Effects Of Phosphorus And Trace Elements On The Growth And Toxicity Of Microcystis Aeruginosa

Microcystis aeruginosa is a typical dominant species in cyanobacteria bloom.It is generally believed that reducing nitrogen and phosphorus load is the main way to control the excessive growth of M.aeruginosa.However,many engineering practice also found that after controlling the load of nitrogen and phosphorus,the eutrophication of water body is still frequent.Therefore,in recent years,some studies have taken nitrogen and phosphorus sources as the main control means,with trace elements as the auxiliary means to develop the eutrophication phenomenon of water body gradually.In this study,the effects of phosphorus and trace elements on the growth and toxicity of M.aeruginosa were investigated.Based on the nitrate as the nitrogen source;with inorganic phosphorus potassium hydrogen phosphate(K2HPO4),small molecule organic phosphorus glycerin sodium phosphate(Na Gly)and macromolecular organic phosphorus lecithin(LEC)as phosphorus source;Use Fe,Mn,Zn,Cu,Mo as the typical trace elements,through batch culture experiments,the characteristics and mechanism of the growth and toxicity of M.aeruginosa were studied.The main conclusions were as follows:(1).Under high phosphorus conditions(TP=0.5mg·L-1),K2HPO4 was the most conducive phosphorus source to the growth of algae,different trace elements mainly lead to differences in the effect of Na Gly and LEC on the growth of algae,under the environment of Fe and Mn,Na Gly was greater than LEC,while LEC was more effective in Zn,Cu and Mo environment.Under the condition of low phosphorus(TP=0.1mg·L-1),in the environment of Cu and Mo,K2HPO4 was the most significant phosphorus source for algae growth,while in Fe,Mn and Zn environment,Na Gly had better promotion effect on algae growth than other phosphorus sources.(2)Fe,Mn and Zn were three trace elements that significantly affect the growth of algae,which were not only related to the phosphorus load,but also had a significant correlation with the phosphorus source.Especially under low phosphorus conditions,Fe,Mn and Zn can significantly promote the absorption and utilization of algae to small molecule organophosphorus Na Gly.The effects of Cu and Mo on the growth of algae were relatively weak.(3)The average amount of single cell toxicity(MCcell)could be used as a marker for the synthesis of microcystin in different environment.High phosphorus conditions,K2HPO4 was to promote the MCcell synthesis of phosphorus obviously,trace elements in the Fe environment,MCcell had the largest amount;low phosphorus conditions,LEC played a most significant role in promoting MCcell in Cu environment.In other trace elements,Na Gly and K2HPO4 promoted MCcell more than LEC.The production of MCcell was the largest in the Mn environment,This research focused on two representative phosphorus concentrations of TP 0.5mg·L-1(First grade A effluent standard for municipal sewage)and 0.1mg·L-1(IV standard for surface water),the effects of different phosphorus sources and trace elements on the growth and toxicity of M.aeruginosa were investigated under the two phosphorus loading conditions.It was found that under low phosphorus conditions,the interaction of small molecule organic phosphorus and trace elements could significantly stimulate the rapid growth and toxicity of algae.