AUTHOR=Bourbonnais Annie , Frey Claudia , Sun Xin , Bristow Laura A. , Jayakumar Amal , Ostrom Nathaniel E. , Casciotti Karen L. , Ward Bess B. 

TITLE=Protocols for Assessing Transformation Rates of Nitrous Oxide in the Water Column

JOURNAL=Frontiers in Marine Science

VOLUME=8

YEAR=2021

URL=https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2021.611937

DOI=10.3389/fmars.2021.611937

ISSN=2296-7745

ABSTRACT=<p>Nitrous oxide (N<sub>2</sub>O) is a potent greenhouse gas and an ozone destroying substance. Yet, clear step-by-step protocols to measure N<sub>2</sub>O transformation rates in freshwater and marine environments are still lacking, challenging inter-comparability efforts. Here we present detailed protocols currently used by leading experts in the field to measure water-column N<sub>2</sub>O production and consumption rates in both marine and other aquatic environments. We present example <sup>15</sup>N-tracer incubation experiments in marine environments as well as templates to calculate both N<sub>2</sub>O production and consumption rates. We discuss important considerations and recommendations regarding (1) precautions to prevent oxygen (O<sub>2</sub>) contamination during low-oxygen and anoxic incubations, (2) preferred bottles and stoppers, (3) procedures for <sup>15</sup>N-tracer addition, and (4) the choice of a fixative. We finally discuss data reporting and archiving. We expect these protocols will make <sup>15</sup>N-labeled N<sub>2</sub>O transformation rate measurements more accessible to the wider community and facilitate future inter-comparison between different laboratories.</p>