DISSERTATION RESEARCH: Metabolic Resource Partitioning: Scaling Microbial Physiology from Individual Activity to Ecosystem Function

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Human impacts have altered the movement of resources within and across landscapes. Resources drive population dynamics, mediate ecological interactions, and are the currency governing elemental cycles such as the carbon cycle. For the most part, these cycles are controlled by microorgranisms. This project focuses on the physiology and diversity of aquatic microorganisms that use terrestrially-derived dissolved organic carbon, which over the past 30 years has been increasing in concentration in lakes and streams, causing them to turn brown. Not only is this "browning" unpleasant to look at, it represents a major change in the function of critically important earth ecosystems.The overarching goals of this research project are to link the diversity, physiology, and metabolic capacity of microorganisms to resource transformations in the environment. These goals will be addressed by focusing on resource specialization within communities, the abundance and activity of microbial specialists, and how they affect ecosystem functions. The proposed research project will achieve these goals by linking the diversity and physiology of specialized microorganisms to ecosystem functioning, specifically the carbon cycle. To accomplish this, the project will address the following questions: 1) How does variation in microbial metabolic activity influence the transformation rate and the fate of resources? 2) Do microbial diversity and metabolic activity provide insight into resource specialization and the transformation of resources? The project will use a combination of isotope-labeled resource tracking and single-cell approaches to understanding microbial metabolic activity and diversity. These techniques provide increased ability to track resources, such as terrestrially dissolved organic carbon, and to understand the physiology and diversity of specialized microorganisms. As such, the proposed project addresses how microbial activity, physiology, and diversity relate to ecosystem functions and the fate of resources.