Investigation On The Inhibition Mechanism Of Ceratophyllum Demersum And Spirogyra On Microcystis Aeruginosa

Nutrient availability is the main reason for the outbreak of algal blooms. Microcystis aeruginosa is the main algae which results in eutrophied waters in Chinese lakes, reservoirs and other aquatic ecosystem.Aquatic plants and algae, as the energy and material flow basis of the water eco-system, have strong overlapping in the ecological niche and fierce competition for nutrition, light, space between each other. Hydrophtes play a key role in improving water quality, cleanning water, increasing water dissolved oxygen, providing a output channel of nitrogen and phosphorus, and regulating aquatic ecosystem biological structure.Therefore, it is important to restore aquatic macrophytes, especially the macrophytes of releasing allelopathic substances for growth inhibition of the algae in the eutrophic aquatic ecosystem. However, the practical application of aquatic plants faced low efficiency, poor ecological safety and fragile environment endurance. So, selecting the aquatic plants of high efficiency, ecological security, strong environment endurance, is the focus of resroration of eutrophied waters. Ceratophyllum demersum and Spirogyra are two common aquatic macrophytes in most water bodies of China Ceratophyllum demersum have been well known for its high ability of growth inhibition of algae through production of allelopathic substances and competing for nutrition, light, space. But, there are few studies about allelopathic inhabition activity of Spirogyra on algae.In this thesis, the allelopathic inhibition activity on Microcystis aeruginosa is investigated from two parts. In the first part, the molecular mechanism about growth inhibition of Ceratophyllum demersum on Microcystis aeruginosa were studied. The results showed Ceratophyllum demersum can inhibit the growth of Microcystis aeruginosa and affect its physiological function after Co-culture of 1g Ceratophyllum demersum and Microcystis aeruginosa.Ceratophyllum demersum can lead to the loss of Phycobiliproteins in Microcysti s aeruginosa cells. The loss of Phycocyanin(PC) was the most, and got 19.5%; Allophyxoxya nin (APC) and Phycoerythrocyanin (PE) was relatively less, and was 71.7% and 77.6%, respe ctively. Using the PCR microarray and realtime PCR assay, we found that the gene expression of of Microcystis aeruginosa cells was altered after co-culture of Ceratophyllum demersum and Microcystis aeruginosa. The gene expression of Microcystis aeruginosa was altered after treated with Ceratophyllum demersum. Compared with the control group, in the treatment group of Microcystis aeruginosa, the genes (cpcA1 cpcB1 cpcC1, cpcC2) related P hycocyanin, the genes (mcyA、mcyB、mcyC) related microcystin synthetase, the FtsZ gene related cell division, the original chlorophyll oxidoreductase gene(pro) and atpase gene (Atp, atpCa) were low expression. The genes (KaiA, KaiB, KaiC) related to li fe rhythm, FAD dependent oxidoreductase gene (fdo) were high expression. The results showed that the gene expression of of Microcystis aeruginosa were influenced by Ceratophyllum demersum. As a result, these data implied that Ceratophyllum demersum can influence the physiological function of Microcystic aeruginosa probably through altering the gene expression of Microcystis aeruginosa.In the second part, the Spirogyra was found as a aquatic macrophyte which releasing allelopathic substances for growth inhibition of the algae. Compared with Ceratophyllum demersum, the inhibition effects on Microcystis aeruginosa of Spirogyra is same as Ceratophyllum demersum. The culture solution of Spirogyra can strongly inhibit the growth of Microcystis aeruginosa, which stimulated destruction of its chlorophyll-a and increased of its MDA contents. The inhibition activity was more effective with the concentration rising of the culture solution. To solve the problem of the Spirogyra’s low tolerance to eutrophic water,The Spirogyra co-cultivating with Ceratophyllum demersum experiments were performed. The results showed the coexistence system promoted the growth and biomass of the two macrophytes, and enhanced the tolerance of the Spirogyra in eutrophic water. The inhibition effects on Microcystis aeruginosa of culture solution from the coexistence culture system were more significant than the culture solution of the individual algal tests. When the ration of Spirogyra to Ceratophyllum demersum was 6:4, the inhibition effects reached a maximum, as well as the biomass increasing. These results suggested that the inhibition effective of Spirogyra and Ceratophyllum demersum on the growth of Microcystis aeruginosa can be promoted by each other.These data provides the basic research and guidance for the future application of Ceratophyllum demersum and Spirogyra in eutrophic aquatic ecosystem restroration.