An evaluation of benthic invertebrate communities as an indicator of stream ecosystem health below active coat mines in the Elk River watershed Frenette, Jody L.
The objective of this research was to determine whether the benthic invertebrate community structure is impacted by coal mining within the Elk River Basin. Obvious changes in water quality below the coal mines included increased selenium, sulphate, nitrate and nitrite concentrations. Selenium concentration was the only water quality variable that showed a relatively strong negative correlation with changes in benthic community structure, while depth and predominant substrate were also strongly correlated. Benthic invertebrate tissue samples collected in 2006 and 2007 below Elkview and Coal Mountain Operations suggest that tissue selenium concentration can be within the range of lethal or sublethal toxic effects, therefore affecting community structure. However, benthic invertebrate communities assessed within Michel Creek were found to be within the natural variability as determined by the reference sites sampled, except for a decrease in sensitive species, Ephemeroptera. The abundance and proportion of EPT and Ephemeroptera significantly decreased below coal mining, while Dipterans, particularly Chironomidae, increased. Although the changes within benthic communities were subtle compared to the water quality changes, this does suggest an impact to the aquatic health. In addition, if decreasing Ephemeroptera was truly an effect of coal mining, number of EPT, % EPT, number of Ephemeroptera and % Ephemeroptera may be possible metrics useful for detecting coal mining impacts as suggested by Garcio-Criado et al. (1999).
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