Dataset Information

Encountering shoaling internal waves on the dispersal pathway of the pearl river plume in summer.

ABSTRACT: Fundamentally, river plume dynamics are controlled by the buoyancy due to river effluent and mixing induced by local forcing such as winds and tides. Rarely the influence of far-field internal waves on the river plume dynamics is documented. Our 5-day fix-point measurements and underway acoustic profiling identified hydrodynamic processes on the dispersal pathway of the Pearl River plume. The river plume dispersal was driven by the SW monsoon winds that induced the intrusion of cold water near the bottom. The river effluent occupied the surface water, creating strong stratification and showing on-offshore variability due to tidal fluctuations. However, intermittent disruptions weakened stratification due to wind mixing and perturbations by nonlinear internal waves (NIWs) from the northern South China Sea (NSCS). During events of NIW encounter, significant drawdowns of the river plume up to 20 m occurred. The EOF deciphers and ranks the contributions of abovementioned processes: (1) the stratification/mixing coupled by wind-driven plume water and NIWs disruptions (81.7%); (2) the variation caused by tidal modulation (6.9%); and (3) the cold water intrusion induced by summer monsoon winds (5.1%). Our findings further improve the understanding of the Pearl River plume dynamics influenced by the NIWs from the NSCS.

SUBMITTER: Lee J

PROVIDER: S-EPMC7807090 | biostudies-literature | 2021 Jan

REPOSITORIES: biostudies-literature

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Encountering shoaling internal waves on the dispersal pathway of the pearl river plume in summer.

Lee Jay J Liu James T JT Lee I-Huan IH Fu Ke-Hsien KH Yang Rick J RJ Gong Wenping W Gan Jianping J

Scientific reports 20210113 1

Fundamentally, river plume dynamics are controlled by the buoyancy due to river effluent and mixing induced by local forcing such as winds and tides. Rarely the influence of far-field internal waves on the river plume dynamics is documented. Our 5-day fix-point measurements and underway acoustic profiling identified hydrodynamic processes on the dispersal pathway of the Pearl River plume. The river plume dispersal was driven by the SW monsoon winds that induced the intrusion of cold water near t ...[more]

PMID: 33441816

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Project description:In recent decades, hypoxic areas have rapidly expanded worldwide in estuaries and coastal zones. The Pearl River Estuary (PRE), one of China's largest estuaries, experiences frequent seasonal hypoxia due to intense human activities and eutrophication. However, the ecological effects of hypoxia in the PRE, particularly on fish communities, remain unclear. To explore these effects, we collected fish community and environmental data in July 2021 during the summer hypoxia development period. The results revealed that bottom-layer dissolved oxygen (DO) in the PRE ranged from 0.08 to 5.71 mg/L, with extensive hypoxic zones (DO ≤ 2 mg/L) observed. Hypoxia has varied effects on fish community composition, distribution, species, and functional diversity in the PRE. A total of 104 fish species were collected in this study, with approximately 30 species (28.6%) exclusively found in hypoxic areas. Species responses to hypoxia varied: species such as Sardinella zunasi, Coilia mystus, and Nuchequula nuchalis were sensitive, while Decapterus maruadsi, Siganus fuscescens, and Lagocephalus spadiceus showed higher tolerance. Within the hypoxia area, dissolved oxygen was the main limiting factor for fish community diversity. Functional diversity (FDiv) decreased with higher dissolved oxygen levels, indicating a potential shift in the functional traits and ecological roles of fish species in response to changing oxygen conditions. Further analysis demonstrated that dissolved oxygen had a significantly stronger effect on fish community structure at hypoxic sites than in the whole PRE. Moreover, other environmental variables also had significant effects on the fish community structure and interacted with dissolved oxygen in the hypoxia area. These findings suggest that maintaining sufficient dissolved oxygen levels is essential for sustaining fish communities and ecosystem health in the PRE. This study provides novel insights into the effects of hypoxia on fish communities in estuarine ecosystems and has significant implications for the ecological health and management of the PRE.

Dataset Information

Encountering shoaling internal waves on the dispersal pathway of the pearl river plume in summer.

Publications

Encountering shoaling internal waves on the dispersal pathway of the pearl river plume in summer.

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