Hypoxia and upwelling co-occurred in the summer, and the well-mixed water often reaches the subsurface in the East China Sea (ECS), especially off the Changjiang River estuary. The impact of upwelling on the hypoxia and, therefore, on the ECS ecosystem is not well evaluated. This study demonstrates several positive and negative effects of upwelling on hypoxia and its impact on the ecosystem. This dataset contains data collected from four cruises in the summer of 2003 (June 18–26 and August 13–23) and 2014 (July 16–29 and August 20–31) on the R/V Ocean Researcher I and V in the East China Sea described in the paper: “Chung-Chi Chen, Dong S. Ko, Gwo-Ching Gong, Chun-Chi Lien, Wen-Chen Chou, Hung-Jen Lee, Fuh-Kwo Shiah, Yu-Sin Wita Huang (2022). Reoxygenation of the hypoxia in the East China Sea: A ventilation opening for marine life. Frontiers in Marine Science “. The presented variables include: temperature, salinity, dissolved oxygen, dissolved inorganic nutrients (nitrate and phosphate), and Chl a in this study.

Main results of this study included nine figures and two tables as described in the paper, and please refer it for further details.

The designed sampling stations were located throughout the East China Sea, but the sampling stations in different sampling periods varied. Conductivity, temperature, and depth (CTD) were recorded throughout the water column with a CTD instrument (SBE9/11 Plus; Sea-Bird Electronic Inc., Bellevue, WA, USA). The water samples were collected in Teflon-coated Go-Flo bottles (20 L; General Oceanics Inc., Miami, GL, USA) mounted on a Rosette assembly (Model 1015; General Oceanics Inc.). At each station, 5–10 samples were taken at depths of 2–50 m, depending on the water depth. Subsamples were taken for immediate analyses (DO, dissolved inorganic nutrients, and Chl a). The analyzed methods for each variable can be found from the paper. The data has been processed by a linear regression analysis using “SigmaStat” to produce a ms accepted for publication in Frontiers in Marine Science.

The “Readme_Reoxygenation” file contains an explanation of each of the variables in the dataset, its measurement units. Information on how the measurements were done or data were retrieve can be found in the associated manuscript referenced above.