Mechanisms of the Absence of Hypoxia in the Pearl River Estuary during Summer of 2023

Liang Chaoqi; Yang Yi; Lei Shiping; Xu Yi; Bu Dezhi; Pang Jinyan; Li Yan; Zhou Kuanbo; Guo Xianghui

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Liang Chaoqi，Yang Yi，Lei Shiping, et al. Mechanisms of the Absence of Hypoxia in the Pearl River Estuary during Summer of 2023[J]. Haiyang Xuebao，2026, 48(x)：1–14

Citation:

Liang Chaoqi，Yang Yi，Lei Shiping, et al. Mechanisms of the Absence of Hypoxia in the Pearl River Estuary during Summer of 2023[J]. Haiyang Xuebao，2026, 48(x)：1–14

Citation:

Liang Chaoqi，Yang Yi，Lei Shiping, et al. Mechanisms of the Absence of Hypoxia in the Pearl River Estuary during Summer of 2023[J]. Haiyang Xuebao，2026, 48(x)：1–14

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Mechanisms of the Absence of Hypoxia in the Pearl River Estuary during Summer of 2023

1.
State Key Laboratory of Marine Environmental Science, College of Ocean and Earth Sciences, Xiamen University, Xiamen 361102, China
2.
Fujian Provincial Key Laboratory for Coastal Ecology and Environmental Studies, Xiamen University, Xiamen 361102, China
3.
Dongshan Swire Marine Station, National Observation and Research Station for the Taiwan Strait Marine Ecosystem, Xiamen University, Zhangzhou 363499, China

Received Date: 2025-11-24
Rev Recd Date: 2026-02-13

Available Online: 2026-03-18

Abstract

Abstract

This study examines the mechanism of the unexpected absence of bottom hypoxia in the lower Pearl River Estuary during summer 2023 through integrated analysis of hydrological, biogeochemical and physical drivers. The Pear River discharge during 2023 summer was only 51% of the historical average summer average. This led to a 45% reduction in riverine nutrient fluxes and a sharp decline in marine-sourced organic carbon production. Persistent northeasterly downwelling-favorable winds during the 15 days preceding sampling weakened stratification (stratification factor of 0.074 ± 0.20 during 2023 cruise versus 0.14 ± 0.17, 0.38 ± 0.50 and 0.18 ± 0.20 during other three cruises of 2015, 2017 and 2018 when hypoxia occurred) enhanced vertical mixing and oxygen replenishment in the bottom water. The reduced river discharge also shortened the water residence time in the estuary to 1.8 days, compared to 3.1 days under average summer discharge conditions, thereby limiting the oxygen-depleting effect of organic matter degradation. The synergistic effect of these factors led to the absence of bottom-water hypoxia in the Pearl River Estuary in summer 2023. This study reveals the important regulating role of extreme hydro-meteorological conditions in the formation of estuarine hypoxia.
- Pearl River estuary,
- Pear River discharge,
- dissolved oxygen,
- hypoxia

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References(54)

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