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Radium-traced nutrient outwelling from the Subei Shoal to the Yellow Sea: Fluxes and environmental implication

Abstract

The Subei Shoal is the largest sandy ridge in the southern Yellow Sea and is important source for nutrient loading to the sea. Here, the nutrient fluxes in the Subei Shoal associated with eddy diffusion and submarine groundwater discharge (SGD) were assessed to understand their impacts on the nutrient budget in the Yellow Sea. Based on the analysis of 223Ra and 224Ra in the field observation, the offshore eddy diffusivity mixing coefficient and SGD were estimated to be 2.3×108 cm2/s and 2.6×109 m3/d (16 cm/d), respectively, in the Subei Shoal. Combined the significant offshore decreasing gradients of nutrient in seawater of the Subei Shoal, the spatially integrated nutrient outwelling fluxes to the Yellow Sea were 262–1 465 µmol/(m2·d) for DIN, 5.2–21 µmol/(m2·d) for DIP and 711–913 µmol/(m2·d) for DSi. Compared to the riverine input, atmospheric deposition and mariculture, nutrient outwelling from the Subei Shoal might play an important role in nutrient budget of the Yellow Sea. These nutrient fluxes could provide 4.1%–23% N and 1.3%–5.3% P requirements for the primary productivity, and the deviated DIN/DIP ratios have the potential to affect the growth of phytoplankton in the marine ecosystem of the Yellow Sea.

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Acknowledgements

We thank Captain Lin Wei and the crew on R/V SURUYUYUN-288 for their assistance in the sample collection. We thank Wanli Xing and Qian Ma from SKLEC/ECNU for their help in field observations.

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Correspondence to Jinzhou Du.

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Foundation item: The National Science and Technology Major Project of the Ministry of Science and Technology of China under contract No. 2016YFC1402106; the National Natural Science Foundation of China under contract Nos 41376089, 41576083, 41976040, 41876127 and 42030402; the China Postdoctoral Science Foundation under contract No. 2020M671048.

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Liu, J., Liu, D. & Du, J. Radium-traced nutrient outwelling from the Subei Shoal to the Yellow Sea: Fluxes and environmental implication. Acta Oceanol. Sin. 41, 12–21 (2022). https://doi.org/10.1007/s13131-021-1930-z

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  • DOI: https://doi.org/10.1007/s13131-021-1930-z

Key words

  • nutrient outwelling
  • eddy diffusion
  • submarine groundwater discharge
  • radium isotopes
  • Subei Shoal
  • Yellow Sea