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

M. Cornejo, L. Farías
2012 Biogeosciences  
<p><strong>Abstract.</strong> Oxygen minimum zones (OMZs), such as those found in the eastern South Pacific (ESP), are the most important N<sub>2</sub>O sources in the global ocean relative to their volume. N<sub>2</sub>O production is related to low O<sub>2</sub> concentrations and high primary productivity. However, when O<sub>2</sub> is sufficiently low, canonical denitrification takes place and N<sub>2</sub>O consumption can be expected. N<sub>2</sub>O distribution in the ESP was analyzed
more » ... 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 N<sub>2</sub>O measurements. Intense N<sub>2</sub>O consumption, driving undersaturations as low as 40%, was always associated with secondary NO<sub>2</sub><sup>&amp;ndash;</sup> accumulation (SNM), a good indicator of suboxic/anoxic O<sub>2</sub> levels. First, we explore relationships between ΔN<sub>2</sub>O and O<sub>2</sub> based on existing data of denitrifying bacteria cultures and field observations. Given the uncertainties in the O<sub>2</sub> measurements, a second relationship between ΔN<sub>2</sub>O and NO<sub>2</sub><sup>&amp;ndash;</sup> (> 0.75 μM) was established for suboxic waters (O<sub>2</sub> < 8 μM). We reproduced the apparent N<sub>2</sub>O production (&amp;Delta;N<sub>2</sub>O) along the OMZ in ESP with high reliability (<i>r</i><sup>2</sup> = 0.73 <i>p</i> = 0.01). Our results will contribute to the quantification of the N<sub>2</sub>O that is recycled in O<sub>2</sub> deficient waters, and improve the prediction of N<sub>2</sub>O behavior under future scenarios of OMZ expansion and intensification.</p>
doi:10.5194/bg-9-3205-2012 fatcat:4at4fwn6ijexvcjrcmqt7ebla4