scholarly journals Seasonal Variation of Dissolved Oxygen in the Southeast of the Pearl River Estuary

Water ◽  
2020 ◽  
Vol 12 (9) ◽  
pp. 2475
Author(s):  
Guangping Liu ◽  
Weihong He ◽  
Shuqun Cai
Keyword(s):  
Dissolved Oxygen ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Empirical Orthogonal Functions ◽  
Pearl River ◽  
The Pearl River Estuary ◽  
Main Period ◽  
Do Concentration ◽  
The Pearl River ◽  
Bottom Hypoxia

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.

scholarly journals A numerical analysis of biogeochemical controls with physical modulation on hypoxia during summer in the Pearl River estuary

2017 ◽  
Vol 14 (12) ◽  
pp. 2979-2999 ◽  
Author(s):  
Bin Wang ◽  
Jiatang Hu ◽  
Shiyu Li ◽  
Dehong Liu
Keyword(s):  
River Estuary ◽  
Pearl River Estuary ◽  
Modulation Method ◽  
Pearl River ◽  
The West ◽  
The Pearl River Estuary ◽  
Hypoxic Area ◽  
The Pearl River ◽  
Bottom Hypoxia ◽  
Source And Sink

Abstract. A three-dimensional (3-D) physical–biogeochemical coupled model was applied to explore the mechanisms controlling the dissolved oxygen (DO) dynamics and bottom hypoxia during summer in the Pearl River estuary (PRE). By using the numerical oxygen tracers, we proposed a new method (namely the physical modulation method) to quantify the contributions of boundary conditions and each source and sink process occurring in local and adjacent waters to the DO conditions. A mass balance analysis of DO based on the physical modulation method indicated that the DO conditions at the bottom layer were mainly controlled by the source and sink processes, among which the sediment oxygen demand (SOD) at the water–sediment interface and the re-aeration at the air–sea interface were the two primary processes determining the spatial extent and duration of bottom hypoxia in the PRE. The SOD could cause a significant decrease in the bottom DO concentrations (averaged over July–August 2006) by over 4 mg L−1 on the shelf off the Modaomen sub-estuary, leading to the formation of a high-frequency zone of hypoxia (HFZ). However, the hypoxia that occurred in the HFZ was intermittent and distributed in a small area due to the combined effects of re-aeration and photosynthesis, which behaved as sources for DO and offset a portion of the DO consumed by SOD. The bottom DO concentrations to the west of the lower Lingdingyang Bay (i.e. the western shoal near Qi'ao Island) were also largely affected by high SOD, but there was no hypoxia occurring there because of the influence of re-aeration. Specifically, re-aeration could lead to an increase in the bottom DO concentrations by ∼ 4.8 mg L−1 to the west of the lower Lingdingyang Bay. The re-aeration led to a strong vertical DO gradient between the surface and the lower layers. As a result, the majority (∼ 89 %) of DO supplemented by re-aeration was transported to the lower layers through vertical diffusion and ∼ 28 % reached the bottom eventually. Additional numerical experiments showed that turning off re-aeration could lead to an expansion of the hypoxic area from 237 to 2203 km2 and result in persistent hypoxia (hypoxic frequency  >  80 %) to the west of the lower Lingdingyang Bay. Compared to re-aeration and SOD, photosynthesis and water column respiration had relatively small impacts on the DO conditions; turning off these two processes increased the hypoxic area to 591 km2. In summary, our study explicitly elucidated the interactive impacts of physical and biogeochemical processes on the DO dynamics in the PRE, which is critical to understanding hypoxia in this shallow and river-dominated estuarine system.

scholarly journals Destruction and reinstatement of coastal hypoxia in the South China Sea off the Pearl River Estuary

2020 ◽  
Author(s):  
Yangyang Zhao ◽  
Khanittha Uthaipan ◽  
Zhongming Lu ◽  
Yan Li ◽  
Jing Liu ◽  
...  
Keyword(s):  
South China Sea ◽  
Intermittent Hypoxia ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Pearl River ◽  
The Pearl River Estuary ◽  
Hypoxic Conditions ◽  
Bottom Waters ◽  
Do Concentration ◽  
The Pearl River

Abstract. We examined the evolution of intermittent hypoxia off the Pearl River Estuary during three cruise legs conducted in July 2018: one during severe hypoxic conditions before the passage of a typhoon and two post-typhoon legs showing destruction of the hypoxia and its reinstatement. The lowest ever regional dissolved oxygen (DO) concentration of 3.5 μmol kg−1 (~ 0.1 mg L−1) was observed in bottom waters during Leg 1, with a ~ 660 km2 area experiencing hypoxic conditions (DO 

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

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

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

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.

Morphology and bloom dynamics of Cochlodinium geminatum (Schütt) Schütt in the Pearl River Estuary, South China Sea

Harmful Algae ◽  
2012 ◽  
Vol 13 ◽  
pp. 10-19 ◽  
Author(s):  
Ping-Ping Shen ◽  
Ya-Nan Li ◽  
Yu-Zao Qi ◽  
Lv-Ping Zhang ◽  
Ye-Hui Tan ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
River Estuary ◽  
Pearl River Estuary ◽  
Pearl River ◽  
China Sea ◽  
The Pearl River Estuary ◽  
The Pearl River
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