Nitrous Oxide on the Texas-Louisiana Continental Shelf: No Laughing Matter
Samples were collected at various locations and depths in the northern Gulf of Mexico during June 2018 and July 2019 and analyzed using gas chromatography with electron capture detection. In 2018, 10 stations were sampled between June 22 and June 24, one of which was hypoxic. Surface N2O concentrations ranged from 5 to 7 nM, and water column concentrations ranged from 5 to 9 nM. There was no significant difference in N2O concentrations between the hypoxic station and the non-hypoxic stations. In 2019, 14 stations were sampled between July 4 and July 6, four of which were hypoxic. Surface N2O concentrations ranged from 2 to 7 nM, and water column concentrations ranged from 0.4 and 7 nM. For two hypoxic stations, very low and decreasing concentrations of N2O (0.4 - 1 nM) corresponded with increasing NO2- and NO3- concentrations in the presence of low oxygen. Generally, N2O concentrations are lower and more variable in 2019 despite increased observed hypoxia.