Abstract
A physical–biological ocean model was employed to investigate characteristics of the Beibu Gulf in the northwest South China Sea (SCS) from 2011 to 2015. We adopted the spatially constrained multivariate clustering method to determine the refined marine environmental regionalization using 10 variables from the model output, and compared regionalization differences in ENSO (El Niño–Southern Oscillation) years. The simulated physical and biochemical variables display a wide spectrum of patterns in space and time. The regionalization maps indicated that the Qiongzhou Strait and its adjacent area can be classified as a separate region, characterized by the rich presence of nutrients, phytoplankton, zooplankton, and detritus, owing to the water invasion from the western Guangdong estuary. As a result of the invasive progression of the SCS, the northern and southern gulf show distinct features over a boundary near 20° N. In the La Niña year (2011), the classified boundary of the Qiongzhou Strait-northeastern gulf moved southwards due to enhanced phytoplankton growth. In the El Niño year (2015), the current collision from the northern gulf and SCS resulted in the boundary of the northern and southern gulf moving to approximately 19° N. These results provide useful guidance on subregional marine management and subregional studies for the gulf.
Highlights
Biogeographic classification and regionalization are critical for developing ecologically representative systems of protected areas
The distribution of the SAL was strongly affected by the nutrient water from the western Guangdong estuaries through the Qiongzhou Strait and current [43], and had most significant difference here, it resulted in the boundary of river inputs from the Guangxi coast, while the southern gulf is mainly influenced by the the northern and the southern gulf moving to here
This can be model output as parameters, and applied an unsupervised machine learning clustering identified as an individual region, which represents the influence of the river method to regionalize the upper, middle, and bottom layers of the Beibu Gulf. inputs
Summary
Biogeographic classification and regionalization are critical for developing ecologically representative systems of protected areas. A knowledge of marine regionalization gives insights into climate change research, marine ecosystem protection policies, management of fisheries, and analyses of global food and environmental security [3,4,6]. Most marine regionalizations depend on representative oceanographic and biogeochemical features, such as sea surface temperature (SST), ocean circulation, bathymetry, and sea surface chlorophyll-a (Chl-a) [7,11,12]. Compared to global oceanic regionalization, regional marine regionalization can integrate physical and biochemical factors with a finer resolution, providing detailed information for marine ecological policies and management. Regional marine regionalization is commonly implemented on the scale of gulfs [3]
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