Inhibitory Effect Of Chinese Herb On Microcystic Aeruginosa And Its Mechanism

Microcystis blooms could deteriorate aquatic environments, cause harm to aquatic animals, and destroy the equilibrium of the aqua-ecosystem. To provide the basic knowledge for developing environment-friendly algicides with high efficiency,the inhibitory effects of Chinese herb on Microcystic aeruginosa and its mechanism involved are studied in present paper.Based on the antialgal results of sampled Chinese herb, golden thread （Coptidis rhizome, Huang lian in Chinese） showing best algal inhibition was screened. Further studies are conducted to reveal the effects of several alkaloids in golden thread on M. aeruginosa in laboratory and field, as well as on the micro-ecosystem. Meanwhile, the effects of several main environment factors on the algal inhibition are studied. Moreover, the antialgal mechanisms of the alkaloids have been studied from the view of photosynthesis, oxidation defense system, and the ultrastructure of M. aeruginosa. The main results of the present study are presented as follow:1. Golden thread, exhibited the best inhibitory effects, can act as effective algicide. Effective concentration of golden thread for suppressing M. aeruginosa is 0.100%（W/V）. 96 h inhibitory rate （IR） is 95.15%, and the linear equation is Y= 1.6510-4.5192×C-0.008×T （Y: algal density, C: concentration of golden thread, T: exposure time）.2. The results show that alkaloids might be the allelopathic substance of golden thread implementing inhibitory effects on M. aeruginosa. The berberine, either extracted from the golden thread or synthesized by industry, exhibits strong inhibitory effects on M. aeruginosa in laboratory and field, 96 h IR of 0.020% berberine is more than 90.00%. Although the main physical and chemical index of micro-ecological water has been affected in varying degrees by berberine, Carassius aurutus are influenced insignificantly （p > 0.05） under the stress of berberine.3. Ultrastructure destruction, oxidative damage and photosynthetic pigments change might be involved in alkaloids -induced antialgal mechanisms. alkaloids binds with DNA and destroys DNA structure, leading to ultrastructure destruction of algal cell. It is observed that the number of algal thylakoids and phycobilisomes decrease, accompanying with the increases in the number of cyanophycin granules, plastoglobuli and polyhedral bodies. Moreover, the smooth cell membrane and the multiple-layered cell wall are ruptured. The selective permeability of cell membrane has changed, while Ca²⁺Mg²⁺-ATPase activity is inhibited. Photosynthesis is influenced by alkaloids too. Meanwhile, MDA content and O2- activity of M. aeruginosa under alkaloids stress increase with the enhancement of exposure concentration and the prolongation of exposure time. Berberine upregulates SOD activity and GSH content at low concentrations while downregulating SOD activity at high concentrations. In general, alkaloids could destroy DNA and ultrastructure of M. aeruginosa, change the selective permeability of algal cell membrane, inhibit Ca²⁺Mg²⁺-ATPase activity and photosynthesis, induce increase in O2- activity and decrease in SOD activity, destroy the antioxidant defense system, lead to lipid peroxidation and oxidative damage, and inhibit the metabolism processes of M. aeruginosa, eventually result in the death of the algal cell.