Semester

Fall

Date of Graduation

2010

Document Type

Thesis

Degree Type

MS

College

Davis College of Agriculture, Natural Resources and Design

Department

Wildlife and Fisheries Resources

Committee Chair

J. Todd Petty.

Abstract

Acid precipitation and acid mine drainage have dramatically altered chemical conditions and biological assemblages in streams throughout the central Appalachians. Effects of acidification on functional stream processes such as organic matter decomposition, however, remain poorly understood. The objectives of this study were to: (1) quantify differences in organic matter decomposition among reference streams, streams impacted by acid precipitation, and streams impacted by acid mine drainage; and (2) determine if lowered decomposition rates are the result of reduced microbial activity or altered invertebrate shredder assemblages or both. I quantified water chemistry, organic matter decomposition, microbial activity, and macroinvertebrate community structure in 15 headwater streams in the central Appalachian ecoregion (5 circumneutral reference, 5 acid mine drainage, and 5 acid precipitation). Decomposition rates were quantified from leaf packs deployed for a period of 120 days over three seasons. Water chemistry was sampled in conjunction with decomposition trials. Benthic invertebrate communities were sampled in spring and fall. Microbial activity was measured as total microbial community respiration and ergosterol content. Acid mine drainage resulted in dramatically reduced shredder assemblages, reduced microbial activity and reduced overall organic matter decomposition. Acid precipitation resulted in altered shredder assemblages, reduced microbial respiration and diminished organic matter decomposition, but not as severely as seen in acid mine drainage streams. Overall, decomposition rates were more strongly correlated with microbial respiration and ergosterol concentration than shredder community composition. However, shifts in shredder assemblages, including the loss of acid sensitive voracious shredders, such as Lepidosotoma, Limnephilidae, Petronarcys, Gammarus, and Decopoda, also is likely responsible for the reduction in organic matter processing ability in acid impacted streams. Our results provide further evidence that restoration of acidic headwater Appalachian streams is needed in order to effectively manage conditions in larger aquatic ecosystems downstream.

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