A Preliminary Study Of Algal Inhibition Mechannism On Phaeocystis Globosa Under Combined Nitrogen-containing Compounds

Phaeocystis globosa is a notorious HAB species,frequently broke out in China,which caused nuisance foam and oxygen depletion and released toxic hemolytic substances,which has seriously destroyed marine ecosystem,caused enormous economic losses and threats to human health.Bacillus sp.strain B1 was previously isolated from the bloom of Phaeocystis globosa in Zhuhai,China,and the algicidal substances were identified as L-histidine,N-acetylhistamine,and urocanic acid.Based on it,we conducted the verification experiment of single and combined algicidal effect and obtained specific combined actions of their binary mixtures.Besides,effect of antioxidant system,morphological change,cell structures and hemolytic toxin,changable compisition of algal toxin were also clarified.The major research results are as follows:?1?The 96h EC₅₀0 values in the single algicidal validation test indicated a algicidal effect order of urocanic acid?8?g/m L?>N-acetylhistamine?16?g/m L?>L-histidine?23?g/mL?.The results of algicidal test on binary mixtures indicated that additional index?AI?showed synergistic effect for binary mixture uro+ace,antagonism fo binary mixtures uro+his and ace+his.?2?Through detected Phaeocystis globosa antioxidant system found that binary mixture uro+ace could increase the MDA content,SOD and CAT activity significantly.?3?FESEM and TEM analysis revealed morphological change and alterations of the ultrastructure of Phaeocystis globosa.The results showed that the main targeted site may be different,uro?mainly disrupting the chloroplast and nucleolus?and ace?deteriorating membrane permeability?enhanced algicidal action,which further verified that there was synergism exists between uro and ace.?4?In experiment of hemolytic activity,results showed that after exposure to the nitrogen-containing compounds at a concentration of EC₅₀?single action?and 1:1EC₅₀?combined action?for the fifth day,the activity in single uro,ace and binary mixture uro+ace treatment had declined by 37.6%,52.5%and 67.5%respectively to the control,which showed that binary mixture uro+ace had stronger effect on hemolytic activity.?5?HPLC and GC-MS was used to detect nitrogen-compounds effect on Phaeocystis globosa toxin solution and fatty acids.The HPLC results showed that both in control group and experimental group have 8 components.However,uro+ace binary mixtures can inhibit the synthesis of both the forth and first component.The GC-MS results showed uro+ace binary mixtures can inhibit the synthesis of the major fatty acids C₁₇H₃₂O₂ and C₁₉H₃₄O₂,which revealed that the ability of synthesising fatty acids and the toxicity were decreased significantly.