Assessment of mine drainage remediated streams using diatom assemblages and biofilm enzyme activities

Abstract

A legacy of pre-regulation coal mining in many areas has been acid mine drainage (metal-rich, low pH water). Today, numerous remediation strategies may be implemented, but there is little data on efficacy in restoring biological condition. Two alkaline doser projects in Ohio were assessed using diatom assemblages, and biofilm extracellular enzyme activities (EEA). In one stream, water quality steadily increased downstream of the doser; pH increased from 3.8 to 7.2 and Fe decreased from 107 to 0.42 mg l−1. Likewise, the periphyton biomass (chl a 7.15–12.77 mg m−2) increased and periphyton index scores (4–27) improved. As well, EEA data showed greater activity for phosphorus, nitrogen, and one carbon acquisition enzyme. For the other stream, the conductivity remained high (>720 μS cm−1) and pH and alkalinity decreased downstream. Biological data, including EEA, varied along the stream length with higher numbers in the middle reach, such as chlorophyll a (0.56 to 87.75 to 2.77 mg m−2), and index scores (7 to 29 to 11). The first remediation site showed positive results in chemistry, biological community and measures of ecosystem function. The second stream was highly variable in these parameters suggesting further AMD inputs are hampering recovery.