INT-02 Marine Nitrogen Cycle
NosZ I and NosZ II N2O-reducing bacteria co-regulate N2O reduction in the Pearl River Estuary sediments, China
Hua Xiang* , State Key Laboratory of Tropical Oceanography (LTO), South China Sea Institute of Oceanology Institute of Environmental Research at Greater Bay Area, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University
Yiguo Hong, Institute of Environmental Research at Greater Bay Area, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University
Jiapeng Wu, Institute of Environmental Research at Greater Bay Area, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University
Zheng Hu, Institute of Environmental Research at Greater Bay Area, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University
Yaohao Hu, Institute of Environmental Research at Greater Bay Area, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University
Zhiming Qu, Institute of Environmental Research at Greater Bay Area, Key Laboratory for Water Quality and Conservation of the Pearl River Delta, Ministry of Education, Guangzhou University
Aimin Long, State Key Laboratory of Tropical Oceanography (LTO), South China Sea Institute of Oceanology

Nitrous oxide (N2O) is a strong greenhouse gas and a significant source of stratosphere ozone depletion. However, the mechanism of N2O reduction mediated by bacteria in estuaries is still unknown. In this study, we investigated in situ dissolved N2O as well as the potential of N2O reduction rates (PRR), N2O emission rates (PER), denitrification rates (PDR), and proportion of N2O reduction (PNR), and key functional genes related to N2O transformation of denitrification in surface sediments of the Pearl River Estuary (PRE). The results showed that the down estuary had lower dissolved N2O compared with the upper and middle estuary. Lower PER and higher PNR were also observed in the down estuary. Similarly, the gene abundance ratios of nosZ/nir were significantly higher in the down estuary. Furthermore, NosZ II N2O-reducing bacteria have a higher abundance than that of NosZ I N2O-reducing bacteria. Besides, the community of NosZ I and NosZ II N2O-reducing bacteria also shifted from the upper estuary to the down estuary. These results suggested that NosZ I and NosZ II N2O-reducing bacteria co-regulated N2O reduction in the PRE sediments, and we propose NosZ II N2O-reducing bacteria might play a dominant role in N2O reduction.