Dissolved organic matter dynamics in stream ecosystems

人类活动引起的最明显的环境变化之一就是景观的改变。通常 这涉及到以牺牲农业和城市地区为代价减少森林覆盖。几乎不可避免地， 土地利用的这些变化影响了地表和地下沃茨的质量和数量， 土地和水之间的联系。对于这些景观中的河流，新的景观连接可以改变 有机物（通常以碳单位测量，如溶解有机碳（DOC））， 主要来自农作物、粪肥和城市废物，而不是自然植被、土壤和湿地。 与改变的景观和河流的新联系也改变了河流碳的化学性质， 改变我们河流的健康运行。在这个项目中，我将研究如何DOC的质量变化 和数量在河流流域的对比土地利用从五大湖盆地在中南部安大略。 这些数据将用于进一步研究土地利用的物理变化（例如，溪流）、化学 (e.g.,营养素），和生物（例如，流食物网）改变DOC的加工和出口。在这样做时，我 将测试农业和城市来源的DOC和营养物质如何影响微生物生长，食物网 组成和生态系统功能，如材料（落叶）的腐烂，藻类的营养吸收， 氮循环最后，我将测试河流DOC对气候变化的反应，因为这些可能是 受温暖天气和干旱的影响。这项研究将帮助我们了解人类来源的 农业肥料和生活垃圾等有害物质将影响水生系统的健康和完整性。

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.