| In recent years, with the rapid development of urbanization, the discharge of industrial wastewater and urban sewage lead to serious eutrophication of lakes and other bodies of water. Eutrophication of waters causes algae’s explosive growth beyond the water purification ability, which appeared in the "bloom" phenomenon. Cyanobacterial blooms are particularly common. The occurence of Cyanobacterial blooms not only break the normal water ecological structure, but also bring some threats to fish, shrimp, shellfish in water and the safety of human life. Because of the frequent outbreaks of Cyanobacterial blooms, more and more attentions are paid to its management. It becomes extremely important for us to find effective ways to control the growth of algae in eutrophic water and prevent the occurrence of water blooms.The common algae removal technology contains physical methods, chemical methods and biological methods. But these methods have certain disadvantages. Using the allelochemicals secreted by aquatic plants to inhibite growth of algae becomes very common in recent years. It is said that this method is effcient, rapid and ecological security. Therefore, It’s considered one of the most promising algae inhibition way.Four typical aquatic plants, Phragmites australis, Polygonum orientale, Myriophyllum spicatum, Typha orientalis. and a kind of bloom algae Microcystis flosaquae were studied in this research. Cell density, chlorophyll α, β-carotene, phycobilin content, changes of SOD activity and cells morghology of Microcystis flosaquae were tracking measured and observed. The inhibition of four aquatic plants’water extracts with different concentrations (0g/L,5g/L,10g/L,20g/L,30g/L,40g/L)on Microcystis flosaquae were studied. The results were as follows:(1)Effects of different concentrations of four aquatic plants water extracts on the cells density of Microcystis flosaquae:Phragmites australis water extracts with low concentrations (5g/L 10g/L,20g/L) showed significant promotion effect on cell density of Microcystis flosaquae, while extracts with high concentrations (30g/L,40g/L) showed inhibitory effect. Polygonum orientale water extracts with low concentrations (5g/L,10g/L,20g/L) suggested promotion effect on cell density, in contrast, extracts with high concentrations (40g/L) suggested inhibitory effect. Cell density of treatment group (30g/L) changed like the control group. Different concentrations of Typha orientalis extracts showed promotion effect on cell density of Microcystis flosaquae mostly. Whereas, Different concentrations of Myriophyllum spicatum showed certain inhibitoty effect on cell density.(2)Effects of different concentrations of four aquatic plants water extracts on the pigment content of Microcystis flosaquae:Phragmites australis water extracts with low concentrations (5g/L,10g/L,20g/L) showed significant promotion effect on chlorophyll a and β-carotene content of Microcystis flosaquae, while extracts with high concentrations (30g/L,40g/L) showed inhibitory effect. But for phycobilin content, different concentrations of Phragmites australis extracts showed promoting effects. In the low concentration (5g/L,10g/L,20g/L) treatment groups of Polygonum orientale, chlorophyll a, β-carotene increased significantly with time went by, so they presented promoting effect. While, for the treatment group of30g/L, it presented like the control group. And for the group of40g/L, it showed the inhibiting effect. Different concentrations of Typha orientalis extracts showed promotion effect on chlorophyll a, β-carotene of Microcystis flosaquae. In contrast, Different concentrations of Myriophyllum spicatum showed certain inhibitoty effect on chlorophyll a, β-carotene and phycobilin content.(3)Effects of different concentrations of four aquatic plants water extracts on the SOD activities of Microcystis flosaquae:Compared with the control group, for the treatment group5g/L,10g/L,20g/L of water extracts of Phragmites australis, their SOD activities enhanced significantly, While for the group of30g/L,40g/L, their SOD activities decreased obviously. Under different concentration of extracts of Polygonum orientale, there was only SOD activity of40g/L group increased. For different concentrations of water extracs Typha orientalis, SOD activities enhanced significantly in three days. But it decreased to the initial level in fourth day. For different concentration of water extracts of Myriophyllum spicatum, there were rising trend of SOD activities and effect of concentration, that was with concentration increased, its SOD activity enhanced.(4)Effects of Phragmites australis water extracts on the cell structure of Microcystis flosaquae:Cell distribution of Microcystis flosaquae was homogeneous before added water extracts, there was not a phenomenon of aggregation, and also the photosynthetic pigment was not destroyed. When added30g/L40g/L concentration of water extracts of Phragmites australis to culture medium of Microcystis flosaquae, algae cells immediately gathered and sunk to the bottom. The second day, most algae cells of photosynthetic pigments damaged severely, even more, some cells broke up. The fourth day, almost algae cells of photosynthetic pigment and structure damaged.In conclusion, The inhibition of four kinds of extracting solution of aquatic plant to Microcystis flosaquae:Phragmites australis Myriophyllum spicatum>Polygonum orientale>Typha orientalis... |
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