Photochemical and microbial processing of newly exposed carbon

This project will investigate the fate of dissolved organic matter (DOM) released in increasing amounts to Arctic surface waters through such disturbances as fire, thermokarst failure, and thawing of permafrost. The investigators hypothesize that newly available soil carbon will be labile to photochemical and microbial attack, and will enhance the degradation of resident DOM in the system resulting in poorer quality DOM exported to the ocean. They plan to develop a mechanistic understanding of these processes by: (A) Determining how fast photochemical reactions and microbial processing will alter resident DOM and the newly-released DOM in surface waters, and (B) Measuring the fate of DOM in surface waters, either as CO2 released to the atmosphere or as organic carbon altered and transported to coastal oceans. This would be accomplished with a series of laboratory experiments to determine rates of photodegradation and microbial processing of DOM from different sources, and a series of landscape comparisons and sampling transects to characterize DOM degradation in small basins and large rivers extending 250-300 km from the headwaters to the Arctic Ocean. By integrating this process-based research with ongoing projects studying the formation of thermokarst failures and the impacts of burning on plant and soil carbon allocation, the investigators will address questions such as whether carbon export from tundra to oceans will rise or fall, how reactive is that exported carbon, and what will be the ultimate impact of impending disturbances, including climate change, on the net carbon balance of the Arctic and its interaction with the global carbon cycle. The investigators will work with several established programs at UNC and UM to (1) recruit women and minority student participation and research in this project specifically from Historically Black Colleges, (2) participate in a workshop on mentoring strategies for minorities, and (3) develop additional outreach activities, including talks to middle and high schools by the PIs, graduate, and undergraduate students. Presentation of data will coordinate with NSIDC and Arctic LTER data management.