Inhibitive effects of organic solvent extracts from mangrove plant Bruguiera gymnorrhiza on Phaeocystis globosa

Based on allelopathic principles,we used organic solvents to extract the active substances from mangrove plant Bruguiera gymnorrhiza,and extracts of hexane phase,ethyl acetate phase,n-butyl alcohol phase and water phase were obtained respectively.The experiment was carried out to test the inhibitive effects of these extracts on algae.Measuring the cell density of Phaeocystis globosa,we found that all of the extracts had significantly inhibitive effects on P.globosa,and the inhibitive effects of extracts of hexane phase and ethyl acetate phase were better than those of n-butyl alcohol phase and water phase.The 48h-EC50 of extracts of hexane phase and ethyl acetate phase on P.globosa were 14.90 mg/L and 12.18 mg/L,respectively.The initial algal density(IAD) was considered an important factor to influence the inhibitive effects of extracts.The inhibitive rate(IR) was high at low IAD,while it decreased with the increasing of IAD.At a higher IAD,the extracts promoted the growth of P.globosa,rather than inhibited the growth.