9319044 Green Lake Vanda is an ice-covered, permanently stratified lake. The water column, 69-meter deep, presents a wide range of geochemical and microbiological environments. The lake's 1200-year stratification history and its water column stability make it a model system for exploring the relationship between chemical processes and microbial diversity and activity. Of special interest is the relationship between successive reductive and oxidative zones and the microbial and chemical characteristics of those zones. Dr. Green and colleague plan the first simultaneous study of chemical and microbial community structure using a combination of measurements, including determinations of microbial biomass and diversity as estimated by microscopy and nucleic acid extraction and identification. Central to this work is the role played by manganese-reducing organisms in metal cycling in the Vanda water column. The capacity for microbially mediated manganese cycling will be assessed by determining the abundance of manganese reducers and the mechanisms involved in Mn reduction. In addition, a detailed study of metal transport mechanisms is planned along the 27-km course of the Onyx River, the lake's sole inflow. Determination of metal loadings and residences times in the lake will be made. ***
