Award: OCE-2022991

This project sought to better understand how the presence or absence of oxygen affects the rate at which the gas nitrous oxide (N₂O) is produced and consumed in seawater. Nitrous oxide has attracted considerable scientific attention, as the cycling of this compound affects the availability of the essential nutrient nitrogen (N) for marine food webs. Moreover, the fate of N₂O is controlled by the metabolisms of microorganisms, many of which are sensitive to changes in oxygen content that are becoming increasingly common in coastal and open ocean environments. Intellectual Merit: To explore the link between oxygen and N₂O flux, this project united scientists from over five institutions to conduct field experiments and microbiological analyses of a model low oxygen fjord off British Columbia. Fortuitiously, while conducting fieldwork in the fjord, a small pulse of oxygen-rich water mixed into the low oxygen zone, allowing a rare opportunity to describe how the microbial ecosystem responded to a real-life oxygen instrusion. Oxygen intrusion significantly stimulated N₂O production while inhibiting consumption in oxygenated waters, generating oversaturated N₂O conditions for up to a week. The intrusion event also significantly affected the microbial community, resulting in changes in which microbes were metabolically active and shifting the spatial distribution of some of the most ecologically consequential community members. These results reveal that even modest oxygen intrusions can rapidly restructure marine N₂O cycling. Broader Impacts: By quantifying exactly how and to what extent N₂O cycling shifted in a natural marine ecosystem, this project helps scientists better predict how disturbances to oxygen conditions create cascading effects on the cycling of other important chemicals. This result, as well as general content knowledge on the topic of ocean biogeochemistry, was disseminated to the community through publication in open access journals, presentations at scientific conferences, and training of undergraduate and graduate students to become the next generation of scientist educators. In addition, this project supported a teacher training workshop focused on integrating marine science topics, including those at the core of this project, into middle and high school science classrooms. This workshop was conducted each summer at the Marine Institute at Sapelo Island, Georgia, with the goal of providing teachers (10-15 each year) tangible lessons plans and lab activities in marine science. All participants in the scientific and educational components of this project thank NSF for helping better understand Earth's oceans.

Last Modified: 07/15/2026
Modified by: Frank J Stewart