Gross nitrogen transformations in intertidal sediments of the Yangtze Estuary: Distribution patterns and environmental controls

作者：Chen, Shuntao; Gao, Dengzhou; Zhang, Jinbo; Zheng, Yanling; Li, Xiaofei; Dong, Hongpo; Yin, Guoyu; Han, Ping; Liang, Xia; Liu, Min; Mueller, Christoph; Hou, Lijun^*

来源：Geoderma, 2023, 429: 116233.

DOI：10.1016/j.geoderma.2022.116233

• Gross N transformation rates
• 15N-tracing study
• Numerical model optimization
• Intertidal sediment
• Yangtze Estuary

Nitrogen (N) transformations in estuarine and coastal ecosystems play a crucial role in the global biogeochemical cycles. However, simultaneous estimation of gross N transformations and the underlying drivers across estuarine and intertidal wetlands remain poorly understood. Here, the spatial changes in gross N transformation rates and related functional gene abundances were explored in varying habitats of the intertidal zone in the Yangtze Es-tuary via an optimized 15N tracing model and quantitative PCR. The results indicate that the gross N trans-formation rates changed remarkably in estuarine and intertidal wetlands, with comparatively higher gross N transformation rates at the upper freshwater and low-salinity sites relative to high-salinity sites. Meanwhile, the functional gene abundances (amoB, UreC, hzo, nirS and nrfA) exhibited a similar spatial distribution pattern to corresponding N transformation processes. Sedimentary total organic carbon (TOC), nitrite (NO2-), ferrous iron (Fe(II)), and microbial functional gene abundances jointly mediated the gross N transformations. This study carried out the first simultaneous estimation of the gross N transformation pattern and driving factors in estu-arine and intertidal ecosystems based on the optimized 15N tracing model, providing a better understanding of internal mechanisms on the N cycling and strategy for estuarine and coastal N management.

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