EFFECTS OF ACID-MINE DRAINAGE ON THE CHEMICAL AND BIOLOGICAL CHARACTER OF AN ALKALINE HEADWATER STREAM

Distribution of metals in water and sediments, as well as spatial alteration in the benthic macroinvertebrate and fish assemblages, was assessed in an alkaline headwater stream in eastern Kentucky receiving runoff from an abandoned surface mine. Concentrations of aluminum, copper, iron, manganese, and zinc generally increased 2 to 3 orders of magnitude in the receiving water immediately below where the mine runoff entered the creek. Metals in the water column were transported downstream largely in association with suspended particulates and declined in concentration progressively in a linear fashion commensurate to distance below the mine drainage outfall. In contrast, metal enrichment of sediments occurred spatially in a non-incremental pattern and varied among locations in conjunction with sitespecific changes in concentration levels of sediment organic matter. Benthic macroinvertebrate and fish fauna were eliminated for a distance of 0.3 km below the outfall, presumably owing to the presence of high levels of dissolved metals and low pH. Recovery of stream benthos occurred 1.0-2.0 km further downstream and was characterized by numerical dominance of collector-gatherer trophic groups consisting primarily of midge larvae (Chironomidae: Orthocladiini). Fish fauna in downstream reaches consisted exclusively of creek chubs (Semotilus atromaculatus) and stoneroller minnows (Campostoma anomalum). Metal levels in water and sediments remained elevated in regions of biological recovery and, as a consequence, downstream communities were comprised predominantly of metal tolerant taxa. © 1990 Springer-Verlag New York Inc.