Jennifer A. Roberts, David Graham, and William D. Picking, University of Kansas Rachel O'Brien, Allegheny College
Participation of bacteria in mineral weathering is now an accepted, even expected component of subsurface geochemistry. Microorganisms have been found at depths exceeding 3 kilometers and at temperatures approaching 100C, and there is growing evidence that the biochemical functions of these organisms may be the driving force behind many low temperature mineral-weathering reactions. The scientific community has only begun documenting microbial-catalyzed reactions, however, and many questions arise. Do the responsible organisms benefit from weathering reactions? How does mineral dissolution affect biodiversity in colonizing microbial communities? Such weathering reactions have likely been operative since the beginning of geologic time. Therefore, understanding such phenomena, and the associated organisms, not only provides an immediate picture of ambient weathering phenomena, but might also provide insights into microbial evolution and factors that control subsurface biodiversity. There are two goals for this work. First, we will investigate nutrient-driven and metal-inhibited microbial weathering of synthetic and natural silicate phases using native consortia from a from six distinct groundwater ecosystems (temperate hardwood forest, tropical forest, tropical clearcut grassland, temperate tallgrass prairie, boreal wetland, and a tropical wetland). The results of this work will demonstrate how trace concentrations of nutrients and metals in the solid phase influence microbial weathering reactions. Second, we will characterize microbial activity, community composition, and biodiversity in a select group of groundwater ecosystems. Following this characterization we will examine the microbial population succession that results from the introduction and weathering of nutrient- and metal-bearing silicates. Results from this project will lend insight into the influence of silicate-bound nutrients and metals on microbial weathering, and how mineral composition and weathering reactions impact the biodiversity of the surface colonizing microbial community for a variety of groundwater ecosystems. Our investigations will also elucidate how modern microbial weathering processes function, and in turn, may help identify key processes through geologic time.
