This $1,038,171 project grant from the National Science Foundation's Geosciences program (CFDA 47.050) supports research into methane efflux from river-influenced coastal marine sediments in the Gulf of Mexico. The Louisiana Universities Marine Consortium will measure methane fluxes from coastal sediments into Gulf waters using an in situ lander to collect benthic flux measurements of oxygen and methane. Sediment microprofiles of oxygen and sulfide will also be analyzed. Naturally occurring radioisotopes will be used to determine sedimentation and mixing rates, while radiotracers and geochemical analysis will measure sulfate reduction and methane oxidation rates. During two cruises, fluxes will be measured at five sites to refine understanding of interactions between rivers, sediments, and methane releases. The awardee will also support the development of an early career investigator and provide research training for students. Broader impacts include education and outreach efforts to communicate findings to scientists, students, policymakers, and the public.