INFLUENCE OF DIATOM DIVERSITY IN AN INDIANA STREAM IMPACTED BY ACID MINE DRAINAGE

Acid mine drainage (AMD) associated with the abandoned Green Valley coal mine site in West Terre Haute, IN, discharges into West Little Sugar Creek (WLSC), a nearby natural stream. The area has been impacted by AMD for nearly 55 years, denoting WLSC as one of Indiana’s most contaminated water systems. Despite various remedial efforts, AMD still discharges into WLSC, where pH drops to as low as 3. The acidic effluent and stream water contains elevated concentrations of SO₄, Fe, Al, and trace elements, many of which exceed state and federal surface water quality standards. Local aquatic life is adversely impacted by the high acidity and high concentrations of dissolved constituents. Downstream of the mines site, metal concentrations decrease and pH increases due to dilution from surface water runoff and groundwater discharge into the stream.

To assess the environmental impact of AMD on the ecology of the WLSC stream system, this study evaluates changes in diatom species upstream and downstream of the discharge zone. Diatoms were selected because of their abundance in most water systems, high diversification, and siliceous frustules, the latter of which is often preserved in sediment. Diatoms are known to be highly sensitive to environmental changes, such as toxic metal concentrations and acidity. We hypothesize that the low pH and highly toxic conditions of WLSC will decrease species diversification downstream. Specifically, we examine changes in riverine diatom communities downstream from the discharge site to determine how far downstream the influence of acid mine drainage persists and to establish a baseline for seasonal fluctuations to help evaluate the resilience of these communities.