Dissolved organic matter dynamics in stream ecosystems

人类造成的最明显的环境变化之一是景观的改变。这通常涉及以牺牲农业和城市地区为代价减少森林覆盖。由于土地和水之间的联系发生了变化，土地利用的这些变化几乎不可避免地影响了地表水和地下水的质量和数量。对于这些景观中的河流来说，新的景观连接可以改变有机质（通常以溶解有机碳（DOC）为碳单位测量），这些有机质现在主要来自农作物、粪便和城市垃圾，而不是天然植被、土壤和湿地。改变景观和河流的新联系也改变了河流碳的化学成分，这可以改变我们河流的健康功能。在这个项目中，我将研究安大略省中南部五大湖盆地对比土地利用的河流流域DOC的质量和数量是如何变化的。这些数据将用于进一步研究物理（如水流）、化学（如营养物）和生物（如水流食物网）的土地利用变化如何改变DOC的加工和出口。在此过程中，我将测试农业和城市来源的DOC和营养素如何影响微生物生长，食物网组成和生态系统功能，如材料（叶凋落物）的腐烂，藻类的营养吸收和氮循环。最后，我将测试河流DOC对气候变化的反应，因为这些可能受到温暖天气和干旱时期的影响。这项研究将帮助我们了解人类来源的材料（农业肥料和生活垃圾）将如何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.