Following the N2O consumption in the oxygen minimum zone of the eastern South Pacific

Oxygen minimum zones (OMZs), such as those found in the eastern South Pacific (ESP), are the most important N2O sources in the global ocean relative to their volume. N2O production is related to low O2 concentrations and high primary productivity. However, when O2 is sufficiently low, canonical denitrification takes place and N2O consumption can be expected. N2O distribution in the ESP was analyzed over a wide latitudinal and longitudinal range (from 5◦ to 30◦ S and from 71–76◦ to ∼ 84◦ W) based on ∼ 890 N2O measurements. Intense N2O consumption, driving undersaturations as low as 40 %, was always associated with secondary NO−2 accumulation (SNM), a good indicator of suboxic/anoxic O2 levels. First, we explore relationships between 1N2O and O2 based on existing data of denitrifying bacteria cultures and field observations. Given the uncertainties in the O2 measurements, a second relationship between 1N2O and NO− 2 (> 0.75 µM) was established for suboxic waters (O2 < 8 µM). We reproduced the apparent N2O production (1N2O) along the OMZ in ESP with high reliability (r 2 = 0.73 p = 0.01). Our results will contribute to the quantification of the N2O that is recycled in O2 deficient waters, and improve the prediction of N2O behavior under future scenarios of OMZ expansion and intensification.