Investigating the physical and chemical controls on aerobic methane oxidation

This project will study the variables that control the oxidation of methane in oxygenated natural waters. Methane is an important greenhouse gas. Oceans are often viewed as having the potential to release large amounts of methane to the atmosphere with warming. However, current emissions of methane from the sea surface to the atmosphere are relatively low. Local studies have shown that aerobic oxidation of methane in these natural waters helps to remove methane prior to emission. However, estimating this removal has been challenging for two reasons. First, methane oxidation measurements from different laboratories do not always agree. Second, different national conditions change the rates of aerobic methane oxidation. This project will solve these problems. This work will help determine the global importance of this methane sink, predict how methane oxidation rates will change in the future, and establish measurement protocols for greater comparability of results. Additionally, this project will engage a cohort of undergraduate students. These students will be taught oceanographic research methods centered around this project. Also, they will be coached on how to develop their own scientific interests, hypotheses, and experimental plans. Then, these students will be given the opportunity to join the research cruise associated with this work where they will enact their own experimental plans. Past participants of this program have contributed to 5 scientific publications, and 12 students have gone on to highly competitive graduate programs. This project will be accomplished through a combination of systematic laboratory experiments and environmental measurements. Investigations on the US Great Lakes and at sea along the US Atlantic Margin will be conducted to evaluate the steady-state and non-steady-state chemical kinetics of aerobic methane oxidation. This project will test the hypothesis that water temperature and methane concentration are the dominant variables governing aerobic methane oxidation with other variables of dissolved oxygen and nutrient concentrations contributing secondary influences. At the conclusion of this work, a relatively simple model will be established combining water temperature and substrate concentration(s) to predict rates of methane oxidation. 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.