Nutrient management offsets the effect of deoxygenation and warming on nitrous oxide emissions in a large US estuary
Weiyi Tang, Fei Da, John C. Tracey, Naomi Intrator, Moriah A. Kunes, Jenna A. Lee, Xianhui Wan, Amal Jayakumar, Marjorie A. M. Friedrichs, Bess B. Ward
Abstract
Many estuaries experience eutrophication, deoxygenation and warming, with potential impacts on greenhouse gas emissions. However, the response of N 2 O production to these changes is poorly constrained. Here we applied nitrogen isotope tracer incubations to measure N 2 O production under experimentally manipulated changes in oxygen and temperature in the Chesapeake Bay—the largest estuary in the United States. N 2 O production more than doubled from nitrification and increased exponentially from denitrification when O 2 was decreased from >20 to <5 micromolar. Raising temperature from 15° to 35°C increased N 2 O production 2- to 10-fold. Developing a biogeochemical model by incorporating these responses, N 2 O emissions from the Chesapeake Bay were estimated to decrease from 157 to 140 Mg N year −1 from 1986 to 2016 and further to 124 Mg N year −1 in 2050. Although deoxygenation and warming stimulate N 2 O production, the modeled decrease in N 2 O emissions, attributed to decreased nutrient inputs, indicates the importance of nutrient management in curbing greenhouse gas emissions, potentially mitigating climate change.