Dependence of evolution of Cyanobacteria superiority on temperature and nutrient use efficiency in a meso-eutrophic plateau lake.

Algal blooms in lakes have been a challenging environmental issue globally under the dual influence of human activity and climate change. Considerable progress has been made in the study of phytoplankton dynamics in lakes; The long-term in situ evolution of dominant bloom-forming cyanobacteria in meso-eutrophic plateau lakes, however, lacks systematic research. Here, the monthly parameters from 12 sampling sites during the period of 1997-2022 were utilized to investigate the underlying mechanisms driving the superiority of bloom-forming cyanobacteria in Erhai, a representative meso-eutrophic plateau lake. The findings indicate that global warming will intensify the risk of cynaobacteria blooms, prolong Microcystis blooms in autumn to winter or even into the following year, and increase the superiority of filamentous Planktothrix and Cylindrospermum in summer and autumn. High RUETN (1.52 Biomass/TN, 0.95-3.04 times higher than other species) under N limitation (TN < 0.5 mg/L, TN/TP < 22.6) in the meso-eutrophic Lake Erhai facilitates the superiority of Dolichospermum. High RUETP (43.8 Biomass/TP, 2.1-10.2 times higher than others) in TP of 0.03-0.05 mg/L promotes the superiority of Planktothrix and Cylindrospermum. We provided a novel insight into the formation of Planktothrix and Cylindrospermum superiority in meso-eutrophic plateau lake with low TP (0.005-0.07 mg/L), which is mainly influenced by warming, high RUETP and their vertical migration characteristics. Therefore, we posit that although the obvious improvement of lake water quality is not directly proportional to the control efficacy of cyanobacterial blooms, the evolutionary shift in cyanobacteria population structure from Microcystis, which thrives under high nitrogen and phosphorus conditions, to filamentous cyanobacteria adapted to low nitrogen and phosphorus levels may serve as a significant indicator of water quality amelioration. Therefore, we suggest that the risk of filamentous cyanobacteria blooms in the meso-eutrophic plateau lake should be given attention, particularly in light of improving water quality and global warming, to ensure drinking water safety.

Helical Nanographenes Bearing Pentagon-Heptagon Pairs by Stepwise Dehydrocyclization.

The incorporation of pentagon-heptagon pairs into helical nanographenes lacks a facile synthetic route, and the impact of these pairs on chiroptical properties remains unclear. In this study, a method for the stepwise construction of pentagon-heptagon pairs in helical nanographenes by the dehydrogenation of [6]helicene units was developed. Three helical nanographenes containing pentagon-heptagon pairs were synthesized and characterized using this approach. A wide variation in the molecular geometries and photophysical properties of these helical nanographenes was observed, with changes in the helical length of these structures and the introduction of the pentagon-heptagon pairs. The embedded pentagon-heptagon pairs reduced the oxidation potential of the synthesized helical nanographenes. The high isomerization energy barriers enabled the chiral resolution of the helicene enantiomers. Chiroptical investigations revealed remarkably enhanced circularly polarized luminescence and luminescence dissymmetry factors with an increasing number of the pentagon-heptagon pairs.

Spatiotemporal dynamics of phytoplankton biomass and community succession for driving factors in a meso-eutrophic lake.

Effects of climate change and nutrient load caused by human activities on lake phytoplankton blooms have attracted much attention globally. However, their roles and synergistic effects on phytoplankton biomass and community historical succession are not well understood, especially for meso-eutrophic plateau lakes. In this study, a multi-year (1997-2022) monthly dataset including hydro-chemical and meteorological indicators of the meso-eutrophic plateau lake Erhai in China, was used to explore the contributions of climate change and nutrients on phytoplankton biomass variation and community succession. Phytoplankton biomass increased from 1997 to 2006, slowly decreased from 2006 to 2015, then increased again from 2015 to 2022, according to a generalised additive model (GAM). Alongside warming, nitrogen, phosphorus and organic matter are key drivers of long-term interannual variation in phytoplankton biomass and historical succession of the phytoplankton community. The extensive blooms in recent years were strongly associated with both organic matter accumulation and global warming. Phytoplankton biomass in northern and southern districts was greater than in central areas, with Cyanophyta and Pyrrophyta dominating in the north and Chlorophyta prevalent in the south. Since 2015, phytoplankton diversity has increased significantly, and biomass has declined in the southern district but increased markedly in the northern district. Spatial heterogeneity was caused by the spatial distribution of nutrients and the buoyancy regulation capacity of cyanobacteria. The results demonstrate that bloom mitigation responds strongly to nitrogen and phosphorus control in meso-eutrophic lakes, therefore preventing and controlling blooms through nitrogen and phosphorus reduction is still an effective measure. Given the accumulation of organic matter in recent years, synergistic control of organic matter and total nitrogen and phosphorus could effectively reduce the risk of cyanobacterial and dinoflagellate blooms.

The impacts of spatio-temporal variation of natural and agricultural influences on the environmental water quality in a fluvial-lacustrine watershed in China.

Despite the significant impacts of natural factors such as rainfall, topography, soil type, and river network as well as agricultural activities on the environmental water quality, little is known about the influence of their temporal and spatial variations in a fluvial-lacustrine watershed. In this study, a whole process accounting method based the export coefficient model (WP-ECM) was first developed to quantify how natural factors and agricultural activities distribution influenced water quality. A case study was performed in a typical fluvial-lacustrine area - Dongting basin, China. The simulated results indicated that the natural factors can promote and inhibit the migration and transformation of agricultural pollutants generated from the watershed and the spatial distribution of the natural factors displayed high variability. It should be priority to monitor the areas with greater natural impact in the basin. Moreover, the cultivated land area and the number of pig-breeding were positively correlated with the pollutant discharge. From the perspective of the spatial distribution of comprehensive influence, the comprehensive high-impact areas are mainly distributed in the Dongting Lake district in 2005-2010 and in Xiang River watershed in 2010-2020. A key strategy for controlling or reducing the cultivated land area and the intensity of livestock breeding in these high-impacts areas is recommended to reduce the impact of the environmental water quality for the entire basin.

[Distribution Characteristics and Risk Assessment of 209 Polychlorinated Biphenyls in Dongting Lake and the Inflow Rivers].

In order to fully understand the pollution of polychlorinated biphenyls (PCBs) in Dongting Lake, 209 PCB congeners were quantitatively detected and analyzed by isotope-dilution high-resolution mass spectrometry in 21 surface water sampling sites of Dongting Lake and the inflow rivers of the lake. The results showed that a total of 50 PCB congeners were detected in the study area. The ρ(ΣPCBs) ranged from 0.077 to 10 ng·L-1, with an average concentration of 2.7 ng·L-1 and a median concentration of 1.9 ng·L-1. The order of contamination concentrations were as follows:the inflow rivers of the lake > lake region > outlet. Compared with the reports of domestic and foreign studies, PCB pollution in Dongting Lake is at a low level. The main pollutants in the surface water were dichlorobiphenyls and tri- and tetrachlorobiphenyls, with relative abundances of 67%, 14%, and 16%, respectively. PCB11, PCB17, PCB18, PCB20+33, PCB28, PCB47+75, PCB52, and PCB68 were the most widely distributed and detected in more than 80% of samples. Among them, ρ(PCB11) was the highest, with an average concentration of 1.6 ng·L-1, accounting for 59% of ρ(ΣPCBs), from the domestic organic pigment production process of unintentional emissions. Atmospheric transport deposition and historical residue were the main sources of PCBs in water. According to the toxicity equivalent factor method, the ecological toxicity risk of the study area was evaluated, and the results showed that the TEQ in the water was far lower than the relevant standard limit, indicating that the pollution of PCBs in the surface water of Dongting Lake and the inflow rivers would not cause harm to exposed organisms.

[Community of Benthic Diatoms and Their Relationship with Aquatic Environmental Factors in the Tangwang River, China].

To reasonably evaluate the eco-environmental health of the Tangwang River, which is a tributary of the Songhua River in China, community structures of periphyton and cleanliness of the benthic diatom at 24 sampling sites were investigated using McNaughton's dominance index, clustering, and ecotype analysis, while the relationship between the environmental factors and the diatom communities were studied by principal component analysis, Spearman correlation test, and redundancy analysis, in August 2018 (flood season). A total of 99 species or variants of benthic diatoms have been identified, indicating that there were abundant diatoms in the Tangwang River. Achnanthidium minutissimum and other diatoms that can be used as clean water indicators were dominant species in the Tangwang River, which indicates that the eco-environmental quality of the Tangwang River was relatively healthy in the flood season. Of these, the dominant degree of A. minutissimum was 0.32, making it the absolute dominant species in Tangwang River. Sampling sites can be divided into three groups based on clustering analysis. The dominant species of group 1 and group 2 were mainly clean species, indicating that the two groups were in a relatively healthy state. Nitzschia palea, Ulnaria ulna, and other diatoms that can be used as eutrophication indicators were the dominant species of group 3, indicating that group 3 was less healthy than the other two groups. From groups 1 and 2, the results from ecotype analysis showed a decrease in the proportion of polyoxybiontic diatoms and an increase in the proportion of α-mesosaphrobe diatoms, polysaprobe diatoms, oligo-mesotrophic diatoms, mesotrophic diatoms, meso-eutrophic diatoms, and eutrophic diatoms. Compared to the other two groups, the results from ecotype analysis showed a significant increase in the proportion of α-mesosaphrobe diatoms, polysaprobe diatoms, eutrophic diatoms and hypereutrophic diatoms in group 3. The predominant aquatic influencing factors of diatom community structures for the Tangwang River were permanganate index, total nitrogen (TN), and ammonia nitrogen (NH4+-N), of which permanganate index was the main factor for group 2, while TN and NH4+-N were the main factors for group 3. As a result, the eco-environmental quality of the Tangwang River was good, and the benthic diatom was found to be an effective indicator of the nutritional conditions and saprophytic status.

[Analysis of Transport and Transformation Characteristics Between Dissolved Phosphorus and Particulate Phosphorus in Water of the Three Gorges Reservoir].

To understand the difference between transport coefficients of water runoff, sand discharge, and phosphorus flux in each subsection of a river, a judgement method for analyzing the characteristics of phosphorus transport and transformation in water of rivers was established in this study. Based on the measured data of water runoff, sand discharge, and phosphorus fraction concentrations in the water of the Three Gorges Reservoir (TGR) in January and July 2015, characteristics of phosphorus transport and transformation in the water were analyzed by using the conceptual method. The results showed that the predominant phosphorus fraction in water of the TGR was total dissolved phosphorus (TDP), which accounted for 51%-96% of total phosphorus in water. The TDP flux relative to runoff in the TGR decreased in January 2015 That was caused by the adsorption of TDP by suspended particles in the dry season. In contrast, TDP flux showed additive effect relative to water runoff in July 2015 due to exogenous water inputs with high TDP concentrations in the wet season. Both sand and total particulate phosphorus (TPP) presence in the water showed obvious sediment and retention characteristics during the two periods. The TPP flux presented an additive effect relative to sand discharge, meaning that the major transformation direction of phosphorus fractions was from TDP to TPP. The subsection between Qingxichang and Wanzhou was the main retention area of water, sand, and phosphorus in the TGR, which can be associated with the enhancement of phosphorus adsorption capacity caused by particle size reduction of suspended particles in the subsection.

A proposed delineation method for lake buffer zones in watersheds dominated by non-point source pollution.

Although buffer zones around aquatic areas are a useful method for controlling non-point source pollution and restoring natural ecosystem services, proper delineation methods for lakes remain poorly defined, restricting their protection and the rational utilization of resources. As the width of lake buffer zones should be set to meet the area's functional targets and requirements, this study proposes a methodology for delineating these zones that includes critical source areas for non-point source pollution and ecologically sensitive areas. The proposed method was tested on Zhushan Bay, Lake Tai, China given its poor environmental condition and a renewed focus on mitigation by the local government. Data sources and relative processing methods include vector data on land use and hydrographic networks processed by ArcGIS, digital elevation model (DEM) data with 30 m resolution, soil and socioeconomic data from local governmental statistical yearbooks, NPS pollution load into lake obtained by literatures and field survey. The results showed that a minimum buffer range could be practically determined while meeting the requirements of both environmental protection and economic needs, providing a theoretical and practical basis for the improved delineation and management of lake buffer zones in watersheds dominated by non-point source pollution.

Wetland ecosystem status and restoration using the Ecopath with Ecosim (EWE) model.

With increasing awareness of the importance of wetlands, the number of new or restored wetlands in China is steadily growing; however, not all of them fulfill their expected ecological function. Maintaining wetlands in their optimal state is an urgent problem that requires research into the ecosystem evaluation, regulation, and biomass management of wetlands. The Ecopath with Ecosim (EWE) model, also known as the ecological channel model, is a balance model that can directly construct the ecological system structure and describe its energy flow and mass transfer through the principle of nutrition dynamics. Here, the EWE model is applied to determine the ecosystem status of a newly restored wetland, Zhushanhu wetland, in the Lake Tai buffer zone of Zhushan Bay, and evaluate the current ecological regulations and biomass control measures. Our results provide theoretical and scientific support for the management and maintenance of wetland ecological restorations.

[Succession Pattern of Phytoplankton of Daning River in the Three Gorges Reservoir and Its Driving Factors].

To elucidate succession pattern of phytoplankton in the Daning River and its driving factors, multivariate statistical analysis was conducted. By using the monitoring data in different seasons of Daning river during April 2012 to January 2013, this paper analyzed the succession pattern of phytoplankton in the Daning River and its driving factors in typical tributaries of river-style reservoirs. According to the characteristics of water level, the operational period of the TGR was classified into following four stages:stage Ⅰ (pre-November-April), stage Ⅱ (May-July), stage Ⅲ (July-September) and stage Ⅳ (September-November). ① The results indicated that the values of Chlorophyll-a concentrations and algal density showed similar seasonal variations, with the highest values occurring in stage Ⅲ, followed by stages Ⅳ, Ⅱ and Ⅰ. Succession of C-R-S growth strategies was the same generally:CR-R type dominated in stage Ⅰ, CS, CR/CS and R-CR dominated in stage Ⅱ, Ⅲ and Ⅳ, respectively. ② The mean values of Margalef index and Pielou index in stage Ⅳ and Ⅲ were significantly greater than those in stage Ⅱ and Ⅰ; the value of Shannon-waver index showed that the highest value in stage Ⅲ, followed in a descending order by stage Ⅰ,Ⅱ and Ⅳ; the successional rate had the highest value in stage Ⅳ, followed in descending order by stage Ⅲ, Ⅰ and Ⅱ. ③ The results of Correlation analysis suggested that no significant relationships were observed between the environmental parameters and phytoplankton abundance in stage Ⅰ. The results indicated that relative water column stability(RWCS), index of feasible energy for phytoplankton (Et) and index of feasible energy (Ef*) were key regulatory factors for phytoplankton community in stage Ⅰ. The results indicated that Et, Ef* and total phosphorus (TP) were key regulatory factors for phytoplankton abundance in stage Ⅱ. The results of the redundancy analysis (RDA) suggested that RWCS, TP and the ratio of euphotic depth[Deu(λPAR)] to mixing depth (Dmix)[Deu(λPAR)/Dmix] were key regulatory factors for phytoplankton community composition in stage Ⅱ. The results indicated that Ef* and TP were key regulatory factors for phytoplankton abundance in stage Ⅲ. The results of the RDA suggested that[Deu(λPAR)/Dmix],Et, Ef* and TP were key regulatory factors for phytoplankton community composition in stage Ⅲ. The results indicated that TP was key regulatory factor for phytoplankton abundance in stage Ⅳ. The results of the RDA suggested that[Deu(λPAR)/Dmix] was key regulatory factor for phytoplankton community composition in stage Ⅳ.

[Response Behaviors of Heavy Metals at Tidal Currents Interface and Salinity Interface in the Estuary Area].

In China, trace metals (such as dissolved Cu, Zn, Pb, Cd, and Cr) are the routine mandatory monitoring indicators in existing Freshwater Quality Standard (FWQS, 2002) and Seawater Quality Standard (SWQS, 1997). Using Daliao River estuary as an example, we tried to research the general response patterns of these metals in estuarine system. Firstly, we determined the location of FSI (freshwater-seawater interface) and TCI (tidal currents interface), which were based on biological, chemical and geographic similarities by descriptive and quantitative methods, respectively. Secondly, two hypotheses were proposed to explain the difference based on distribution coefficient Kd along salinity and SS (suspended solids) gradient, these results revealed that the indicators for As, Cd and Cr may be prone to be affected by salinity, and the ones in the second pattern may be more sensitive to SS. Finally, we classified the response behaviors into two patterns based on the changing trends along the distance and magnitudes affected by the FSI and TCI: 1the obvious boundary break point from FSI for As, Cd and Cr; 2 the boundary zones from TCI for Zn, Cu, Pb and Ni. The partitioning behaviors showed similar changing trends at particle and sediment phases, especially for particle phase, depending on the concentration of SS along the salinity. The difference between general behaviors for the two patterns mainly existed at water phase. In general, this paper highlighted the need to consider the background difference of trace metals and identified the sensitive indicators controlled by different environment factors (such as salinity and SS) based on the native estuarine characteristics. Our work will assist the implementation of updating the current water quality standards in China.

Transcriptomic response to estrogen exposure in the male Zhikong scallop, Chlamys farreri.

The transcriptomes of Zhikong scallop exposed to 17ß-estradiol were determined using the Roche/454. A total of 51,997 unigenes, representing 45,030 contigs and 6967 singlets were obtained. And 14,028, 19,798 and 14,981 of these unigenes were annotated from the non-redundant nucleic acid database, non-redundant protein database and Swiss protein database, respectively. A total of 10,699 unigenes were further annotated to biological processes (9080), molecular functions (8692) and cellular components (7829) using the GO, and 8945 unigenes were mapped to biological pathways including the metabolism (2862) and genetic information processing (2263). Most importantly, 16,692 unigenes and 18,686 unigenes in testis, and 10,492 unigenes and 13,186 unigenes in digestive gland were up-regulated significantly after exposure to 50 and 500 ng E2/L; while 10,212 unigenes and 9409 unigenes in testis and 10,629 unigenes and 9463 unigenes in digestive gland were down-regulated. These valuable information provides insights into the mechanisms in invertebrate exposure to EDCs.

[Optical signatures of chromophoric dissolved organic matter in water body of Tien Lake].

The water samples of the Tien Lake were collected for the three-dimensional fluorescence spectrum detected. And parallel factor analysis (PARAFAC) and principal component analysis (PCA) were used for the spectra analyzing to know the main factor and relative contribution of the chromophoric dissolved organic matter (CDOM). PARAFAC decomposed CDOM into four components, the humic-like: C1 (240, 415), C3 (265, 525), C4 (255, 505) and the protein-like: C2(230/280, 330). The fluorescence intensity of CDOM components was high in north and estuary of the lake, but low in the other region. All the four components show significant positive correlations (p < 0.01), this result means they may have the same sources. Principal component analysis shows that these four components of the Tien Lake are all from terrestrial organic matter, meanwhile its DTN, DTP, DON may also come with the terrestrial substance. These components of Tien Lake can well be connected with dissolved nutrient salts by nonlinear multiple regression, which means we can use the three-dimensional fluorescence spectrum results of CDOM to indicate the eutrophication degree of Tien Lake.

[Temporal-spatial distribution and pollution assessment of heavy metals in the upper reaches of Hunhe River (Qingyuan section), northeast China].

The aim of this article is to explore the pollution level and contamination degree of heavy metals in the upper reaches of Hunhe River (Qingyuan Section). The contents and temporal-spatial distribution of Fe, Mn, Cu, Zn, Cd and As in surface water and surface sediments from the upper reaches of Hunhe River were analyzed respectively. The integrated pollution index and geoaccumulation index were used to evaluate the contamination degree of Cu, Zn, Cd and As. The results indicated that the contents of Mn, Cu, Zn, Cd and As in surface water from the upper reaches of Hunhe River during the wet season were higher than those during normal and dry season. Similar patterns of spatial distribution of Fe, Mn, Cu, Zn and Cd in surface water were observed, which showed that the highest content appeared at H7 station. The influence of pH, DO and hardness in the upper reaches of Hunhe River during the wet, normal and dry season on the distribution of heavy metal contents in surface water varied. Significant positive correlations were found among these elements in surface water, which implied that these elements probably had common pollution sources. The contents of Cu, Zn, Cd and Fe in surface sediments from the upper reaches of Hunhe River during the dry season were higher than those during the wet and normal season. Similar patterns of spatial distribution of Mn, Cu, Zn, As and Cd in surface sediments were also observed, which showed that the highest metal contents appeared in the midway of Hunhe River. The integrated pollution index assessment showed that the water quality in the upper reaches of Hunhe River was good except for individual stations, and that Cu, Cd and As were the main pollution elements in surface sediments in the upper reaches of Hunhe River.

Evidence for the presence of sex steroid hormones in Zhikong scallop, Chlamys farreri.

To obtain evidence of the presence of sex steroid hormones in mollusks, hormone variation in the gonads of the Zhikong scallop Chlamys farreri was analyzed using UPLC-MS/MS. These were found, as expected, with concentrations of estrone (E1), 17beta-estradiol (E2), and testosterone (T) in the testes ranging from not detected (ND) to 0.07 ± 0.10, ND to 3.10 ± 2.00, and ND to 2.67 ± 1.55 ng/g wet weight, respectively. In the ovaries, these hormones ranged from ND to 2.45 ± 1.22, ND to 27.90 ± 4.23, and ND to 2.38 ± 1.56 ng/g ww, respectively. The levels of T in males and E2 in females followed a trend similar to the gonadal-somatic index over the course of the reproductive period. In addition, the gene expression of vitellogenin and calmodulin-2 showed similar patterns to T and E2, while the estrogen receptors and calmodulin-1 did not. These results indicate that sex steroids are present in the scallop and that they may regulate endocrine functions during the reproductive process.

Use of heat shock protein mRNA expressions as biomarkers in wild crucian carp for monitoring water quality.

In organisms, the production of heat shock proteins (HSPs) can be induced after exposure to various stressors. In the present study, partial cDNA sequences encoding of HSP30, HSP60, HSP70, and HSP90 genes were isolated and sequenced in the crucian carp (Carassius carassius). Next, quantitative real-time reverse transcription PCR (qRT-PCR) assays normalized to beta-actin were developed to quantify HSP mRNA expression. The same methods were used to detect HSP mRNA expression in the wild crucian carp that were collected from the Hun River. In fish located downstream of the river, we found that the levels of HSP70 and HSP30 in the liver and kidney were higher than fish located upstream, and these differences coincided with changes of the water quality. These results suggest that kidney HSP30 and liver HSP70 expression can serve as sensitive biomarkers for the presence of field environmental stressors in wild crucian carp.

[Distribution characteristics and risk evaluation of organochlorine pesticides in soil from relocation areas of the Danjiangkou Reservoir].

Twenty-six surface soil samples collected in Danjiangkou Reservoir were analyzed for organochlorine pesticides (OCPs) residues by GC-MS. The distribution characteristics, compositions and origin of OCPs were discussed. Pollution level and potential ecological risks of OCPs were also evaluated. The results showed that the concentration rang of total OCPs in soil was nd-249.37 ng x g(-1) (with a mean of 24.82 ng x g(-1)). The recent occurrence levels in soil were nd-69.68 ng x g(-1) for HCHs and nd-104.53 ng x g for DDTs. DDTs concentrations in soil were higher than those of HCHs. The OCPs residues in soil were mainly originated from the early residues, atmospheric deposition and recent input of OCPs components. The correlation between OCPs contents and organic matter contents in soil was not significant, indicating that the contents of OCPs in soil were also affected by other factors. Compared with other soil samples from different regions, the contents of OCPs in soil of relocation areas of the Danjiangkou Reservoir were at medium-low level. The study suggested that the OCPs in soil of relocation areas of the Danjiangkou Reservoir are in a state of low danger, whereas OCPs still display risks locally in some places.

[Application of equilibrium partitioning approach to establish sediment quality criteria for heavy metals in Hengyang section of Xiangjiang River].

Twenty-nine surface sediment samples were collected from Hengyang sections of Xiangjiang River to detect concentrations and speciation percentage of heavy metals (Cu, Pb, Zn and Cd) in sediment and pore water. According to the Equilibrium Partitioning (EqP) approach, the sediment-water partition coefficients (Kp) of heavy metals in Hengyang section of Xiang River were revised by the bioavailable fraction, and the USEPA Criterion Continuous Concentration(CCC) which was based on aquatic toxicity of the final chronic level and GB3838-2002 I ,water quality standard were introduced to establish two types of sediment quality criteria (SQC) for heavy metals (Cu, Pb, Zn and Cd) in Hengyang section of Xiangjiang River for comparison. The better SQCs (base on CCC) of Cu, Pb, Zn and Cd were 64.62, 55.57, 1 360.40 and 2.34 microg x g(-1), and they can protect benthic organism from being poisoned by heavy metal chronic aquatic toxicity. The ratio of heavy metal concentration and SQC was used to assess sediment quality in Hengyang section of Xiangjiang River, the result showed that concentration levels of Cd, Pb in sediment in Hengyang section of Xiangjiang River had strong chronic toxic effects, Cd pollution could not be ignored.

[Temporal-spatial distribution of algal cells during drought period in Daning River of Three Gorges].

In order to provide basic data for algal bloom warning system, the study on temporal-spatial distribution of algal cells was carried out in Daning River of Three Gorges form April to September, 2011. The results of temporal distribution were as follows: the dominant algal species were blue algal, green algal and diatom. During the test, the density proportion of blue algae increased continuously, the density proportion of diatom decreased, while the density proportion of green algae did not change significantly. The results of spatial distribution were as follows: algal density was extremely significantly correlated with water temperature and chlorophyll a (Chl a), the correlation coefficient were 0.97 and 0.95, respectively; algal density was significantly correlated with light intensity (LI), dissolved oxygen (DO), pH and dissoluble total phosphorus (DTP), the correlation coefficient were 0.87, 0.83, 082 and 0.82, respectively; the algal density in 0 m of Caziba was higher than those in other water depths, and in Baishuihe the highest algal density occurred at 2.0 m water depth in June and July, in Shuanglong most algal cells were found in 0 m and 2.0 m in July, August and September, in Dachang algal density in different water depth did not change significantly during the test; the proportion of different algal species in vertical direction was different in the test, probably because different algal species fitted different environments.

[Study on the ecological risk of wild veined rapa whelk (Rapana venosa) exposured to organotin compounds in Bohai Bay, China].

The present study evaluated the potential ecological risk of organotin compounds (OTs) to wild veined rapa whelk (Rapana Venosa) population in Bohai Bay. The results showed that the imposex rate was 12.5% and 6.48% in Dashentang and Nanpaihe coastal areas, with relative penis size index of 9.61 and 12.45, respectively. The concentrations of butyltin compounds and phenyltin compounds were 39.04 ng x g(-1) dw and 46.48 ng x g(-1) dw in muscle tissues, and 32.09 ng x g(-1) dw and 109.03 ng x g(-1) dw in digest gland, respectively. Based on TBT levels in the muscles of all samples, a risk quotient of 0.024 was derived, indicating certain risk of OTs at current levels to wild veined rapa whelk populations in Bohai Bay.