Collaborative Research: Impacts of atmospheric nitrogen deposition on the biogeochemistry of oligotrophic coastal waters

大气氮的沉积提供了活性氮物种，影响了氮素有限地区的初级生产。虽然人们普遍认为，这些物种在降水中对许多沿海海洋系统的人为氮负荷有很大贡献，但其生物学影响仍然知之甚少。来自宾夕法尼亚州立大学、威廉玛丽学院和老多米尼恩大学的科学家将开展一项面向过程的现场和模拟工作，以检验以下假设：夏季风暴后，大气湿氮沉积(即降水)会刺激沿海水域的初级生产力和藻类生物量的积累，这种影响超过了美国东部沿海低营养水域中风力诱导的混合和表层清新导致的层化增加的相关生物地球化学反应。为了实现他们的目标，研究人员将在夏季几个月在特拉华湾和卡罗莱纳州沿海之间的沿海水域进行拉格朗日实地实验，以确定表层生物地球化学和生物学对降水事件的响应，并将使用雷达和卫星数据进行识别和拦截。关于建模工作，一维上层海洋混合模型和一维生物地球化学上层海洋将通过同化使用伴随方法作为研究一部分获得的现场数据来校准。这一假设将通过对校准后的模型进行敏感性研究，结合现场数据和孵化实验的结果进行验证。最后，为了为野外测量和相关的一维模拟提供区域和历史背景，将进行区域大气-海洋生物地球化学联合模拟。研究结果将纳入海洋政策和海洋生物地球化学研究生课程的课堂讲课。作为该项目的一部分，宾夕法尼亚州立大学的一名研究生、威廉与玛丽学院的一名研究生以及老道明大学的一名毕业生和一名本科生将得到支持和培训。

Deposition of atmospheric nitrogen provides reactive nitrogen species that influence primary production in nitrogen-limited regions. Although it is generally assumed that these species in precipitation contributes substantially to anthropogenic nitrogen loadings in many coastal marine systems, its biological impact remains poorly understood. Scientists from Pennsylvania State University, William & Mary College, and Old Dominion University will carry out a process-oriented field and modeling effort to test the hypothesis that deposits of wet atmospheric nitrogen (i.e., precipitation) stimulate primary productivity and accumulation of algal biomass in coastal waters following summer storms and this effect exceeds the associated biogeochemical responses to wind-induced mixing and increased stratification caused by surface freshening in oligotrophic coastal waters of the eastern United States. To attain their goal, the researchers would perform a Lagrangian field experiment during the summer months in coastal waters located between Delaware Bay and the coastal Carolinas to determine the response of surface-layer biogeochemistry and biology to precipitation events, which will be identified and intercepted using radar and satellite data. As regards the modeling effort, a 1-D upper ocean mixing model and a 1-D biogeochemical upper-ocean will be calibrated by assimilating the field data obtained a part of the study using the adjoint method. The hypothesis will be tested using sensitivity studies with the calibrated model combined with in-situ data and results from the incubation experiments. Lastly, to provide regional and historical context for the field measurements and the associated 1-D modeling, linked regional atmospheric-oceanic biogeochemical modeling will be conducted.Broader Impacts. Results from the study would be incorporated into class lectures for graduate courses on marine policy and marine biogeochemistry. One graduate student from Pennsylvania State University, one graduate student from the College of William and Mary, and one graduate and one undergraduate student from Old Dominion University would be supported and trained as part of this project.