This award is for a postdoctoral fellowship. The investigator will characterize the carbon cycling and microbial diversity in the subglacial lake environment at Blood Falls in the McMurdo Dry Valleys of Antarctica. By using new isotopic biomarker techniques the applicant will explore microbial metabolism in this marine incursion that has likely been isolated from organic inputs since the Pliocene. Her work has implications for understanding the role of such closed systems in historical carbon dioxide cycling on Earth as well as for our understanding of similar systems on other planets.