Collaborative Research: Rivers and the Carbon Cycle: A Mechanistic Basis for Dissolved Organic Carbon Removal

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Streams and rivers are important for the removal of organic matter transported from land as water moves across landscapes. Many questions remain about how organic matter is removed from freshwaters. A key challenge is that not all organic matter is the same. Organic matter dissolved in freshwaters is made up of many different compounds. These compounds range in age, source, and chemical composition, all of which can influence how fast they are processed. To overcome this challenge, researchers will collect real-time sensor data and design field-scale experiments to measure how fast organic matter is removed by streams. The project aims to test hypotheses about what processes control the removal of different types of organic matter from streams and rivers. This is important because organic matter provides energy that supports food webs, and can pollute downstream ecosystems. Organic matter processing can also determine rates of greenhouse emissions from streams and rivers to the atmosphere. This research will also provide valuable opportunities for high school teachers to engage in investigations that will enhance their ability to meet Next-Generation Science standards.What processes drive organic carbon removal in streams, and how does organic carbon removal regulate the degree to which running waters are biological reactors versus exporters of organic carbon? These are key unresolved questions in carbon cycle research. This project will develop a proof-of-concept approach to test the hypothesis that non-additive effects of mixed organic matter sources (i.e. priming) control organic carbon removal in streams. Data products will include estimates of organic carbon turnover distance derived from ecosystem metabolism and stream chemistry, as well as empirical measures of organic carbon removal from ecosystem-level experiments that use single-source and mixed organic carbon additions. Project data and computer source codes will be shared openly via HydroShare and GitHub, respectively. The research will be conducted at Flathead Lake Biological Station and the researchers will partner with the Station?s recently funded SensorSpace, a community facility for construction and testing of novel environmental sensors, as well as a test bed for integrating sensor-based data into Next-Generation Science curricula.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.