Cui-Ci Sun

Ecological environment changes in Daya Bay, China, from 1982 to 2004

Data collected from 12 marine monitoring stations in Daya Bay from 1982 to 2004 reveal a substantial change in the ecological environment of this region. The average N/P ratio increased from 1.377 in 1985 to 49.09 in 2004. Algal species changed from 159 species of 46 genera in 1982 to 126 species of 44 genera in 2004. Major zooplankton species went from 46 species in 1983 to 36 species in 2004. The annual mean biomass of benthic animals was recorded at 123.10 g m(-2) in 1982 and 126.68 g m(-2) in 2004. Mean biomass and species of benthic animals near nuclear power plants ranged from 317.9 g m(-2) in 1991 to 45.24 g m(-2) in 2004 and from 250 species in 1991 to 177 species in 2004. A total of 12-19 species of hermatypic corals and 13 species of mangrove plants were observed in Daya Bay from 1984 to 2002.

Identification of coastal water quality by statistical analysis methods in Daya Bay, South China Sea.

In this paper, cluster analysis (CA), principal component analysis (PCA) and the fuzzy logic approach were employed to evaluate the trophic status of water quality for 12 monitoring stations in Daya Bay in 2003. CA grouped the four seasons into four groups (winter, spring, summer and autumn) and the sampling sites into two groups (cluster DA: S1, S2, S4-S7, S9 and S12 and cluster DB: S3, S8, S10 and S11). PCA identified the temporal and spatial characteristics of trophic status in Daya Bay. Cluster DB, with higher concentrations of TP and DIN, is located in the western and northern parts of Daya Bay. Cluster DA, with the low Secchi, is located in the southern and eastern parts of Daya Bay. The fuzzy logic approach revealed more information about the temporal and spatial patterns of the trophic status of water quality. Chlorophyll a, TP and Secchi may be major factors for deteriorating water quality.

Identification of anthropogenic effects and seasonality on water quality in Daya Bay, South China Sea.

Thirteen water quality parameters from 12 monitoring stations were collected to study the effects caused by climate and anthropogenic activities on water quality in 2003 in Daya Bay, South China Sea. The data matrix has been built according to the results, which were analyzed by fuzzy c-mean cluster (FCM) and cluster analysis (CA). This analysis has identified anthropogenic effects and seasonal characters of water quality. The dry and wet seasonality have been demonstrated with FCM and CA. The precipitation and the Southeast Asian monsoons, northeasterly from October to the next April and southwesterly from May to September have also an important influence on water quality in Daya Bay. In the spatial pattern, two groups have been classified with FCM and CA. Cluster I consisted of the sites S3, S8, S10 and S11 in the west and north coastal parts of Daya Bay. Cluster I is mainly related to anthropogenic activities such as fish-farming. Cluster II consisted of the rest of the stations in the center, east and south parts of Daya Bay. Cluster II is mainly related to seawater input from South China Sea. Thus, fuzzy c-mean cluster and cluster analysis can be an important tool for the successful characterization of regional-scale water quality.

The effect of multiple heavy metals on ascorbate, glutathione and related enzymes in two mangrove plant seedlings [Kandelia candel and Bruguiera gymnorrhiza]

The effect of multiple heavy metals on ascorbate, glutathione and related enzymes in two mangrove plant seedlings (Kandelia candel and Bruguiera gymnorrhiza) 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.

Seasonal Variation of Water Quality and Phytoplankton Response Patterns in Daya Bay, China

Data collected from 12 stations in Daya Bay in different seasons in 2002 revealed the relation between water quality and phytoplankton response patterns. The results showed that Daya Bay could be divided into wet and dry seasons by multivariate statistical analysis. Principal component analysis indicated that temperature, chlorophyll a and nutrients were important components during the wet season (summer and autumn). The salinity and dissolved oxygen were the main environmental factors in the dry season (winter and spring). According to non-metric multidimensional scaling, there was a shift from the large diatoms in the dry season to the smaller line-chain taxa in the wet season with the condition of a high dissolved inorganic nitrogen and nitrogen to phosphorous concentration ratio. Nutrient changes can thus alter the phytoplankton community composition and biomass, especially near the aquaculture farm areas. There was no evidence of an effect of thermal water from the nearby nuclear power plants on the observed changes in phytoplankton community and biomass in 2002.

Characterization and expression analysis of three CBF/DREB1 transcriptional factor genes from mangrove Avicennia marina

Three CBF/DREB1 (C-repeat binding factor/dehydration responsive element-binding factor 1) homologues were isolated from mangrove Avicennia marina and designated AmCBF1, 2 and 3. Multiple sequence analysis showed that the three deduced proteins all contain an AP2 DNA-binding domain and two CBF signature sequences. According to the phylogenetic analysis, these proteins belong to the A-1 subgroup of the DREB subfamily. Expression analyses based on quantitative real-time PCR revealed that the AmCBF2 displayed relatively high expression under normal conditions, with the highest level in stems, while both AmCBF1 and 3 were weakly expressed without stress. The three genes also showed different responses to various environmental stimuli. The AmCBF2 was inducible by cold, drought, high salinity, heavy metals, as well as abscisic acid (ABA), and exhibited much stronger induction by cold, drought, Pb(2+) or Zn(2+) than by NaCl, ABA or Cd(2+). In contrast, both AmCBF1 and AmCBF3 displayed insignificant changes under these stimuli. These results indicate that the three AmCBF genes play different roles in A. marina and the AmCBF2 might be involved in the signaling pathway of cold, drought and heavy metal stress response.

Effects of pyrene on antioxidant systems and lipid peroxidation level in mangrove plants, Bruguiera gymnorrhiza

The effects of polycyclic aromatic hydrocarbon (PAH) (pyrene) on superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase, peroxidase, malondialdehyde (MDA) and proline were studied in leaves, stems and roots of Bruguiera gymnorrhiza. The results showed that the responses of enzymatic and non-enzymatic antioxidants varied significantly among the three tissues studied. The activities of antioxidant enzymes in PAH-treated stems and roots fluctuated in different stress levels compared to the controls, while the antioxidant enzymes such as SOD, APX in leaves increased when stressed by PAH with a significant positive relation between PAH and leaf SOD or APX activity. Low PAH treatments could also stimulate proline in leaves and stems. MDA content was obviously accumulated in stems and roots under PAH stress while decreased in leaves, indicating that the increased antioxidant enzymes in leaves may partly alleviate lipid peroxidation. For pollution monitoring purpose, SOD and APX in leaves may be potential biomarkers of PAH pollution in intertidal estuaries.

Effects of polycyclic aromatic hydrocarbons exposure on antioxidant system activities and proline content in Kandelia candel

The antioxidant system effects of Kandelia candel were investigated under four different levels of PAH stress. The activities of antioxidant enzymes including superoxide dismutase (SOD), catalase (CAT) and peroxidase (POD), the responses to the change of malondialdehyde (MDA) contents and the accumulation of proline in K. candel were determined. Our results suggested that the activities of SOD, CAT, POD increased significantly in leaves and roots of K. candel (p≤0.05) with the increase of the external PAH concentrations, while in stems, the activities of these antioxidant enzymes were all significantly inhibited (p≤0.01). We also observed an increase of MDA in leaves, stems and roots, and an obvious correlation between MDA content and PAH concentrations in three locations, which showed that the change of MDA content could be used as a biomarker of K. candel under PAH stress. The proline content was found remarkably enhanced in leaves, stems and roots. However, a significant inverse correlation was observed between the proline content and SOD (r=−0.99, p≤0.01), POD (r=−0.95, p≤0.05) activities in stems. This study suggested that the antioxidative system of K. candel has an obvious organ-dependent feature when exposed to PAH contamination as revealed by discriminant analysis (DA).

Metal (Pb, Zn and Cu) uptake and tolerance by mangroves in relation to root anatomy and lignification/suberization

Metal pollution has been widely reported in mangrove wetlands; however, the mechanisms involved in metal detoxification by mangroves are still poorly understood. This study aimed to investigate the possible function of root anatomy and lignification/suberization on metal uptake and tolerance in seedlings of six species of mangroves. The results revealed that the three rhizophoraceous species (Bruguiera gymnorrhiza (L.) Poir, Kandelia obovata Sheue, Liu & Yong and Rhizophora stylosa Griff) consistently exhibited higher metal tolerances than the three pioneer species (Aegiceras corniculatum (Linn.) Blanco, Acanthus ilicifolius L. and Avicennia marina (Forsk.) Viern.). Moreover, metal-tolerant species often exhibited a thick exodermis with high lignification and suberization. The tolerance indices of the mangroves were found to be positively correlated with the amounts of lignin and suberin deposition within the exodermal cell walls. The observed metal uptake by the excised roots further illustrated that a lignified/suberized exodermis directly delayed the entry of metals into the roots, and thereby contributed to a higher tolerance to heavy metals. In summary, the present study proposes a barrier property of the lignified/suberized exodermis in dealing with the stresses of heavy metals, such that the mangroves which possessed more extensive lignification/suberization within the exodermis appeared to exhibit higher metal tolerance.

Distribution characteristics of transparent exopolymer particles in the Pearl River estuary, China

Distribution of Transparent Exopolymer Particles (TEP) in the Pearl River estuary, China, was investigated during two cruises in August 2009 and January 2010. TEPcolor concentrations were 521.5-1727.4 mg Xeq.L-1 (mu g Gum Xanthan equivalent liter(-1)) in August 2009 and 88.7-1586.9 mu g Xeq.L-1 in January 2010, respectively. The size of TEP generally increased in the seaward along the longitudinal section with the dominant size of 2-40 mu m during the cruises. Experimental work suggested that both concentration and size of TEP increased with Ca2+ concentration (from 0.8 mmol L-1 to 10 mmol L-1). In the field study, Ca2+ concentration had a positive correlation with TEPcolor concentration in the surface layer with salinity <16. Decrease of TEP concentration seaward from intermediary salinity was partly due to dilution of seawater as well as enhanced aggregation and sedimentation of TEP via increasing divalent cation concentration. TEP concentration and turbidity maximum coexisted at the tip of salt wedge in the bottom layer during the wet season, and positive correlation between TEP and turbidity was observed in the winter. Relationships between TEP and turbidity suggested the important contribution of TEP aggregation to flocculation and sedimentation of particles in estuaries. Different pattern of TEP during two cruises can be attributed to physical process (i.e., mixing type) in estuaries. These findings indicated that formation and distribution of TEP were largely influenced by interaction between physical and biogeochemical processes in the Pearl River estuary. A conceptual model for TEP formation and distribution in the Pearl River estuary was developed. Citation: Sun, C.-C., Y.-S. Wang, Q. P. Li, W.-Z. Yue, Y.-T. Wang, F.-L. Sun, and Y.-L. Peng (2012), Distribution characteristics of transparent exopolymer particles in the Pearl River estuary, China, J. Geophys. Res., 117, G00N17, doi: 10.1029/2012JG001951.