Phycomicrobial Ecology of Acid Mine Drainage in the Piedmont of Virginia

摘要

Acid mine drainage encompasses 18 km~2 of Louisa County, Virginia. Heavy metal laden acidic leachate flows from abandoned mines along the Piedmont's Gold-Pyrite Belt. The oxidation of pyrite, sphalerite, chalcopyrite and other sulfide minerals that are disseminated throughout the mine tailings release H_2SO_4, Fe, Cu, Zn, Ni, Cd, As, Pb and other heavy metals into the Contrary Creek watershed and beyond, into Lake Anna. Downstream of these abandoned pyrite mines, high levels of acidity and heavy metals have made this a severely stressed environment incapable of supporting a healthy creek ecosystem. In an effort to assess in-situ, bioaccumulatory remediation of acid mine drainage by phyco-microbial mats, surveys have been conducted for 11 months in Contrary Creek; several extremophiles that are tolerant of acid mine systems have been found. Twelve to thirteen genera of algae and a few cocci and bacilli have been identified in surface waters. Predominant genera include Ulothrix. Pinnularia and Oscillatoria. Preliminary results demonstrate that the phycomicrobial communities found in this acid mine system maintain density and species diversity independent of pH and heavy metal fluctuations. These extremophiles also demonstrate high potential for heavy metal sorption. Phyco-microbial mats bioaccumulate 60-70% more heavy metals than concentrations found in surface waters and the creek. To date, remediatory attempts to restore Contrary Creek have not been successful. Our results suggest that the extremophile ecology found in this system will facilitate the remediation process of other, similar acid mine affected ecosystems.