Nitrous oxide production by salt marsh sediment fungi: its significance and mechanisms

Nitrous oxide is a potent greenhouse gas and ozone-depleting substance released from natural and agricultural environments. Coastal wetlands are one of the largest natural sources of nitrous oxide to the atmosphere, with most of the gas flux attributed to microbial processes in the sediment. In soil environments, fungi are significant contributors to nitrous oxide production, but in coastal wetlands the role of fungi is largely unknown. This project examines the role of understudied fungi in nitrous oxide production in salt marshes under varying environmental conditions in isolated fungal cultures and field-collected salt marsh sediments. Research findings are expected to improve future climate predictions and guide the restoration and management of salt marsh habitats to reduce nitrous oxide production. In addition to research training graduate and undergraduate students, this project will enhance scientific and conservation training to local high school students from diverse backgrounds through a partnership with a local zoo. This project aims to estimate the overall contribution of fungi to nitrous oxide release from salt marsh sediments and determine the metabolic basis for fungal nitrous oxide production under different oxidation-reduction and nutrient conditions. The researchers will cultivate fungi isolated from marsh sediments and use transcriptional profiling to reveal key genes that control nitrous oxide production. They hypothesize that salt marsh fungi produce nitrous oxide primarily by the anaerobic respiration of nitrate or nitrite. The project will constrain the contribution of fungi to nitrous oxide production with novel 15N-tracer incubations and inhibition of either the prokaryotic (i.e., bacteria) or the eukaryotic (i.e., fungi) components of the microbial community. This project will improve understanding of how microbial fungi survive the absence of oxygen and drastic daily changes in oxidation-reduction conditions. This project is jointly funded by Ecosystem Science and the Established Program to Stimulate Competitive Research (EPSCoR). 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.