Nitrogen cycling and ecological impacts mediated by water mass interactions in the Yangtze river estuary and the adjacent east China Sea: insights from nitrogen and oxygen isotopes
Ziying Zhou , Zhi Yang , Bin Wang , Haiyan Jin , Lihua Ran , Zhibing Jiang , Qianna Chen , Feng Zhou , Hao Zheng , Jianfang Chen
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引用次数: 0
Abstract
The complex hydrodynamic conditions in the Yangtze River Estuary play a pivotal role in shaping the distribution, transport, and transformation of nutrients, thereby influencing phytoplankton growth and ecosystem stability in the region. This study, based on hydrographic, biological, and chemical data collected during a mid-August 2023 cruise survey in the Yangtze River Estuary and the adjacent East China Sea, integrates nitrate nitrogen (δ15NNO3) and oxygen isotope (δ18ONO3) tracing techniques to investigate the synergistic effects of physical-biogeochemical processes during water mass convergence. The findings reveal that high concentrations of terrestrial nitrate, transported by the Changjiang Diluted Water (CDW), serve as the primary inorganic nitrogen source, driving rapid phytoplankton growth. Meanwhile, the Yellow Sea Coastal Current (YSCC) and Taiwan Warm Current (TWC) regulate nutrient transport and redistribution through mixing and convergence processes. The high phosphate input from the TWC optimizes the regional nutrient structure, alleviating phosphorus limitation caused by excessive nitrogen input from the CDW. However, the intrusion of low-oxygen YSCC waters may worsen bottom-water hypoxia. The frontal systems and water column stratification, induced by the convergence of CDW, YSCC, and TWC, control the spatial distribution of nitrogen and phosphorus nutrients, shape phytoplankton distribution patterns, and foster the formation of localized high-productivity zones. The synergistic effects of physical and biogeochemical processes, driven by water mass interactions, can significantly reduce bottom-water dissolved oxygen concentrations, thereby increasing the risk of localized hypoxia and threatening regional ecosystem stability.
期刊介绍:
Continental Shelf Research publishes articles dealing with the biological, chemical, geological and physical oceanography of the shallow marine environment, from coastal and estuarine waters out to the shelf break. The continental shelf is a critical environment within the land-ocean continuum, and many processes, functions and problems in the continental shelf are driven by terrestrial inputs transported through the rivers and estuaries to the coastal and continental shelf areas. Manuscripts that deal with these topics must make a clear link to the continental shelf. Examples of research areas include:
Physical sedimentology and geomorphology
Geochemistry of the coastal ocean (inorganic and organic)
Marine environment and anthropogenic effects
Interaction of physical dynamics with natural and manmade shoreline features
Benthic, phytoplankton and zooplankton ecology
Coastal water and sediment quality, and ecosystem health
Benthic-pelagic coupling (physical and biogeochemical)
Interactions between physical dynamics (waves, currents, mixing, etc.) and biogeochemical cycles
Estuarine, coastal and shelf sea modelling and process studies.