Dissolved organic matter dynamics in stream ecosystems

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One of the most obvious environmental changes caused by humans is the alteration of the landscape. Usually*this involves the reduction of forested cover at the expense of agricultural and urban areas. Almost inevitably,*these changes in land use affect the quality and quantity of surface and subsurface waters because of altered*connections between the land and water. For rivers in these landscapes, new landscape connections can modify*organic matter (generally measured in carbon units as dissolved organic carbon, DOC) which now originates*primarily from agricultural crops, manure and urban waste instead of natural vegetation, soils and wetlands.*Novel linkages with modified landscape and rivers also change the chemistry of river carbon, which can*change the healthy functioning of our rivers. In this project, I will examine how the DOC changes in quality*and quantity in river watersheds of contrasting land use from the Great Lakes Basin in South-central Ontario.*These data will be used to further examine how land use alterations of physical (e.g., streamflow), chemical*(e.g., nutrients), and biological (e.g., stream foodwebs) alter the processing and export of DOC. In doing so, I*will test how agriculturally and urban-derived DOC and nutrients affects microbial growth, food web*composition, and ecosystem function such as the decay of materials (leaf-litter), nutrient uptake by algae and*nitrogen recycling. Finally, I will test for river DOC responses to climate change because these might be*affected by periods of warm weather and drought. This research will help us understand how human-derived*materials (agricultural fertilizers and residential waste) will affect the health and integrity of aquatic systems.