The acid mine drainage environment: Impact of physico-chemical changes associated with remediation on microbial communities

Acid mine drainage is an environmental hazard that affects aquatic ecosystems around the world. AMD impacted sites are characterized by elevated concentrations of iron, sulfate and soluble toxic metals. Although extreme environments, like those impacted by AMD, adversely affect the macrofauna, they harbor acidophilic microbial communities. In this study, we generated baseline data about physico-chemical characteristics of AMD sites and examined how chemical remediation affects these properties. The impacts on the microbial community and ecological implications were examined. To fulfill these objectives, water and sediment samples were collected on several dates from three locations along an AMD impacted stream (a tributary of Huff Run, near Mineral City, OH, USA). pH prior to remediation increased in a downstream direction from, 3.0-3.5, but was almost uniform during remediation with a pH of 3.5 at all sites. Turbidity before remediation ranged between 0.42 to 0.50 NTU; it increased uniformly during remediation (18.0-20.2 NTU). Conductivity decreased during the process. Microbial communities were examined based on cultivation, microscopy, and DNA extraction followed by amplification of a fragment of the 16S rRNA genes and analysis via denaturing gradient gel electrophoresis. There were specific physico-chemical changes associated with remediation that may impact microbial community structure and function.