Nitrous Oxide Biogeochemistry in the Northern Gulf of Mexico

Abstract

Nitrous oxide (N2O) is a potent greenhouse and ozone-depleting gas produced in the ocean and released to the atmosphere. N2O can be produced in areas of low oxygen such as hypoxic areas and oxygen minimum zones. The shelf region of the northern Gulf of Mexico (GOM) experiences seasonal coastal hypoxia, and the north central GOM has an oxygen minimum layer at about a depth of 500 m. In-situ water samples from the northern Gulf of Mexico near the Deepwater Horizon oil spill site were collected and analyzed as part of the 2019 and 2021 Schade Cruises. The sample data is used to better understand the trends in the biogeochemistry and concentration of N2O in the Gulf of Mexico and to begin the timeseries of Schade Cruise N2O data. Results showed that N2O concentrations were ~1.7x higher in 2021 while Mississippi River discharge and nutrient loadings were ~ 2x and 1.5x times lower respectively. Differences in total in-situ nutrient concentrations and dissolved oxygen between 2019 and 2021 were negligible. The results illustrate the need for more consistent data from future cruises in order to accurately determine trends in N2O biogeochemistry in the northern GOM.