Effects of Acid Mine Drainage on a Headwater Stream Ecosystem in Colorado

Abstract

The ecological effects of acid mine drainage were investigated during the summer of 1993 on St. Kevin Gulch, a headwater stream near Leadville, Colorado. The stream currently receives acidic water from an abandoned mine. The pH downstream of the mine is between 3.5 and 4.5, and several metals exceed concentrations toxic to aquatic organisms. Zinc is present at especially high concentrations (1 to 10 mg/L) Furthermore, the stream bottom is covered with a thick layer of iron hydroxide precipitates. Effects on stream biota have been dramatic. Aquatic flora in the affected reach is limited to a green filamentous alga, Ulothrix subtilissima. Macroinvertebrate densities are significantly lower in the affected reach (mean= 99 indiv/m 2; SD= 88 indiv/M 2) compared to an upstream (pristine) reference reach (mean= 1,735 indiv/m 2; SD= 652 indiv/M 2). Functional processes were also studied in the stream. Net primary production (NPP) was measured during midday with recirculating chambers. Production was significantly lower in the affected reach (mean NPP 13.3 MgO 2 hr-1 m-2; SD= 87 MgO 2 hr-1 m-2) than the upstream reference reach (NPP= 64.1 MgO 2 hr-1 m-2; SD= 27.7 MgO 2 hr-1 m-2). Decomposition, measured with litter bags, was also lower in the affected reach than the upstream site. In 1994, St. Kevin Gulch is scheduled to undergo remediation that will treat the acidic water from the mine. Further studies on this stream will provide information on the recovery processes in lotic ecosystems

Meeting Name

Society of Environmental Toxicology and Chemistry 15th annual meeting

Department(s)

Biological Sciences

Document Type

Conference proceedings

Document Version

Citation

File Type

text

Language(s)

English

Publication Date

1994

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