The impact of environmental change on dissolved organic matter cycling in boreal watersheds

溶解有机物(DOM)为推动元素循环的微生物活动提供燃料，是水环境中最大的活性碳库。气候和流域模型预测，北部流域的DOM迁移将发生重大变化，这将对淡水和海洋生态系统产生重大影响。溪流是流域内元素循环的主要地点，但也是流域内受影响最大的地点。土地利用趋势目前正在导致到达溪流的太阳辐射和营养物质(如氮和磷)的增加。众所周知，营养物质会影响微生物和太阳光在水环境中处理DOM的方式，但营养水平升高对溪流DOM循环的影响仍然知之甚少。拟议的研究计划将集中在三个主要问题上：(1)北方河流DOM的来源和组成在不同的北方流域类型之间是如何变化的？(2)提高营养浓度对北方河流DOM的微生物和光中介处理有什么影响？(3)提高营养浓度如何影响北方河流中微生物群落的组成和功能？

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?