COLLABORATIVE PROPOSAL: HOW IMPORTANT IS "OLD" CARBON IN LAKE SUPERIOR? A RADIOCARBON INVESTIGATION

存在于水生生态系统中的有机碳有可能被沉积的有机物隔离，或者通过微生物呼吸循环并贡献到大气中。最终，有机物的命运取决于它的来源，以及它在水柱中暴露的物理运输机制和生物地球化学转化。由于这些过程在水生系统（如海洋）内变化很大，因此很难评估有机碳的生物地球化学重要性；然而，这是一个至关重要的问题，其结果可以用来解决全球生物地球化学碳循环的关键问题，并确定大多数水生环境的净异养。明尼苏达大学德卢斯分校和弗吉尼亚联邦大学的科学家将通过研究苏必利尔湖的有机碳动态来解决这个问题，因为它的生物地球化学与世界海洋相似。研究人员计划将苏必利尔湖作为天然实验室，开展颗粒有机碳（POC）、溶解有机碳（DOC）、溶解无机碳（DIC）和细菌呼吸CO2的放射性碳测量，并获得分层和非分层时期DOC和POC的化学组成。研究结果将用于确定湖泊中碳的来源，并确定POC、DOC、DIC和细菌呼吸CO2之间的碳转化。教育影响包括为K-12观众举办研讨会和演讲，以及为研究生和本科生提供水资源科学和生物化学课程的研究和培训机会。

Organic carbon present in aquatic ecosystems has the potential to either be sequestered by sedimentary organic matter or recycled and contributed to the atmosphere through microbial respiration. Ultimately, the fate of organic matter is dependant upon its source, as well as the physical transport mechanisms and biogeochemical transformations it is exposed to in the water column. Because these processes vary significantly within aquatic systems, such as the ocean, it is difficult to assess the biogeochemical importance of organic carbon; however, it is a problem of critical importance whose results could be utilized to resolve key issues in global biogeochemical carbon cycles and to determine the net heterotrophy of most aquatic environments. Scientists from the University of Minnesota-Duluth and Virginia Commonwealth University would address this problem by studying organic carbon dynamics in Lake Superior because its biogeochemistry is similar to that of the world ocean. Using Lake Superior as a natural laboratory, the researchers plan to carry out radiocarbon measurements of particulate organic carbon (POC), dissolved organic carbon (DOC), dissolved inorganic carbon (DIC), and bacterially-respired CO2, as well as obtain the chemical composition of DOC and POC during stratified and non-stratified periods. Results would be used to identify the sources of carbon in the lake and determined transformations of carbon between POC, DOC, DIC, and bacterially-respired CO2. Educational impacts include workshops and presentation for K-12 audiences as well as research and training opportunities for graduate and undergraduate students in Water Resources Science and Biochemistry classes.