Inhibitory effect of three allelochemicals on growth of Microcystis aeruginosa

The inhibitory effects of extracts from 60 plant samples on Microcystis aeruginosa were investigated by measuring the cell number of Microcystis aeruginosa during the cultivation process.8 plant extracts presented remarkable anti-algae activity,their inhibitory ratio to Microcystis aeruginosa were all above 90%.The inhibitory effects of three most effective samples,Magnolia grandiflora,Sophora japonica f.pendula and Buxus sinica,were further measured,their inhibition ratio to Microcystis aeruginosa were calculated as 97.4%,95.6% and 91.2%,the medial effective concentrations (EC50) for seven days were 0.52,1.04 and 5.87 g/L,and EC90 were 3.79,6.45 and 9.09 g/L,respectively.The fitting equations between EC50 and culture time showed that the inhibitory effects of Magnolia grandiflora and Sophora japonica f.pendula to Microcystis aeruginosa would not decrease with the elongation of incubation time.The above results revealed that the three land-floras contained very high levels of anti-algae allelochemicals,they might have a great potential to treat algae bloom and control the eutrophication of water.