| With the rapid economic development of Shanghai and population, the quantity of water resource is getting scarce. As one of the water resource protected area, Dianshan Lake is suffering the growing eutrophication and high frequent algae bloom recent years, which seriously threaten the aquatic ecosystem security; Although the development of Qingcaosha reservoir provides a reliable guarantee to the city’s drinking water, it also exists potential risk of algae bloom. Therefore, how to protect the safety of water resources and prevent eutrophication is the priority for Shanghai government now.The two research objects, Dianshan Lake and Qingcaosha reservoir were studied in this study. Based on regular sampling of water, the water index and microorganism were detected, and the dynamic variation of bacteria and cyanobacteria community structure by molecular biology methods such as PCR-DGGE and Real-time quantitative PCR. The temporal-spatial change law of microbial community and the relationship between environmental factors were analyzed by statistics methods, and then provide theoretical reference to ecological rehabilitation for eutrophication and algae control of the waterhead area.The main results of Dianshan Lake are as follows:(1) During the research period, the nutrion index as TN and TP in Dianshan Lake were inferior to water environmental standard class Ⅳ to Ⅴ, as the eutrophication was more serious; Spatial differences are significant, showing the characteristic that north area of lake (P5,P7)>west area (P9)>the middlel area (P10)> northwest area(P8>south area(P11)>east area(P1,P2). TN was a significant positive correlation with DO and temperature; and positively correlated with NH3-N.(2) The detection range for whole-cell duplex PCR was105～102cell/mL, while to the cyanobacteria, its lower detection limit was100cell/mL, while to the microcystis was102cell/mL. It proved this method was simple and convenient for the express test of cyanobacteria in water. The detection rate of cyanobacteria in Dianshan Lake was46%in spring, and100%in summer, while decreased to23%in winter.(3) The results of cyanobacteria community structure dynamic variation in Dianshan Lake showed that quantity of species in spring and summer were more than that in autumn and winter, showing the feature that summer> spring> winter> autumn; in spatial distribution, it showed that west area>north area>south area> east area. The highest diversity index was in summer (July) and lowest in autumn (October). Since some individual dominant species growing too much inhibited other species in August to September as the algae bloom season, the diversity index fell instead of rising.(4) The DGGE results of cyanobacteria community showed that50%of the dominant species had high homology with Microcystis such as Microcystis aeruginosa, Microcystis flos-aquae, etc., these dominant species existed mostly in the monitoring months and sampling sites, indicating that Microcystis was the dominant species in cyanobacteria community in Dianshan Lake. The cluster analysis results of different sampling sites showed that Dianshan Lake water area could be divided into two parts as southwest and northeast; the two parts of waterare had a higher similarity within their own area, but the similarity between the external was lower. Variation of cyanobacteria community structure was under influence of temperature, showing that in the same season the species had higher similarity, while lower in different quarter.(5) Canonical correspondence analysis (CCA) showed that some dominant species were influence by temperature (T), orthophosphate (MPO4) and total phosphorus (TP), while others were affected by pH and DO; orthophosphate (MPO4) and total phosphorus (TP) affected significantly on cyanobacteria community in summer, while influenced by total nitrogen (TN), dissolved oxygen and pH in autumn and winter.The main results of Qingcaosha reservoir are as follows:(1) During research period, the concentration of TN inside Qingcaosha reservoir ranged from0.12to0.38mg/L, and the concentration of TP ranged from0.011to0.097mg/L; Amplitude of variation between different sampling sites was small but changed acutely with seasons, as the water quality in November was better than other months. The concentrations of TN and TP inside Qingcaosha reservoir were lower than outside the reservoir, which promoted one class of water standard and indicated the reservoir had its self-purification. The ratio of TN/TP in most samples was less than29, so it showed potential risk for growth of cyanobacteria in this reservoir, and phosphorus was a limiting factor to alage.(2) The result of bacteria counting indicated three features:quantity of bacteria changed obviously with the seasonal variation, showing the trend that summer> winter>autumn; The sampling site outside the reservoir R11and sites near this point possessed more biomass than the sites in the middle and tail of the reservoir; there was a significant impact on distribution of microorganisms in the water by sedimentation.(3) DGGE results of microbial community about bacteria abundance and diversity index, showed the trend summer>spring>winter>autumn; In spring and summer, there was no obvious change of microbial species outside and inside, while in autumn and winter, the number of bacteria species in the site outside the reservior was less than other sites inside, diversity index also dropped. And variation of the cyanobacteria community was similar with the bacteria community. Most of dominant species had high similarity with α-Proteobacteria, β-Proteobacteria, Bacteroidetes, Flavobacterium, Rheinheimera, Prochlorococcus, Synechococcus and so on. Cluster analysis showed that seasons change would influence the bacteria community structure; and there was tremendous difference between the site outside the reservoir and inside.(4) The real-time PCR results showed that the bacteria content of the site outside the reservoir was more than other sites inside, and fluctuated small with seasons, while the cyanobacteria concentration was on the contrary, which indicated the content of bacteria decreased while the cyanobacteria increased after the water flew into the reservoir and it fluctuated with seasons showing the trend that declined from summer to winter. And the result of microcystis had the same trend with cyanobacteria on temporal and spatial variation. The relative abundance of cyanobacteria community means in the proportion of the total bacterial content, showed summer was higher than autumn and winter, and the relative abundance of microcystis community means in the proportion of the total cyanobacterial content had no significant dynamic changes with seasons.(5) The correlation analysis between quantitative results and environmental factors as TN and TP, showing that the changes of total bacteria content inside the reservoir had positive correlation with the concentration of TP, while outside the reservoir had no relationship with TN and TP. Cyanobacteria and microcystis had significant positive correlation, and they all had no correlation with TN and TP. |
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