Heavy metals are highly toxic in the environment and their presence in sediments of Lake Coeur d'Alene (LCdA) in Idaho is mainly the result of historical mining in the mountains upstream. The objectives of this project are to 1) characterize the diversity of microorganisms in LCdA sediments using modern molecular biology techniques, 2) quantify the role of individual members of the microbial community in biogeochemical cycling of metals (Cu, Pb, and Zn), and 3) develop a dynamic numeric biogeochemical model of heavy metal cycling in sediment systems, calibrated to the unique environments of LCdA. These objectives will be met while testing the following overall hypothesis: A complex and dynamic community of phylogenetically distinct and previously uncharacterized microorganisms is present in the historically metal-contaminated sediments of Lake Coeur d'Alene. In response to a toxic metal stress, metal-tolerant species will dominate metal-sensitive species present in the sediments, with temporal and spatial microbial distribution and diversity dependant on the metal type and concentration. Dynamic biogeochemical models that incorporate chemical transport and reaction with novel microbial stress/response relationships and community dynamics can be used to 1) integrate complex microbial and geochemical observations across spatial and temporal scales, and 2) better predict broad community level response and influence on toxic metal cycling. Intellectual merit of the proposed activity: This project will significantly improve the quantitative understanding of interaction and response of a sediment microbial community subjected to severe heavy metal stress. Project objectives will be achieved by sampling LCdA sediments and identifying microbial diversity based on both 16S rDNA and rpoB gene sequences. These molecular techniques greatly facilitate the study of microbes in their natural environments and will provide a rational platform to base observations of community response to toxic metal additions. Shifts in microbial populations after being subjected to metal-stress will be quantified using terminal-restriction fragment length polymorphism (T-RFLP). Focused laboratory studies will be used to quantify the effects of toxic metals on microbial growth and inhibition for incorporation into the predictive model. The modeling effort will integrate for the first time to our knowledge, syntrophic consortium biotransformation dynamics, dose-dependent inhibition, and spatial and temporal dynamics of redox front formation under a diffusive transport regime. Broader impacts resulting from the proposed activity: While the research is focused on microbial communities in historically metal contaminated LCdA sediment, with increased industrialization worldwide, interactions of the environment and human contaminants have become more important issues, scientifically and socially, to the U.S. and internationally. The project integrates research mentoring and training of graduates, postdoctoral associate, and a research faculty. A supplemental grant for research experiences for undergraduates will be used to integrate undergraduate students into the research. The results will be published in a number of quality peer reviewed journal articles and will be conveyed to the public through presentations at local regulatory and public meetings, and at national and international conferences. An internet web site written for both scientists and non-technical readers will be developed. When complete, this research will significantly expand the fundamental and quantitative understanding of key biogeochemical processes for metals. The project has the potential to suggest fundamental improvements in metals-bioremediation technologies, since results will be broadly applicable in supporting innovative biological strategies to reduce human health risks and environmental damage from metal contaminated sites
