Hydrodynamics and Biogeochemistry of East China Sea Systems

The East China Sea is characterised by a complex interplay of freshwater discharge, shelf currents and open‐ocean intrusions that drive both physical and chemical variability. Seasonally varying outflow from the Changjiang River forms a buoyant plume that interacts with tidal and wind‐driven currents to generate fronts, eddies and internal waves. To the south and east, the Kuroshio Current intrudes onto the shelf, supplying high‐salinity water and oceanic nutrients that modulate stratification and mixing. These hydrodynamic processes control vertical and horizontal nutrient fluxes, setting the stage for primary production and microbial community assembly.

On the biogeochemical side, inorganic nutrients delivered by rivers and upwelled from oceanic sources fuel phytoplankton growth and organic matter production. Dissolved organic nutrients, notably conservative fractions of nitrogen and phosphorus, can be transported hundreds of kilometres from their source, altering nutrient stoichiometry in surface waters. The balance between nutrient supply, light availability and mixing depth regulates bloom dynamics, carbon export and oxygen budgets across the shelf.

Understanding the coupled hydrodynamic–biogeochemical system of the East China Sea is essential for predicting fisheries yield, harmful algal blooms and the region’s role in the global carbon cycle. Recent advances in high‐resolution modelling, autonomous sampling and molecular techniques are shedding new light on seasonal transitions, cross‐shelf exchanges and the long-range transport of both inorganic and organic nutrients.

Research from Nature Portfolio

Seminal work has demonstrated that dissolved organic nutrients from the Changjiang River behave as conservative tracers over distances exceeding 800 km in summer surface waters. While dissolved inorganic nitrogen is rapidly depleted within the nearshore zone, dissolved organic nitrogen and phosphorus persist far offshore, implying a critical role in sustaining microbial and phytoplankton communities well beyond the river mouth. This finding challenges previous assumptions about nutrient removal and highlights the importance of organic forms in driving shelf biogeochemistry and carbon cycling.

Hydrodynamics and Biogeochemistry of East China Sea Systems publication trend

The graph below shows the total number of articles in hydrodynamics and biogeochemistry of east china sea systems across all publications each year (not limited to Nature Index journals).

Technical terms

Hydrodynamics: The study of fluid motion, encompassing currents, tides, mixing and wave processes that transport water masses and tracers in the marine environment.

Biogeochemistry: The examination of chemical cycles (e.g., carbon, nitrogen, phosphorus) and their interactions with biological and physical processes in natural waters.

Changjiang River plume: A buoyant, freshwater‐dominated flow that extends from the river mouth into the shelf, forming fronts, eddies and mixing zones critical for nutrient distribution.

Stratification: A vertically layered structure in the water column arising from density differences, usually driven by temperature or salinity gradients, which influences mixing depth and light penetration.

Nutrient flux: The rate at which chemical nutrients cross a defined boundary (e.g., river mouth or shelf break), often expressed in moles per unit time.

Conservative behaviour: A characteristic of tracers whose concentration changes only by physical mixing and dilution, with negligible sources or sinks through biological uptake or chemical transformation.

References

1. Microbial community diversity from nearshore to offshore in the East China Sea. Frontiers in Microbiology (2024).
2. The Relationship between Chlorophyll Concentration and ENSO Events and Possible Mechanisms off the Changjiang River Estuary. Remote Sensing (2023).
3. Advances on Coastal and Estuarine Circulations Around the Changjiang Estuary in the Recent Decades (2000–2020). Frontiers in Marine Science (2021).
4. Significant and conservative long-range transport of dissolved organic nutrients in the Changjiang diluted water. Scientific Reports (2018).