Grant: Discovery Grants Program - Individual

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? The proposed research will be conducted using three pairs of boreal streams in Newfoundland, representing a gradient of nutrient enrichment. Use of Newfoundland streams will allow for the assessment of impacts typical of other Canadian boreal watersheds such as sewage, agricultural and forestry practices. Unlike many other populated Canadian boreal regions, it will be possible to establish control streams in proximity to impacted streams due to the small basin size and lack of nitrogen deposition characteristic of Newfoundland watersheds. In addition to the characterization of the study streams, field and laboratory experiments will be used to assess the combined influence of nutrients and light-mediated processes on DOM cycling in boreal streams. This research will provide needed information critical to government planners, industry, environmentalists and scientists interested in preservation and management as well as study of water resources.