Title
Changes in the Benthic Community of Lake Creek, MT, Resulting From Mine Tailings Contamination
Abstract
The benthos of Lake Creek, Lincoln County, Montana were sampled in 1984-85 to determine the effects of a 2.5 years old tailings impoundment located adjacent to the stream. Sampling results were compared spatially in the 1984-85 data set, and temporally with a baseline data set collected three years prior to installation of the impoundment. Lack of replication in the baseline sampling design precluded the use of two-way ANOVA for analysis of temporal changes. Therefore temporal comparisons were made on the basis of changes downstream of the impoundment relative to changes upstream, as measured over time. Spatial comparisons upstream and downstream were made by one-way ANOVA.
Determination of the effects of the tailings impoundment was confounded by a tailings spill that directly contaminated the downstream stations. The spill was assumed to have had a much larger biological effect that did the tailings impoundment itself. Simuliidae and Rhithrogena spp. increased in abundance after the spill, the former as an opportunist, the latter was a coincidental benefactor since it was in the adult stage during the spill.
The before and after data sets were collected with different sampling gear and had unequal replicate samples within plots. The gradient effect of Bull Lake on Lake Creek was also a concern. These concerns were minimized by utilizing a methodology that analyzed the change in the relationship between control and impact areas over time.
Of 16 taxa analyzed, 10 decreased, two increased, and four showed no significant change in abundance in the impact area relative to the control from 1977-78 to 1984-85. Spatial comparisons above and below the impoundment in 1984-85 showed eight taxa significantly more abundant in the upstream area, five with comparable abundances, and three with greater abundances downstream.
Start Date
20-4-1990 1:00 PM
End Date
20-4-1990 3:00 PM
Document Type
Poster
Changes in the Benthic Community of Lake Creek, MT, Resulting From Mine Tailings Contamination
The benthos of Lake Creek, Lincoln County, Montana were sampled in 1984-85 to determine the effects of a 2.5 years old tailings impoundment located adjacent to the stream. Sampling results were compared spatially in the 1984-85 data set, and temporally with a baseline data set collected three years prior to installation of the impoundment. Lack of replication in the baseline sampling design precluded the use of two-way ANOVA for analysis of temporal changes. Therefore temporal comparisons were made on the basis of changes downstream of the impoundment relative to changes upstream, as measured over time. Spatial comparisons upstream and downstream were made by one-way ANOVA.
Determination of the effects of the tailings impoundment was confounded by a tailings spill that directly contaminated the downstream stations. The spill was assumed to have had a much larger biological effect that did the tailings impoundment itself. Simuliidae and Rhithrogena spp. increased in abundance after the spill, the former as an opportunist, the latter was a coincidental benefactor since it was in the adult stage during the spill.
The before and after data sets were collected with different sampling gear and had unequal replicate samples within plots. The gradient effect of Bull Lake on Lake Creek was also a concern. These concerns were minimized by utilizing a methodology that analyzed the change in the relationship between control and impact areas over time.
Of 16 taxa analyzed, 10 decreased, two increased, and four showed no significant change in abundance in the impact area relative to the control from 1977-78 to 1984-85. Spatial comparisons above and below the impoundment in 1984-85 showed eight taxa significantly more abundant in the upstream area, five with comparable abundances, and three with greater abundances downstream.