Stream ecosystem response to mitigative limestone treatment in acid-impaired, Central Appalachian streams

We quantified water chemistry, primary production, and benthic macroinvertebrate and fish community structure in 20 Central Appalachian streams: 4 acidic streams, 8 naturally circumneutral streams, and 8 historically acidic streams treated annually with limestone sand over varying lengths of time. The objective was to determine the extent of chemical and biological recovery and temporal trends in the recovery process of limestone treated streams compared to circumneutral reference conditions in Central Appalachia. Results indicate that the application of limestone sand to acidic streams is effective in fully and immediately recovering some of the chemical and biological characteristics of naturally functioning stream ecosystems such as pH, alkalinity, calcium, Ca:H ratios, trout densities and trout yoy densities. However, recovery of many characteristics is strongly dependent upon spatial proximity to treatment, and still others are never fully recovered. Limestone treatment does not restore several major ions and nutrients (K+, Mg2+, Na2+, NO3-) or macroinvertebrate taxa richness, biomass, number of acid sensitive macroinvertebrate taxa and fish biomass nor reduce aluminum levels to circumneutral reference conditions. The degree of recovery in macroinvertebrate density, percent acid tolerant and acid sensitive taxa biomass in treated streams depended upon the distance to the upstream treatment location and the degree of recovery in fish species richness depended upon basin area. Full recovery of acid impaired streams will most likely require treatment at the watershed scale including multiple mainstem treatment locations and treating streams as a regional network