ELECTROCHEMICAL DETERMINATIONS OF KEY REDOX SPECIES ASSOCIATED WITH MICROBIAL ACTIVITY

Voltammetric microelectrodes have been successfully applied to a wide variety of marine and terrestrial systems to describe detailed redox chemistry associated with microbial activity over the past 12 years (Brendel and Luther, 1995 Luther et al., 2001; Taillefert et al., 2000; Druschel et al., 2004). The definition of microbial habitats, where competition for common electron donor/acceptors or nutrients/cofactors is a key to describing diversity in any environment, must be done on appropriate spatial and temporal scales. Once specific microbial habitats are described, the relationships between organisms and their surroundings may be more specifically addressed and studied. Collection of in situ, real time information, using Au-amalgam voltammetric electrodes, on a host of key redox species (including O₂, H₂O₂, Fe²⁺, Fe³⁺, FeS_(aq), Mn²⁺, H₂S, S_x^2-, S₈, S₂O₃^2-, S₄O₆^2-, HSO₃^-, and As³⁺) can delineate microbial habitats associated with specific groups of organisms on very small spatial scales (down to microns) and characterize changes in these species over time (down to seconds). We will review recent work in several localities reflecting different microbial habitats, including Yellowstone National Park, the Frassassi Cave system in Italy, Green Lake, NY, Lake Champlain sediments, and Butte, MT mine waters to discuss the importance of gathering detailed redox chemistry information applied to thinking about the role of microbes in geologic and environmental processes.