BIOGEOCHEMICAL ANALYSIS OF MICROBIAL COMMUNITY STRUCTURE IN ALPINE PEEKABOO GULCH, COLORADO

This project expands a 2005 preliminary examination of factors that influence non-anthropogenic acid rock drainage in the Peekaboo Gulch drainage basin (Sawatch Range, Colorado). At this site, natural acid rock drainage outflows from acidic springs (pH=2.6) on Red Mountain. The acid drainage converges with South Fork Lake Creek (pH ≥ 7.0, prior to convergence) two miles down gradient. Detailed microbial and chemical analyses were conducted on water, biofilm, and sediment samples collected during the 2007 post spring run-off conditions. These analyses included the use of DGGE, PLFA, and RNA techniques to further identify and characterize the members of the microbial community and their structure within the pH gradient and immediate surrounding areas. Filtrate samples were collected from acid springs, iron bogs, acid streams, and along the mixing zone at the confluence of South Fork Lake Creek with Peekaboo Creek. This sampling routine is a compliment of the BioTrap® method utilized previously, and results are compared to BioTraps® that were left over-winter. Microbial genera identified from the preliminary study include Gallionella, Pseudomonas, and Actinobacter, differing from the bacterial genera typically reported in the literature in conjunction with acid rock drainage. The presence of Gallionella and the iron- and aluminum-rich, amorphous, colloidal precipitates dominating the system suggests a biocolloidal sediment accumulation process. An emphasis during this current investigation is the comparison between microbial communities present in the aluminum-rich water and sediments versus the iron-rich environments. Toxic levels of metals are present in the drainage and appear to work in conjunction with colloidal precipitates to affect aquatic life. In summary, this project revisits a site that has demonstrated unique and previously undescribed geomicrobiological activity associated with natural acid rock drainage in an alpine system, and provides additional biogeochemical information regarding local metal transformation.