Sk. Meegan et al., DETRITAL PROCESSING IN STREAMS EXPOSED TO ACIDIC PRECIPITATION IN THECENTRAL APPALACHIAN MOUNTAINS, Hydrobiologia, 339(1-3), 1996, pp. 101-110
Continuing high rates of acidic deposition in the eastern United State
s may lead to long-term effects on stream communities, because sensiti
ve catchments are continuing to lose anions and cations. We conducted
a two-year study of the effects of pH and associated water chemistry v
ariables on detrital processing in three streams with different bedroc
k geology in the Monongahela National Forest, West Virginia. We compar
ed leaf pack processing rates and macroinvertebrate colonization and m
icrobial biomass (ATP concentration) on the packs in the three streams
. Breakdown rates of red maple and white oak leaf packs were significa
ntly lower in the most acidic stream. The acidic stream also had signi
ficantly lower microbial and shredder biomass than two more circumneut
ral streams. Shredder composition differed among streams; large-partic
le detritivores dominated the shredder assemblages of the two circumne
utral streams, and smaller shredders dominated in the acidic stream. W
ithin streams, processing rates for three leaf species were not signif
icantly different between the two years of the study even though inver
tebrate and microbial communities were different in the two years. Thu
s, macroinvertebrate and microbial communities differed both among str
eams that differed in their capacity to buffer the effects of acidic p
recipitation and among years in the same stream; these differences in
biotic communities were not large enough to affect rates of leaf proce
ssing between the two years of the study, but they did significantly a
ffect processing rates between acidic and circumneutral streams.