, the unrestored reach had higher family richness than the restored reach (13-16 vs 6-7). Results suggest that restoration efforts in the American River can influence benthic community structure and function.