SPATIAL VARIABILITY OF ECOLOGICAL AND WATER QUALITY IMPACTS OF ACID MINE DRAINAGE IN AN ALPINE WETLAND

Acid mine drainage (AMD) can adversely affect aquatic and semi-aquatic life in impacted areas, resulting in a loss of species diversity and abundance, as well as an interruption of the food chain. Bilger Run Wetland, located in the Allegheny Plateau of central Pennsylvania, was impacted by AMD due to extensive bituminous coal mining operations within the watershed. The wetland, 16 ha in area, is supplied water by a watershed of 518 ha covered primarily by forest, reclaimed mine land, and farm land.

In order to learn more about relationships between water quality and ecology at the site, we monitored pH and conductivity at 47 locations within a 9.5 ha portion of the wetland monthly for 12 months, in addition to observing vegetation, vertebrates and macroinvertebrates at these locations. Time-averaged pH and conductivity varied from 3.6 to 6.0 and 200 to 2160 uS/cm, respectively, within the wetland, representing a mix of dilute water, untreated AMD, and treated water entering the wetland from various sources. Despite direct inputs of untreated AMD and a relatively low spatially-averaged pH of 4.7, vegetative cover in the wetland was lush, albeit populated by acid-tolerant flora. However, macro-invertebrates observed throughout the wetland were limited to pollution-tolerant species, and no fish species were observed.

Preliminary bird observations prompted us to conduct bird point count surveys at a subset of locations within the wetland twice monthly the following year from May to August. A positive correlation was found between mean spatially-interpolated water pH in the observation areas and bird species richness, suggesting that acidic conditions may have an adverse affect on bird species richness in a wetland environment.