Structural and Functional Characteristics of Mining-impacted Reconstructed Streams

The Clean Water Act [section 404; stream mitigation rule] mandates that mining operations permitted by the U.S. Army Corps of Engineers (COE) to impact streams by valley fill or other activities must employ compensatory mitigation (Register April 10, 2008). Reconstructed streams are one means of mitigation and are meant to replace ecosystem structure and function lost due to impacts. With the goal of restoring ecosystem processes and patterns in these headwater streams, reconstruction efforts can serve as an important environmental protection measure. Additionally, in 2012 EPA released A Function-Based Framework for Stream Assessments and Restoration Projects, a document aimed at those constructing and assessing restorations, which states that it would benefit “from review, comments, and example experiences and applications” (Harman et al. 2012). The research we present in this report is addressing these needs by directly measuring specific ecosystem functions of reconstructed streams as mitigation efforts on coal mine sites in southwestern Virginia, and can contribute to the knowledge of stream restoration practices and assessment. Organic matter (OM), primarily as leaf litter and detrital input, serves as an essential energy source and habitat for benthic macroinvertebrates within headwater and larger stream ecosystems. Alteration of the sources, production rates, or processing rates of OM due to disturbance could have cascading effects throughout these ecosystems. As a result, we see the assessment of OM dynamics as important when characterizing and evaluating the overall functional condition of streams, and when identifying restoration practices that improve stream functions. To address these needs we have measured litterfall input, leaf breakdown, and periphyton biomass accrual for eight low-order mining-impacted reconstructed streams, and evaluated them via comparison to four minimally impacted reference streams. Relationships of these functional measures with physical, chemical, and biological structural measures are also being investigated.