Preprints
https://doi.org/10.5194/bg-2022-43
https://doi.org/10.5194/bg-2022-43
 
13 Apr 2022
13 Apr 2022
Status: this preprint is currently under review for the journal BG.

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

Xiaofeng Dai1, Mingming Chen1, Xianhui Wan2, Ehui Tan3, Jialing Zeng1, Nengwang Chen1,4, Shuh-Ji Kao1,3, and Yao Zhang1 Xiaofeng Dai et al.
  • 1State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361005, China
  • 2Department of Geosciences, Princeton University, NJ 08540, USA
  • 3State Key Laboratory of Marine Resource Utilization in South China Sea, Hainan University, Haikou, Hainan, China
  • 4Fujian Provincial Key Laboratory for Coastal Ecology and Environmental Studies, College of the Environment and Ecology, Xiamen University, Xiamen 361005, China

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

Xiaofeng Dai et al.

Status: open (until 16 Jun 2022)

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  • RC1: 'Comment on bg-2022-43', Anonymous Referee #1, 12 May 2022 reply

Xiaofeng Dai et al.

Xiaofeng Dai et al.

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Short summary
This study revealed the distinct distribution patterns of six key microbial functional genes and transcripts related to N2O production and consumption pathways, the diversity and community structure of the clade II-type nosZ gene, and the environmental factors influencing the distribution, the transcription, and the diversity and community structure in China’s estuaries. N2O produced by denitrification may be more important in determining the N2O emissions patterns across the estuaries.
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