MACROINVERTEBRATE AND FISH POPULATIONS OF 4 STREAMS RECEIVING HIGH-RATES OF HYDROGEN AND SULFATE ION DEPOSITION

We compared selected water quality parameters with macroinvertebrate a nd fish community dynamics among one episodically-acidified stream and three circumneutral streams on Laurel Hill in southwestern Pennsylvan ia over a four-year period. Water quality parameters associated with e pisodic acidification (pH, total alkalinity and total aluminum) were a nalyzed during high and low stream discharge. Acid episodes occurring during spring peak runoff periods in the poorly-buffered stream result ed in maximum depressions of pH (7.13 to 4.36) and total alkalinity (1 8 mgL(-1) to 2gL(-1)), and elevations in total aluminum (0 to 490 ugL( -1)) when compared with the circumneutral streams (pH 7.5 to 6.29); to tal alkalinity (25 mgL(-1) to 9 mgL(-1)); and total aluminum (10 to 18 0 ugL(-1)). Macroinvertebrate community parameters (number of taxa, di versity, and equitability were depressed in the acidified stream which was depauperate of Ephemeroptera and dominated by the plecopteran shr edders, Leuctra sp. and Amphinemura sp. Macroinvertebrate standing cro ps did not differ greatly among all streams. The Coefficient of Commun ity Loss indicated severe environmental degradation in the acidified s tream when compared with the reference streams. The brook trout popula tion, depressed in terms of standing crop and recruitment in the acidi fied stream, grew at the same rate as those of the circumneutral strea ms.