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Coastal water quality and trophic status are subject to intensive environmental stress induced by human activities and climate change. Quarterly cruises were conducted to identify environmental characteristics in Daya Bay in 2013. Water quality is spatially and temporally dynamic in the bay. Cluster analysis (CA) groups 12 monitoring stations into two clusters. Cluster I consists of stations (S1, S2, S4–S7, S9, and S12) located in the central, eastern, and southern parts of the bay, representing less polluted regions. Cluster II includes stations (S3, S8, S10, and S11) located in the western and northern parts of the bay, indicating the highly polluted regions receiving a high amount of wastewater and freshwater discharge. Principal component analysis (PCA) identified that water quality experience seasonal change (summer, winter, and spring–autumn seasons) because of two monsoons in the study area. Eutrophication in the bay is graded as high by Assessment of Estuarine Trophic Status (ASSETS). [ABSTRACT FROM AUTHOR]

Environmental changes driven by intense human disturbance and natural processes govern the abundance and distribution characteristics of two picophytoplankton groups (Synechococcus and picoeukaryotes). Picophytoplancton and high DNA (HDNA) and low DNA (LDNA) bacterial groups, identified by flow cytometry, were assessed during the autumn monsoon transition period in Daya Bay (South China Sea). The abundance of Synechococcus and picoeukaryotes ranged from 2.16 x 104 to 1.45 x 105 cell mL-1 and from 0.78 x 10³ to 7.95 x 10³ cell mL-1, respectively. The abundance of HDNA bacteria in surface water (mean: 5.58 x 105 cell mL-1) was greater than in bottom water (mean: 3.74 x 105 cell mL-1), with significant difference (n = 12, P = 0.05). The difference in LDNA abundances between surface (mean: 7.06 x 105 cell mL-1) and bottom (mean: 4.83 x 105 cell mL-1) waters was insignificant (n = 12, P > 0.05). The results of the principal component analysis showed that both picophytoplankton (Synechococcus and picoeukaryotes) and bacteria (HDNA and LDNA) were positively related to nutrients (NO3-N, NH4-N, and SiO3-Si). Three subsystems in the bay were identified as follows: the west and east parts, the central and northwest parts, and the mouth and central part. [ABSTRACT FROM AUTHOR]

The article discusses a study which aimed to identify environmental factors affecting phytoplankton structure in Daya Bay, South China Sea. It found that temperature and nutrient ratios are the factors driving phytoplankton succession in the bay. The role played by hydrodynamic processes in phytoplankton growth is noted. Also mentioned are diatoms which are the dominant species in the bay, including Chaetoceros affinis, Chaetoceros lorenzianus, and Nitzschia pungens.

Eleven physicochemical parameters of data collected from 12 stations in Daya Bay in 2003 were analyzed by multivariate statistical analysis. Cluster analysis (CA) grouped data from 4 seasons into two groups, the northeast and southwest monsoon periods, representing different natural processes. During the northeast monsoon period, principal component analysis (PCA) and CA group the 12 monitoring sites into Cluster DA1 (S1, S2 and S6) and Cluster DA2 (S3-S5 and S7-S12). During the southwest monsoon period, PCA and CA group the 12 monitoring sites into Cluster WB1 (S1, S2, S7, S9 and S11) and Cluster WB2 (S3-S6, S8, S10, S11 and S12). The spatial heterogeneity within the bay was defined by different hydrodynamic conditions and human activities. These results may be valuable for achieving sustainable use of the coastal ecosystems in Daya Bay. [ABSTRACT FROM AUTHOR]

The coastal ecosystem in the Daya Bay is sensitive to the environmental changes induced by highly intensive human activities. We obtained and compiled the recent 30 years' field observational data on nutrients and phytoplankton communities to explore the changing ecosystem. Dissolved inorganic nitrogen concentration (DIN) has significantly increased, while phosphate concentration (DIP) dramatically decreased because of costal anthropogenic influence. The limited factors for phytoplankton have changed from nitrogen in the 1980s to phosphate in the mid-1990s. The net-collected phytoplankton communities has the miniaturized trend, while there is drastic increase of Chlorophyll a (Chl- a ) concentration. Even though the diatoms still dominate in phytoplankton community, the dominant species have slightly changed. The alga bloom greatly changed from diatoms dominated to dinoflagellates due to changes of nutrient structure. All these changes on nutrients and phytoplankton communities appear to be closely associated with human activities along the coast of the Daya Bay. [ABSTRACT FROM AUTHOR]