The influence of climate on in‐stream removal of nitrogen

Nitrogen (N) removal via benthic denitrification in large river systems can be a significant sink of terrestrial N and a source of nitrous oxide (N 2 O) to the atmosphere. Recent studies have demonstrated the fraction of in‐stream N removed from a river reach is related to the water residence time. We used the HYDRA aquatic transport model to examine the sensitivity of in‐stream N removal and the associated N 2 O emissions in the Mississippi River system to the interannual variability in climate. The results suggested an almost two‐fold range in the percent of N removed in the Mississippi River system and a three‐fold range in the associated N 2 O emissions, with the lowest percent removed (10–33%) and the highest N 2 O emissions (15.5–26.0 10 6 kg N) occurring in the wettest years. The results demonstrate the importance of considering climate variability and change in the management of nutrient export by large rivers.