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

Abstract. Nitrous oxide (N2O) is an important ozone-depleting greenhouse gas produced and consumed by microbially mediated nitrification denitrification pathways. Estuaries are intensive N2O emission regions in marine ecosystems. However, the potential contributions of nitrifiers denitrifiers to sources sinks China's estuarine coastal areas poorly understood. The abundance transcription six key microbial functional genes involved denitrification, as well clade II-type nosZ gene-bearing community composition reducers, were investigated four estuaries spanning Chinese coastline. results showed that ammonia-oxidizing archaeal amoA transcripts more dominant northern Bohai Sea (BS) Yangtze River estuaries, which had low nitrogen concentrations, while denitrifier nirS southern Jiulong (JRE) Pearl high levels terrestrial input. Notably, II gene was abundant than I-type throughout except for JRE a few sites BS, opposite transcript distribution pattern observed these two estuaries. distributions significantly constrained oxygen concentrations salinity, temperature, pH. along coastline level diversity distinctly different from soil oxygen-minimum-zone waters. By comparing patterns across with concentration flux, we found may principally control emissions pattern.