Collaborative Research: Photodegradation of Dissolved Organic Matter and its Contribution to Surface Water CO2 fluxes and the Carbon Cycle in a River Dominated Ocean Margin

海洋边缘是陆-海-气界面上的高度动态系统，在这些储存库的全球碳通量中发挥着不成比例的巨大作用。河流占主导地位的边缘接收大量的陆源溶解有机物（DOM）和它的发色组分（CDOM），是高度光反应性，似乎在很大程度上被分解为CO2在边缘表面沃茨。尽管公认的重要性，光化学过程中的河流占主导地位的边缘，地表水CO2通量的光化学的整体意义仍然不确定。在这个项目中，南卡罗来纳州哥伦比亚大学和格鲁吉亚大学的研究人员将开发区域尺度的光化学和耦合光化学-微生物碳（包括CO2和CO）通量和去除的陆源DOM和CDOM的北方墨西哥湾边缘的表面沃茨的估计。这个海洋边缘收到的主要贡献陆源DOM（3 Tg C年-1）和CDOM从密西西比河系统。具体目标包括确定表观量子产率（AQY）的光生CO2和CO，DOC的光化学去除，以及耦合的光化学-微生物去除DOC。实验确定的AQY将与实地测量，卫星图像和建模相结合，以提供在研究区域的光化学介导的碳通量的时间整合，区域尺度的评估。该项目将包括改进遥感算法和开发海洋边缘碳循环的区域规模模型。一旦开发出来，这种方法可以用来提供类似的评估在其他河流为主的海洋边缘。在海上，该项目将利用一艘机会船，并与目前资助的一项调查墨西哥湾北方边缘总二氧化碳通量和生物过程的研究相结合。这种项目的协调将提供一个前所未有的机会，了解基本的物理，生物和光化学过程控制大气-海洋CO2通量的主要河流占主导地位的边缘。更广泛的影响：测量海洋边缘的碳通量（特别是CO2和CO），并确定驱动这些通量的基本因素，已被北美碳计划和海洋碳和气候变化计划确定为非常重要的。该项目将对北美大陆主要河流之一的边缘地区地表沃茨的光化学和光化学-微生物耦合碳通量进行区域估计。该项目将为每个机构的一名研究生提供培训、经验和支助。 两位主要研究者都教授涵盖碳循环各个方面的本科生和研究生课程，从该项目收集的数据将用作这些课程的具体示例。这种将积极的研究项目的信息纳入课堂的方法已被证明是非常有效的提高学生对科学的兴趣，并鼓励本科生参与研究。

Ocean margins are highly dynamic systems at the land-sea-air interfaces, and they play a disproportionately large role in global carbon fluxes among these reservoirs. River dominated margins receive large quantities of terrigenous dissolved organic matter (DOM) and its chromophoric component (CDOM) that is highly photoreactive and appears to be largely remineralized to CO2 in margin surface waters. Despite the recognized importance of photochemical processes in river dominated margins, the overall significance of photochemistry in surface water CO2 fluxes remains uncertain. In this project, researchers at the University of South Carolina at Columbia and the University of Georgia will develop regional-scale estimates of photochemical and coupled photochemical-microbial carbon (including CO2 and CO) fluxes and removal of terrigenous DOM and CDOM in surface waters of the northern Gulf of Mexico margin. This ocean margin receives major contributions of terrigenous DOM (3 Tg C yr-1) and CDOM from the Mississippi River system. Specific objectives include determination of apparent quantum yields (AQY) for the photoproduction of CO2 and CO, the photochemical removal of DOC, and the coupled photochemical-microbial removal of DOC. Experimentally determined AQYs will be used in combination with field measurements, satellite imagery, and modeling to provide temporally-integrated, regional-scale assessments of photochemically-mediated carbon fluxes in the study region. The project will include improvement of remote-sensing algorithms and the development of regional-scale models for ocean margin carbon cycling. Once developed, this approach can be utilized to provide similar assessments in other river dominated ocean margins. At sea, the project will utilize a ship of opportunity and integrate with a currently funded study investigating total CO2-fluxes and biological processes in the northern Gulf of Mexico margin. This coordination of projects will provide an unprecedented opportunity for understanding the fundamental physical, biological, and photochemical processes controlling air-sea CO2 fluxes in a major river dominated margin. Broader Impacts: Measuring carbon fluxes (specifically CO2 and CO) in ocean margins and identifying the fundamental factors driving these fluxes have been identified as of great importance by the North American Carbon Program and Ocean Carbon and Climate Change programs. This project will provide regional estimates of photochemical and coupled photochemical-microbial carbon fluxes in surface waters of one of the major river dominated margins of the North American continent. This project will provide training, experience and support for a graduate student at each institution. Both principal investigators teach undergraduate and graduate classes that cover various aspects of the carbon cycle, and data collected from this project will be used as specific examples in these classes. This approach of incorporating information from active research programs into the classroom has proven to be very effective for increasing student interest in science and has encouraged undergraduate participation in research.