CAREER: Potential for the Recovery of Biogeochemical Function in Degraded Stream Ecosystems

越来越多的研究表明，未受干扰的河流生态系统在改变流域氮(N)损失的形式、时间和幅度方面具有重要作用。不太清楚的是，在流域退化期间，这种能力是否以及在多大程度上减少了。艾米丽·伯恩哈特正在研究城市溪流中关键的生物地球化学功能(活性氮的去除和群落新陈代谢)是否以及如何受到影响，以及这些溪流是否有能力通过1)通过未经修改的景观进行的纵向运输(自然恢复)或2)广泛的河道重构恢复努力(人工解决方案)来恢复这些功能。伯恩哈特将在实验中测试城市溪流中氮的去除速度是否受到碳的强烈限制。这很可能是因为在城市分水岭常见的频繁暴雨中，微生物活动所需的有机物丢失了。最终，这项研究将增加我们对河流氮素循环的机理的理解，并将为指导水资源管理提供急需的信息。所使用的野外场地和由此产生的数据将用于向国家管理者、区域恢复从业者和环境专业学校的学生介绍水生生态系统研究。伯恩哈特还将利用这项研究作为平台，在北卡罗来纳州的一所理科磁石高中开设水生生态学课程，并为杜克大学的本科生提供平台。

A growing body of research demonstrates the important effect undisturbed stream ecosystems have in altering the form, timing and magnitude of watershed nitrogen (N) losses. It is less clear whether, and to what extent, this capacity is reduced during watershed degradation. Emily Bernhardt is examining whether and how critical biogeochemical functions (the removal of reactive nitrogen and community metabolism) are affected in urban streams, and whether these streams have the capacity to recover those functions through 1) longitudinal transport through unmodified landscapes (natural recovery) or 2) extensive channel reconfiguration restoration efforts (manmade solutions). Bernhardt will experimentally test whether removal rates of nitrogen are strongly carbon limited in urban streams. This is likely because the organic matter necessary to fuel microbial activity is lost in frequent stormflow events typical of urban watersheds.Ultimately this research will increase our mechanistic understanding of stream nitrogen cycling, and will provide much needed information for guiding water resources management. The field sites used and the data generated from them will be used for introducing state managers, regional restoration practitioners, and environmental professional school students to aquatic ecosystem research. Bernhardt will also use this research as a platform for classes in aquatic ecology at a NC science magnet highschool and for Duke undergraduate students.