Understanding the Effects of Climate Change on Carbon Fate in Headwater Lakes

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The millions of lakes in Canada are essential to our identity. We regard our freshwater as our most important natural resource. To protect this resource, we need to better understand how lakes function and how catchments drive the fate of carbon (essential to all life, is a greenhouse gas as carbon dioxide and methane, and provides colour to water) in lakes in order to make predictions about how climate change will affect our lakes. The forested landscapes around lakes are critical to water supplies since they provide the majority of drinking water in Canada. A key factor to safe drinking water supplies is managing dissolved organic carbon (the substances that give natural water their colour) in lakes in order to make it treatable without elevated levels disinfection by-products. The effects of climate change on the export of water and carbon from catchments to headwater lakes and the fate of carbon in those lakes is poorly understood.Small lakes are good model ecosystems because they are large enough to contain a full food web, from microbes to fish, come in a variety of sizes and can have a wide range of influences from their catchments. Small lakes are also very good sentinels of change. The Experimental Lakes Area and Dorset Environmental Science Centre offer a rare opportunity to study the role catchments play in driving colour, risk of anoxia, treatability of drinking water, and the fate of carbon in lakes across a climatic gradient. Further, combining their respective decades of research and monitoring with novel analyses provides a unique and exciting approach. There is clear evidence that lakes are changing due to climate change, for example, longer periods of summer stratification allow bottom waters to become anoxic more often and seasonal changes in catchment loading of carbon and nutrients to lakes affects their fate.To date, little work has combined catchment characteristics (such as landcover type, slope, shoreline shape factor and catchment to lake ratio) with dissolved organic carbon quality (such as different types of fluorescence, size fractionation and disinfection by-product formation) to understand how the fates of different types of organic carbon in headwater lakes. The proposed research will make the first big steps in this direction. Outcomes of this research will be used to identify types of lakes that are better suited to drinking water provision. This is critically important for northern communities that have faced long-term problems with safe drinking water. Ultimately, the development of models to predict climate change effects on the fate of carbon in lakes are needed in order to protect the health of these lakes and the services the provide us.