Nitrogen and oxygen availabilities control water column nitrous oxide production during seasonal anoxia in the Chesapeake Bay

Abstract

Abstract. Nitrous oxide (N2O) is a greenhouse gas and an ozone depletion agent. Estuaries that are subject to seasonal anoxia are generally regarded as N2O sources. However, insufficient understanding of the environmental controls on N2O production results in large uncertainty about the estuarine contribution to the global N2O budget. Incubation experiments with nitrogen stable isotope tracer were used to investigate the geochemical factors controlling N2O production from denitrification in the Chesapeake Bay, the largest estuary in North America. The highest potential rates of water column N2O production via denitrification (7.5±1.2 nmol-N L−1 h−1) were detected during summer anoxia, during which oxidized nitrogen species (nitrate and nitrite) were absent from the water column. At the top of the anoxic layer, N2O production from denitrification was stimulated by addition of nitrate and nitrite. The relative contribution of nitrate and nitrite to N2O production was positively correlated with the ratio of nitrate to nitrite concentrations. Increased oxygen availability, up to 7 µmol L−1 oxygen, inhibited both N2O production and the reduction of nitrate to nitrite. In spring, high oxygen and low abundance of denitrifying microbes resulted in undetectable N2O production from denitrification. Thus, decreasing the nitrogen input into the Chesapeake Bay has two potential impacts on the N2O production: a lower availability of nitrogen substrates may mitigate short-term N2O emissions during summer anoxia; and, in the long-run (timescale of years), eutrophication will be alleviated and subsequent reoxygenation of the bay will further inhibit N2O production.

Potential contributions of nitrifiers and denitrifiers to nitrous oxide sources and sinks in China's estuarine and coastal areas

“…For example, nitrification was credited as the dominant N 2 O production pathway in the Scheldt Estuary as well as in some other European estuaries (Barnes and Upstill-Goddard, 2011;Brase et al, 2017;De Wilde and De Bie, 2000;Li et al, 2015), while an inverse correlation between N 2 O concentrations and oxygen indicates that denitrifiers might be the dominant N 2 O contributor in the Potomac River estuary (McElroy et al, 1978). In addition, the incubation experiments with nitrogen-stable isotope tracers reveal active N 2 O production by denitrification in the Chesapeake Bay (Ji et al, 2018b). Another research project in the Chesapeake Bay reveals that physical processes such as wind events and vertical mixing affect the net balance between N 2 O production and consumption, resulting in a variable source and sink for N 2 O (Laperriere et al, 2019).…”

“…Nitrous oxide (N 2 O) is a kind of ozone-depleting substance and an important, long-lived greenhouse gas with a global warming potential 298 times that of carbon dioxide (CO 2 ) (Solomon et al, 2007;Ravishankara et al, 2009;Rowley et al, 2013). Prokaryotic microorganisms play an important role in N 2 O production and consumption through the nitrification and denitrification pathways (Babbin et al, 2015;Domeignoz-Horta et al, 2015;Ji et al, 2018b;Meinhardt et al, 2018;Santoro et al, 2011;Silvennoinen et al, 2008). N 2 O is produced as a byproduct in the first step (NH + 4 →NO − 2 ) of nitrification, which is catalyzed by ammonia monooxygenase in ammonia-oxidizing archaea (AOA) and ammonia-oxidizing bacteria (AOB) (Codispoti and Christensen, 1985).…”

The potential of ryegrass as cover crop to reduce soil N2O emissions and increase the population size of denitrifying bacteria

“…. The relationships between soil NO 3 − and N 2 O emissions indicate that, under these conditions, soil NO 3 − is the predominant factor controlling soil N 2 O emissions (Dong et al, 2018;Ji et al, 2018;Zhou, Zhu, Wang, & Wang, 2017). At 60% WFPS, both nitrification and denitrification are expected to be important contributors to soil N 2 O emissions, as this moisture level is seen as the threshold between aerobic and anaerobic conditions (Köbke et al, 2018;Menéndez, Barrena, Setien, González-Murua, & Estavillo, 2012;Volpi, Laville, Bonari, o di Nasso, & Bosco, 2017).…”

The influence of mesoscale climate drivers on hypoxia in a fjord-like deep coastal inlet and its potential implications regarding climate change and greenhouse gas production: examining a decade of water quality data

“…Depending on the amount of available DO, the eventual end product of ammonia oxidation (first step of nitrification) may differ (Arrigo 2005;Codispoti et al 2005;Lam et al 2011). At suboxic concentrations, ammonia oxidation begins to favour the production of N2O (a potent greenhouse gas; GHG) over NO2 - (Goreau et al 1980;Ji et al 2018;Frey et al 2020;). Da Silva et al (2021) observed significant differences in the microbial communities present in the Harbour's basin waters, with communities comprising a more significant proportion of GHG producers than in the surface waters.…”