Low dissolved oxygen in the Pearl River estuary in summer: Long-term spatio-temporal patterns, trends, and regulating factors

Several large semi-enclosed seas and coastal bodies have formed seasonal hypoxic water masses over large areas. The dominant cause for such formations is believed to be the increasing inflow of nutrients from watersheds and urban areas into estuaries and coastal waters. Several studies have reported...

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Bibliographic Details
Published in:Marine pollution bulletin 2020-02, Vol.151, p.110814-110814, Article 110814
Main Authors: Li, Xiuqin, Lu, Chuqian, Zhang, Yafeng, Zhao, Huade, Wang, Juying, Liu, Hongbin, Yin, Kedong
Format: Article
Language:English
Subjects:
Brackishwater environment
China
Coastal waters
Dissolved oxygen
Ecosystem
Environmental Monitoring
Estuaries
Estuarine dynamics
Hypoxia
Inflow
Nutrients
Oceans and Seas
Oxygen - analysis
Pearl River estuary
Regulating factors
Residence time
Residence time distribution
Rivers
Seasons
Semi-enclosed seas
Sewage
Stratification
Summer
Topography
Turbidity
Upstream
Urban areas
Variability
Vertical mixing
Water circulation
Water column
Water masses
Water stratification
Watersheds
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Summary:Several large semi-enclosed seas and coastal bodies have formed seasonal hypoxic water masses over large areas. The dominant cause for such formations is believed to be the increasing inflow of nutrients from watersheds and urban areas into estuaries and coastal waters. Several studies have reported hypoxic events in the Pearl River estuary (PRE). However, hypoxia events appear to be episodic, which are neither seasonal nor estuary-wide. The reasons for such occurrences are not understood fully. The objectives of this study are to use 24-year time series data obtained during 1988–2011 to analyze the long-term variability in dissolved oxygen (DO) in summer over the entire estuary from urban areas to estuarine coastal waters and examine regulating factors for the occurrences of hypoxia. The results showed that various regulating factors were responsible for the variability of DO in different regions of the PRE. DO decreased in the urban reach, upstream and main estuarine zones of the PRE from about 2000. It was hypoxic (DO
ISSN:0025-326X
1879-3363
DOI:10.1016/j.marpolbul.2019.110814