Subsurface low dissolved oxygen occurred at fresh- and saline-water intersection of the Pearl River estuary during the summer period

Dissolved oxygen (DO) concentration in estuaries is highly variable at different spatial and temporal scales, which is affected by physical, chemical and biological processes. This study analyzed the spatial–temporal distributions of dissolved oxygen concentration and bottom hypoxia in the southeast of the Pearl River Estuary (PRE) using monthly water quality monitoring and hydrographic data covering the period 2000–2017. The seasonal spatial–temporal variation of DO concentration was studied using various methods, such as rotated empirical orthogonal functions, harmonic analysis, and correlation analysis. The results showed that DO stratification was significant in summer, but it was not distinct in winter, during which DO concentration peaked. DO stratification exhibited a significantly positive correlation with water stratification. In the south and west of Hong Kong (SHK and WHK, respectively), DO concentration fields exhibited distinct seasonal changes in the recent 18 years. In SHK, the main periods of the surface DO variation were 24, 12, and 6 months, whereas the main period was 12 months in WHK. The main period of the bottom DO variation was 12 months in both SHK and WHK. In SHK, the spatial–temporal variations in surface and bottom DO were highly related to the variations of salinity, dissolved inorganic nitrogen (DIN), and active phosphorus, and the variation of surface DO was also connected to the variation of temperature and chlorophyll a. In WHK, the variations in surface and bottom DO were highly related to the variations of salinity and temperature, and the variation of surface DO was also connected to the variation of DIN. The river discharge and wind had a different important influence on the temporal variability of DO in WHK and SHK. These findings suggested that the variations of DO may be controlled by coupled physical and biochemical processes in the southeast of PRE. From 2000 to 2017, bottom hypoxia in the southeast of PRE occurred in the summers of 7 years. SHK appeared to be more vulnerable to hypoxia than WHK.

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Temporal and spatial distribution of dissolved oxygen in the Pearl River Estuary and adjacent coastal waters

Continental Shelf Research ◽

10.1016/j.csr.2004.06.017 ◽

2004 ◽

Vol 24 (16) ◽

pp. 1935-1948 ◽

Cited By ~ 108

Author(s):

Kedong Yin ◽

Zhifeng Lin ◽

Zhiyuan Ke

Keyword(s):

Spatial Distribution ◽

Dissolved Oxygen ◽

Coastal Waters ◽

River Estuary ◽

Pearl River Estuary ◽

Pearl River ◽

Temporal And Spatial Distribution ◽

The Pearl River Estuary ◽

Temporal And Spatial ◽

The Pearl River

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Picophytoplankton abundance and distribution in three contrasting periods in the Pearl River Estuary, South China

Marine and Freshwater Research ◽

10.1071/mf12303 ◽

2013 ◽

Vol 64 (8) ◽

pp. 692 ◽

Cited By ~ 8

Author(s):

Xia Zhang ◽

Zhen Shi ◽

Feng Ye ◽

Yanyi Zeng ◽

Xiaoping Huang

Keyword(s):

South China ◽

Saline Water ◽

Salinity Gradient ◽

River Estuary ◽

Pearl River Estuary ◽

Pearl River ◽

Spatial Gradient ◽

The Pearl River Estuary ◽

The Pearl River ◽

Abundance And Distribution

Abundance and distribution characteristics of three picophytoplankton groups (Synechococcus, Prochlorococcus and picoeukaryotes), identified by flow cytometer, and two types of picocyanobacteria (phycoerythrin and phycocyanin-rich strains), determined by epifluorescence microscope, were assessed in three contrasting periods in the Pearl River Estuary, South China. The average abundance of picophytoplankon and picocyanobacteria was 104 cells mL–1 in the two summer observations and 103 cells mL–1 in winter. Low cell density in the cold season was probably due to high turbidity and low water temperature. Prochlorococcus was detected within the estuarine plume in the summer investigations and was undetectable in the winter. Higher abundance and the further upstream occurrence of Prochlorococcus in the summer of 2011 were mainly associated with extreme low river flows. We presumed that Prochlorococcus abundance and distribution range were balanced by river discharge and saline-water intrusion. Synechococcus was the dominant group in the inner estuary. Similar to Prochlorococcus, Synechococcus distribution was related with freshwater inflow. The river inflow exerted strong limitation on Synechococcus and Prochlorococcus, with this effect weakening along the salinity gradient. Picoeukaryotes were the least abundant category among picophytoplankton and showed a different distribution pattern from that of Synechococcus and Prochlorococcus. For picocyanobacteria, there was a clear spatial gradient with phycocyanin-rich strains dominant in the upper estuary, and phycocyanin-rich and phycoerythrin-rich cells dominant downstream. A significant negative correlation was observed between phycocyanin-rich cells to phycoerythrin-rich cells ratio and salinity.

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Effects of climate change and fishing on the Pearl River Estuary ecosystem and fisheries

Reviews in Fish Biology and Fisheries ◽

10.1007/s11160-019-09574-y ◽

2019 ◽

Vol 29 (4) ◽

pp. 861-875

Author(s):

Zeyu Zeng ◽

William W. L. Cheung ◽

Shiyu Li ◽

Jiatang Hu ◽

Ying Wang

Keyword(s):

Climate Change ◽

River Estuary ◽

Pearl River Estuary ◽

Pearl River ◽

The Pearl River Estuary ◽

The Pearl River

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The Role of Environmental Factors on the Fishery Catch of the Squid Uroteuthis chinensis in the Pearl River Estuary, China

Journal of Marine Science and Engineering ◽

10.3390/jmse9020131 ◽

2021 ◽

Vol 9 (2) ◽

pp. 131

Author(s):

Dongliang Wang ◽

Lijun Yao ◽

Jing Yu ◽

Pimao Chen

Keyword(s):

River Estuary ◽

Pearl River Estuary ◽

Sea Surface ◽

Spatiotemporal Variability ◽

Pearl River ◽

Coastal Current ◽

Catch Per Unit Effort ◽

Chl A ◽

The Pearl River Estuary ◽

The Pearl River

The Pearl River Estuary (PRE) is one of the major fishing grounds for the squid Uroteuthis chinensis. Taking that into consideration, this study analyzes the environmental effects on the spatiotemporal variability of U. chinensis in the PRE, on the basis of the Generalized Additive Model (GAM) and Clustering Fishing Tactics (CFT), using satellite and in situ observations. Results show that 63.1% of the total variation in U. chinensis Catch Per Unit Effort (CPUE) in the PRE could be explained by looking into outside factors. The most important one was the interaction of sea surface temperature (SST) and month, with a contribution of 26.7%, followed by the interaction effect of depth and month, fishermen’s fishing tactics, sea surface salinity (SSS), chlorophyll a concentration (Chl a), and year, with contributions of 12.8%, 8.5%, 7.7%, 4.0%, and 3.1%, respectively. In summary, U. chinensis in the PRE was mainly distributed over areas with an SST of 22–29 °C, SSS of 32.5–34‰, Chl a of 0–0.3 mg × m−3, and water depth of 40–140 m. The distribution of U. chinensis in the PRE was affected by the western Guangdong coastal current, distribution of marine primary productivity, and variation of habitat conditions. Lower stock of U. chinensis in the PRE was connected with La Niña in 2008.

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