2026-02-04 中国科学院（CAS）
Schematic diagram of nitrogen cycling in intertidal groundwater. (Image by Prof. XIAO Kai’s team)
＜関連情報＞
- https://english.cas.cn/newsroom/research_news/earth/202602/t20260204_1149785.shtml
- https://www.sciencedirect.com/science/article/abs/pii/S0022169426000776
堆積物の垂直成層は、潮間帯に沿った溶存栄養素の動態と界面フラックスを制御する Vertical sediment stratification regulates dissolved nutrient dynamics and interface fluxes along the intertidal zone
Zhenyang Li, Yueqi Wang, Yashu Qi, Kai Xiao, Guangxuan Han, Hailong Li, Liang Liu, Dejuan Jiang, Xiaoying Zhang, Chunmiao Zheng
Journal of Hydrology Available online: 19 January 2026
DOI:https://doi.org/10.1016/j.jhydrol.2026.134980
Highlights
- Fine-over-coarse stratigraphy shaped distinct nutrient and carbon distributions.
- Carbon-to-nitrogen stoichiometry governed intertidal groundwater nitrogen cycling.
- Fine-grained layer enhanced NH4+ export and elevated DIN/DIP and DIN/DSi ratios.
Abstract
Sediment stratification is a ubiquitous feature in intertidal aquifers, yet its precise role in regulating dissolved nutrient dynamics remains poorly understood. This study examined two typical kinds of intertidal transects including the sandy beach and mudflat, each exhibiting distinct sediment stratification. We analyzed the multi-depth distribution patterns of dissolved nutrients (nitrogen, phosphorus, and silicon) and carbon in intertidal groundwater. We also identified the key drivers using stable isotope tracers (δ15N-NO3− and δ18O-NO3−) and multivariate statistics, and quantified the interface fluxes to the coastal ocean. The findings indicated that the distribution patterns of nutrients and carbon between fine- and coarse-grained sediments in both transects were synthetically influenced by hydrological dynamics and biogeochemical reactions. In the sandy beach, groundwater composition transitioned from being NO3−-dominated in the deep coarse-grained sediments, where attenuation occurred via denitrification, to NH4+-dominated in the surface fine-grained sediments due to organic matter mineralization. In the mudflat, organic-rich sediments and low water exchange rates favored NH4+ dominance, with fine-grained sediments accumulating high concentrations of NH4+, PO43−, and DSi in groundwater. Moreover, the sandy beach served as hotspots for groundwater discharge, delivering nutrient and dissolved carbon fluxes up to two orders of magnitude higher than the mudflat. The presence of a surface fine-grained sediments enhanced the export of groundwater-derived NH4+ and DIC, potentially exacerbating coastal eutrophication and acidification. These findings demonstrate that sediment stratification fundamentally alters the composition and flux magnitude of nutrients and carbon discharged into coastal waters, thereby influencing coastal solute budgets.
