Responses of nutrient biogeochemistry and nitrogen cycle to seasonal upwelling in coastal waters of the eastern Hainan Island

Nan Zhou; Sumei Liu; Guodong Song; Yunyan Zhang; Lingyan Wang; Xiaoyan Ning

doi:10.1007/s13131-021-1934-8

Volume 41 Issue 6

Jun. 2022

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Nan Zhou, Sumei Liu, Guodong Song, Yunyan Zhang, Lingyan Wang, Xiaoyan Ning. Responses of nutrient biogeochemistry and nitrogen cycle to seasonal upwelling in coastal waters of the eastern Hainan Island[J]. Acta Oceanologica Sinica, 2022, 41(6): 99-113. doi: 10.1007/s13131-021-1934-8

Citation:

Nan Zhou, Sumei Liu, Guodong Song, Yunyan Zhang, Lingyan Wang, Xiaoyan Ning. Responses of nutrient biogeochemistry and nitrogen cycle to seasonal upwelling in coastal waters of the eastern Hainan Island[J]. Acta Oceanologica Sinica, 2022, 41(6): 99-113. doi: 10.1007/s13131-021-1934-8

Citation:

Nan Zhou, Sumei Liu, Guodong Song, Yunyan Zhang, Lingyan Wang, Xiaoyan Ning. Responses of nutrient biogeochemistry and nitrogen cycle to seasonal upwelling in coastal waters of the eastern Hainan Island[J]. Acta Oceanologica Sinica, 2022, 41(6): 99-113. doi: 10.1007/s13131-021-1934-8

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Responses of nutrient biogeochemistry and nitrogen cycle to seasonal upwelling in coastal waters of the eastern Hainan Island

doi: 10.1007/s13131-021-1934-8

Nan Zhou^{1, 2},
Sumei Liu^{1, 2
,
,},
Guodong Song^{1, 2},
Yunyan Zhang^{1, 2},
Lingyan Wang^{1, 2},
Xiaoyan Ning^{1, 2}

1.
Frontiers Science Center for Deep Ocean Multispheres and Earth System, and Key Laboratory of Marine Chemistry Theory and Technology of Ministry of Education, Ocean University of China, Qingdao 266100, China
2.
Laboratory for Marine Ecology and Environmental Science, Pilot National Laboratory for Marine Science and Technology (Qingdao), Qingdao 266237, China

Funds: The National Natural Science Foundation of China under contract No. 41376086; the Taishan Scholars Programme of Shandong Province; the Aoshan Talents Program supported by the Pilot National Laboratory for Marine Science and Technology (Qingdao) under contract No. 2015ASTP-OS08.

More Information

Corresponding author: E-mail: sumeiliu@ouc.edu.cn
Received Date: 2021-05-31
Accepted Date: 2021-10-11

Available Online: 2022-03-28

Publish Date: 2022-06-16

Abstract

Abstract

The coastal upwelling has profound influence on the surrounding ecosystem by supplying the nutrient-replete water to the euphotic zone. Nutrient biogeochemistry was investigated in coastal waters of the eastern Hainan Island in summer 2015 and autumn 2016. From perspectives of nutrient dynamics and physical transport, the nutrient fluxes entered the upper 50 m water depth (between the mixed layer and the euphotic zone) arisen from the upwelling were estimated to be 2.5−5.4 mmol/(m²·d), 0.15−0.28 mmol/(m²·d), and 2.2−7.2 mmol/(m²·d) for dissolved inorganic nitrogen (DIN), phosphate (DIP), and dissolved silicate (DSi), respectively, which were around 6- to 12-fold those in the background area. The upwelled nutrients supported an additional plankton growth of (14.70±8.95) mg/m² for chlorophyll a (Chl a). The distributions of nitrate δ¹⁵N and δ¹⁸O above the 300 m water depth (top of the North Pacific Intermediate Water) were different among the upwelling area, background area in summer, and the stations in autumn, and the difference of environmental and biogeochemical conditions between seasons should be the reason. The higher DIN/DIP concentration ratio, nitrate concentration anomaly, and lower nitrate isotope anomaly (Δ(15, 18)) in the upper ocean in summer than in autumn indicated the stronger nitrogen fixation and atmospheric deposition, and the following fixed nitrogen regeneration in summer. The higher values of Chl a and nitrate δ¹⁵N and δ¹⁸O within the euphotic zone in autumn than the background area in summer suggested the stronger nitrate assimilation in autumn. The differences in relatively strength of the assimilation, nitrogen fixation and atmospheric deposition, and the following remineralization and nitrification between the two seasons made the higher δ¹⁸O:δ¹⁵N and larger difference of enzymatic isotope fractionation factors ¹⁵ε and ¹⁸ε for nitrate assimilation in summer than in autumn above the North Pacific Tropical Water.
- nutrients,
- upwelling,
- nitrate δ¹⁵N and δ¹⁸O,
- nitrogen cycle,
- South China Sea

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References(84)

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