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Physicochemical and benthos data were collected from 12 marine monitoring stations in Daya Bay, during 2001-2004. 12 stations in Daya Bay could be grouped into three clusters: cluster I consisted of stations in the southern part of Daya Bay (stations S1, S2 and S6); cluster II consisted of stations in the cage culture areas (stations S3, S4, S5 and S8); cluster III consisted of stations in the southwest, the middle and the northeast of the Bay (stations S7, S9, S10, S11 and S12). Calculation with bivariate correlations between benthos and major physicochemical factors showed that the density of benthos in all stations correlated positively with temperature, DO, pH, NH-N, SiO-Si, SiO-Si /PO-P and chlorophyll a and was negatively correlated with salinity, Secchi, COD, NO-N, NO-N, TIN, PO-P, TIN/PO-P and BOD. Factor analysis showed that there were high positive loading salinity, Secchi and NH-N of three clusters. Results revealed that temperature, DO, pH, SiO-Si and SiO-Si/PO-P and chlorophyll a could also play an important role in determining the biomass of benthos in Daya Bay, especially near the Nuclear Power Plants, in the southern part and in the cage culture areas. [ABSTRACT FROM AUTHOR]

In this study, the effect of multiple heavy metal stress on ascorbate (AsA), glutathione (GSH) and related enzymes was investigated in the leaves, stems and roots of Kandelia candel and Bruguiera gymnorrhiza. Mangrove seedlings were treated with five different concentrations of a heavy metal mixture (Cd2+, Pb2+ and Hg2+). Antioxidants in both the species were analyzed after one month. AsA, GSH, ascorbate peroxidase (APX, EC 1.11.1.11) and glutathione reductase (GR, EC 1.6.4.2) exhibited a similar trend with initial increase and subsequent decrease in response to heavy metal stress. At the highest metal concentration, a significant decrease of AsA and GR was observed in K. candel and B. gymnorrhiza. Glutathione peroxidase (GPX, EC 1.11.1.9) in the leaves, stems and roots of K. candel reached their respective maximal values at the highest metal concentration, whereas GPX activity in roots and stems of B. gymnorrhiza was similar to the controls at higher metal concentrations. Our results demonstrate that AsA, GSH, APX, GR and GPX in K. candel may play more important roles in defending against reactive oxygen species (ROS) than those in B. gymnorrhiza. [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]

Vertical variations of bacterial community composition in the South China Sea was investigated on 18 September 2009 by denaturing gradient gel electrophoresis (DGGE) and analyzed by multivariate analysis. Twenty-seven sequences retrieved from DGGE bands fell into five groups based on BLAST analysis. The dominant bacteria were Cyanobacteria (35.7%) and Proteobacteria (39.2%). The DGGE profile showed Proteobacteria mostly obtained from samples from the deeper layers while sequences related to Cyanobacteria only existed in the euphotic layer. Other phylogenetic groups have been identi?ed as Firmicutes (10.7%), Actinobacteria (7.1%), and Deinococcus-Thermus (3.6%). The unweighted pair group method with arithmetic mean has been employed to cluster the samples, and results indicated that all samples tended to group together on the basis of depth and could be further subclassified into two subgroups: Group I (including samples from 0 m, 50 m, 75 m, 100 m, and 150 m) and Group II (including samples from 200 m, 400 m, 500 m, 600 m, 700 m, and 900 m). Canonical correspondence analysis revealed the temperature was the most significant factor in determining the vertical distribution of the bacterial community (P=0.018, P<0.05). [ABSTRACT FROM AUTHOR]

Human activities and natural processes like mixing and/or upwelling driven by climate change have a strong influence on water quality in the coastal regions. Human activities are the dominant factor for water quality in the mouth of the Sanya River. This region exhibited the maximum influence of discharge from the Saya estimated by higher nutrient levels and chlorophyll a (Chl a). Natural processes are the dominant factor regarding water quality in outer bay. Both human activities and natural processes play important roles on water quality in Sanya Bay. Each hydrologic and ecological zone has a specific water quality response associated with the relative importance of both human activities and natural processes. Therefore, the information would be useful for regional agencies in developing a strategy to carry out scientific plans for resource use based on marine system functions. [ABSTRACT FROM AUTHOR]