Breakdown of plant litter in streams was studied as an example of a major ecological process subject to change through multiple stresses associated with mine drainage. Rates of litter breakdown were measured at 27 sites in streams of the Rocky Mountains of Colorado, USA. Eight of the sites were pristine, and 19 were affected to varying degrees by mine drainage. The pH, concentrations of dissolved zinc, and deposition rates of metal oxides were measured in each stream. Rates of litter breakdown were estimated from changes in mass of willow leaves in litterbags. Biomass of shredding invertebrates in litterbags was monitored at each site, as was microbial respiration on litter. Of the abiotic variables, increased concentrations of zinc and increased deposition rates of metal oxides were most closely related to decreased rates of litter breakdown. Biomass of shredding invertebrates was negatively related to concentration of dissolved zinc and deposition of metal oxides and was more closely related to breakdown rates than was microbial respiration. Microbial respiration was related negatively to deposition rates of metal oxides and positively to nutrient concentrations. Shredder biomass and microbial respiration together accounted for 76% of the variation in breakdown rates. Remediation schemes for streams affected by mine drainage should take into account the distinct ecological effects of the multiple stresses caused by mine drainage (pH, high concentrations of dissolved metals, deposition of metal oxides); remediation of a single stress is likely to be ineffective.


Biological Sciences


U.S. Geological Survey Toxic Substances Hydrology Program
University of Colorado
National Science Foundation (U.S.)


Funding for this research was provided by the U.S. Geological Survey Toxic Substances Hydrology Program, the University of Colorado, and a National Science Foundation dissertation improvement grant.

Keywords and Phrases

Decomposition; Litter; Mine Drainage; Rocky Mountains; United States; Invertebrata; Salix; Acidification; Colorado (USA); Litter Breakdown; Metal Toxicity; Microbial Respiration; Multiple Stresses; Shredding Invertebrates; Streams

International Standard Serial Number (ISSN)


Document Type

Article - Journal

Document Version

Final Version

File Type





© 2001 Ecological Society of America, All rights reserved.

Publication Date

01 Apr 2001

Included in

Biology Commons