Anammox and denitrification separately dominate microbial N-loss in water saturated and unsaturated soils horizons of riparian zones

Shanyun Wang, Weidong Wang, Siyan Zhao, Xiaomin Wang, Mariet M. Hefting, Lorenz Schwark, Guibing Zhu

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

Fertilized agroecosystems may show considerable leaching of the mobile nitrogen (N) compound NO3−, which pollutes groundwater and causes eutrophication of downstream waterbodies. Riparian buffer zones, positioned between terrestrial and aquatic environments, effectively remove NO3− and serve as a hotspot for N2O emissions. However, microbial processes governing NO3− reduction in riparian zones still remain largely unclear. This study explored the underlying mechanisms of various N-loss processes in riparian soil horizons using isotopic tracing techniques, molecular assays, and high-throughput sequencing. Both anaerobic ammonium oxidation (anammox) and denitrification activity were maximized in the riparian fringe rather than in the central zones. Denitrifying anaerobic methane oxidation (damo) process was not detected. Interestingly, both contrasting microbial habitats were separated by a groundwater table, which forms an important biogeochemical interface. Denitrification dominated cumulative N-losses in the upper unsaturated soil, while anammox dominated the lower oxic saturated soil horizons. Archaeal and bacterial ammonium oxidation that couple dissimilatory nitrate reduction to ammonium (DNRA) with a high cell-specific rate promoted anammox even further in oxic subsurface horizons. High-throughput sequencing and network analysis showed that the anammox rate positively correlated with Candidatus ‘Kuenenia’ (4%), rather than with the dominant Candidatus ‘Brocadia’. The contribution to N-loss via anammox increased significantly with the water level, which was accompanied by a significant reduction of N2O emission (∼39.3 ± 10.6%) since N-loss by anammox does not cause N2O emissions. Hence, water table management in riparian ecotones can be optimized to reduce NO3− pollution by shifting from denitrification to the environmentally friendly anammox pathway to mitigate greenhouse gas emissions.
Original languageEnglish
Pages (from-to)139-150
JournalWater Research
Volume162
DOIs
Publication statusPublished - 1 Oct 2019
Externally publishedYes

Funding

This research is financially supported by the National Natural Science Foundation of China (No. 41671471 , 41322012 and 91851204 ), Strategic Priority Research Program of the Chinese Academy of Sciences ( XDB15020303 ), National Key R&D Program (2016YFA0602303), Local Innovative and Research Teams Project of Guangdong Pearl River Talents Program (2017BT01Z176), special fund from the State Key Joint Laboratory of Environment Simulation and Pollution Control (Research Center for Eco-environmental Sciences, Chinese Academy of Sciences ) ( 18Z02ESPCR ), Open Research Fund of Key Laboratory of Drinking Water Science and Technology , Chinese Academy of Sciences ( 16Z03KLDWST ) and Program of the Youth Innovation Promotion Association (CAS) .

FundersFunder number
Guangdong Pearl River Talents Program2017BT01Z176
National Key R&D Program2016YFA0602303
Open Research Fund of Key Laboratory of Drinking Water Science and Technology , Chinese Academy of Sciences
National Natural Science Foundation of China41322012, 41671471, 91851204
Chinese Academy of SciencesXDB15020303, 18Z02ESPCR, 16Z03KLDWST
State Key Joint Laboratory of Environmental Simulation and Pollution Control
Youth Innovation Promotion Association

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