Deep Water Microbialites in a Perennially Ice-covered Lake: a Key to Interpreting Ancient Microbialite Morphology

Grant #: NNX08AO19G
Senior Scientist: Dale Andersen

We will propose a robust, interdisciplinary scientific effort to investigate the benthic microbial ecosystem in Lake Joyce, a perennially ice-covered lake in the McMurdo Dry Valleys with the goal of further understanding factors that control the morphology of ancient microbialites. Understanding the early evolution of life depends on inferring triological properties from the remnants of fossilized microbial communities. Most of our understanding of microbialite formation comes from tropical or subtropical locations. We propose to add to our understanding of microbialite formation by investigating modern calcifying microbial communities in Lake Joyce, Antarctica. Previous work on uncalcified mats in Lake Hoare, Antarctica, demonstrates that microscale gradients in water chemistry are directly related to both mat morphology and metabolic activity. Previous laboratory experiments with filamentous cyanobacteria demonstrate that specific motility patterns create networks of ridges and peaks that have been observed in Lake Joyce. We will propose to develop a predictive understanding of what underlies both the development of the ridged and peaked morphology in microbial mats at extreme low temperature and irradiance and how organisms forming these structures interact with water chemistry to form intricate microbialites. While of interest in its own right, when combined with existing research on microbialite formation, this new data from an extreme environment will help set limits for the types of community and environmental conditions that are prerequisites to their formation. We will propose to fully characterize carbonate precipitation in the lake, specifically evaluating the roles of lake chemistry and microbial processes. We will produce the second characterization of benthic mats in MCM lakes, with a new focus on mats with significant morphological complexity. We will use these data to constrain the origins of mats with intricate topography, specifically evaluating the role microbial properties on the development of topography. We will place results into the context of other modern and ancient microbialites with a strong emphasis on identifying key structures that reflect microbial behaviors. Thus, results from this highly collaborative research effort will provide innovative and novel insights into MCM lacustrine processes and microbial ecology as well as the controls on morphology in microbialites of any age.