Abstract
Phytoplankton dynamics, which are highly sensitive to the ecosystem condition and change, are different in coastal waters and open ocean. Previous researches mainly focused on the open ocean dynamic in the South China Sea (SCS), but few research on the Eastern Guangdong (EGD), especially during a period of downwelling-favorable winds. In fact, the influence of topographic irregularities, downwelling, continental outflows, and cold, nutrient-rich currents from Fujian-Zhejiang coastal waters (ZFC) of the East China Sea (ECS) on the spatial distribution of Chlorophyll a (Chl a) in EGD coastal waters could be significant. This study utilized ocean color time series and meteorological and hydrographic data jointly from July 2002 to June 2020 to investigate the heterogeneous regional specific distribution pattern of Chl a in EGD and the environmental determinants in different regions subdivided by water depth. Then the temporal and spatial distribution pattern of Chl a in EGD in winter were discussed in detail by applying an Empirical Orthogonal Function (EOF) analysis, GaoFeng-1 (GF-1) satellite data and in situ measured dataset. The sea surface temperature (SST) in February was negatively related with Chl a in shallow coastal waters less than 60 m deep due to the nutrient-rich, cold waters from ZFC. The monthly mean photosynthetically active radiation (PAR) and precipitation showed significant effects on the phytoplankton growth over regions with a depth less than 10 m. An area with higher Chl a concentration in the downwelling zone were detected in winter. By an examining the temporal variability in meridional distribution of the mean Chl a at 22.41°N and 22.21°N, a symmetrical peak was observed. The coastal fronts extended southwestward from the southeastern coast of Guangdong Province to Dangan Island in the SCS. In addition, a cross-shelf filament was detected near the coast of Shanwei, Guangdong, China on 8 January 2020.
Highlights
Introduction published maps and institutional affilThe South China Sea (SCS) circulation are mainly driven by the East Asian Monsoon [1].The oceanographic studies on the SCS have been centered on the open ocean dynamic, the summer upwelling phenomena or the interaction between the Pearl River plume and the coastal current for a few decades [2–4]
Xi is the value of the ithwidely point in the data set, and mean value of the data set, n is thealso number of data points in the sure the model can be applied todata ourset.research area, we evaluate it by using i data collected in SCS (Figure 1)
Conclusions results showed chlorophyll a (Chl a) in region I in the Eastern Guangdong (EGD) coastal waters was highest in summer
Summary
Introduction published maps and institutional affilThe South China Sea (SCS) circulation are mainly driven by the East Asian Monsoon [1].The oceanographic studies on the SCS have been centered on the open ocean dynamic, the summer upwelling phenomena or the interaction between the Pearl River plume and the coastal current for a few decades [2–4]. The South China Sea (SCS) circulation are mainly driven by the East Asian Monsoon [1]. Liu [5] developed a three-dimensional numerical model with coupled physics and biogeochemistry to illustrate the relationship between the nutrient upwelling and phytoplankton growth in the SCS. Chen [6] discussed the effects of upwelling on the phytoplankton blooms in the SCS. Zhang [7] examined the variability of chlorophyll a (Chl a) in the open SCS by using observations from two Bio-Argo floats. He [8] analyzed the influence of the intense mesoscale eddies on Chl a in summer in the western South China Sea (WSCS) in summer by using historical in situ observations, satellite-derived Chl a and eddy data.
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