title: Tidal pumping facilitates dissimilatory nitrate reduction in intertidal marshes.
abstract: Intertidal marshes are alternately exposed and submerged due to periodic ebb and flood tides. The tidal cycle is important in controlling the biogeochemical processes of these ecosystems. Intertidal sediments are important hotspots of dissimilatory nitrate reduction and interacting nitrogen cycling microorganisms, but the effect of tides on dissimilatory nitrate reduction, including denitrification, anaerobic ammonium oxidation and dissimilatory nitrate reduction to ammonium, remains unexplored in these habitats. Here, we use isotope-tracing and molecular approaches simultaneously to show that both nitrate-reduction activities and associated functional bacterial abundances are enhanced at the sediment-tidal water interface and at the tide-induced groundwater fluctuating layer. This pattern suggests that tidal pumping may sustain dissimilatory nitrate reduction in intertidal zones. The tidal effect is supported further by nutrient profiles, fluctuations in nitrogen components over flood-ebb tidal cycles, and tidal simulation experiments. This study demonstrates the importance of tides in regulating the dynamics of dissimilatory nitrate-reducing pathways and thus provides new insights into the biogeochemical cycles of nitrogen and other elements in intertidal marshes.
authors.affiliation: State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China.|College of Geographical Sciences, East China Normal University, Shanghai 200241, China.
authors.forename: Yanling
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China.
authors.forename: Lijun
authors.initials: L
authors.lastname: Hou
authors.affiliation: College of Geographical Sciences, East China Normal University, Shanghai 200241, China.
authors.forename: Min
authors.initials: M
authors.lastname: Liu
authors.affiliation: The University of Texas at Austin Marine Science Institute, 750 Channel View Drive, Port Aransas, Texas 78373, USA.
authors.forename: Zhanfei
authors.initials: Z
authors.lastname: Liu
authors.affiliation: College of Geographical Sciences, East China Normal University, Shanghai 200241, China.
authors.forename: Xiaofei
authors.initials: X
authors.lastname: Li
authors.affiliation: College of Geographical Sciences, East China Normal University, Shanghai 200241, China.
authors.forename: Xianbiao
authors.initials: X
authors.lastname: Lin
authors.affiliation: State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China.|College of Geographical Sciences, East China Normal University, Shanghai 200241, China.
authors.forename: Guoyu
authors.initials: G
authors.lastname: Yin
authors.affiliation: State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Gao
authors.affiliation: State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China.
authors.forename: Chendi
authors.initials: C
authors.lastname: Yu
authors.affiliation: State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China.
authors.forename: Rong
authors.initials: R
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Estuarine and Coastal Research, East China Normal University, Shanghai 200062, China.
authors.forename: Xiaofen
authors.initials: X
authors.lastname: Jiang