Acid mine drainage (AMD) is prevalent worldwide and is one of the most common consequences of mining that affects freshwater streams. Yet, techniques to mitigate AMD remain difficult to assess and may respond over very long time periods after the restoration is completed. Affected streams are considered lifeless, have low pH, high concentrations of dissolved metals, and substrata coated with precipitates. Efforts which monitor the recovery of biota are essential to understand the effectiveness of restoration techniques.
Clinton County, located in northeastern Pennsylvania, is rich with natural resources that have been historically extracted and have now left behind streams impaired by AMD. Intensive mining in this area occurred in the early 1900s to the 1970s and have affected class A trout streams to an impaired condition leaving them with poor species richness and low abundance of fish or invertebrates. Remediation efforts in 2017 have focused on a re-mining and source abatement project to collect discharge and integrate basic lime materials with remaining mine spoils to offset acidic discharges. To assess this new effort, agency and university officials have collected seasonal biotic inventories at sites located above and below the AMD source and remediation location over several years. We collected invertebrates at Cooks Run, Rock and Camp Run using composite d-frame kick net samples and compared this to other biotic metrics including historic invertebrate and fish populations to assess the response of the stream biota to the remediation effort.
Results/Conclusions
Benthic invertebrates were collected, sorted, and identified to genus level. Biological indices were calculated to determine stream health and to see if there was an improvement from the re-mining and lime addition remediation efforts. Invertebrate species richness, diversity, and abundance were reduced in streams receiving AMD relative to unaffected upstream locations. Communities at sites affected by AMD were dominated by acid tolerant species such as chironomids, beetles, and true bugs, but had little to no sensitive species such as mayflies or caddisflies. Since 2017, our data indicate that these new re-mining efforts have slightly improved water quality, brook trout biomass, and benthic invertebrates but it appears more time is needed to understand the biotic response. Continuation of water quality analysis and biological fish and invertebrates sampling is suggested in order to understand the success of re-mining/source abatement of AMD.