The impact of environmental change on dissolved organic matter cycling in boreal watersheds

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Dissolved organic matter (DOM) fuels the microbial activity that drives elemental cycles and represents the largest active pool of carbon in the aquatic environment. Climate and watershed models predict significant changes in DOM transport from boreal watersheds that will have large implications for freshwater and marine ecosystems. Streams are the primary location for elemental cycling within watersheds but are also the most impacted locality within watersheds. Land use trends are currently causing increases in the solar radiation and nutrients, such as nitrogen and phosphorus, reaching streams. Nutrients are known to impact how microorganisms and solar light process DOM in the aquatic environment yet the impact of elevated nutrient levels on stream DOM cycling remains poorly understood. The proposed research program will focus on three main questions: (1) How does the source and composition of boreal stream DOM vary among different boreal watershed types?; (2) What effect do elevated nutrient concentrations have on microbial and light-mediated processing of boreal stream DOM?; and (3) How can elevated nutrient concentrations impact composition and function of microbial communities in boreal streams?