Effects Of The Ratio Of Nitrogen And Phosphorus Concentration On Growth And Microcystin Of Microcystis Aeruginosa

In recent years,with the rapid development of economy and frequent activities of human beings,nutrient such as nitrogen and phosphorus have greatly entered the natural water body,which accelerated the process of water eutrophication,and outbreaks of cyanobacteria bloom.Microcystis aeruginosa(M.aeruginosa)is the dominant algae species in most eutrophication water bodies of China,the microcystins(MCs)caused by M.aeruginosa has become an increasingly concerned environmental problem.In this paper,the effect of inoculation amount,nitrogen,phosphorus,culture temperature and culture light intensity on the growth of M.aeruginosa and MCs production were studied,the results showed that:In the cultures with only nitrogen source or phosphorus source,the growth of M.aeruginosa was inhibited,the maximum biomass was only 1.92×10~6cells/m L,which means that the growth of M.aeruginosa was not only determined by nitrogen or phosphorus,both of them affected its growth.In the cultures with nitrogen and phosphorus simultaneously,the maximum biomass was about 10.47×10~6cells/m L at N/P of 10,while the maximum intracellular microcystins(IMCs)was 28.59 fg/cell at N/P of 5.When the N/P ranged from 1:1 to1:10,the phosphorus concentration had little effect on the growth of algal cells,and the maximum biomass was about 6.70×10~6cells/m L.The effect of inoculation amount on the biomass and specific growth rate of M.aeruginosa was limited.The IMCs was almost 13.1fg/cell with the inoculation amount ranged from0.5×10~5to 2.5×10~5cells/m L.When the culture temperature was 30?at N/P of 5,the growth of M.aeruginosa was enhanced,and the maximum biomass was 14.12×10~6cells/m L,and the temperature was positively correlated with algal cell density(P=0.01,R=0.621).Temperature and nitrogen concentration have good superposition effect on promoting algal cell growth.However,the maximum IMCs content was 29.30 fg/cell at the culture temperature of 20?and N/P of 5,and the culture temperature was negatively correlated with the IMCs content(P=0.013,R=0.818).The superposition of temperature and nitrogen concentration on IMCs synthesis was not obvious.When the culture light intensity was 4000 lx at N/P of 10,the growth of M.aeruginosa was enhanced,and the maximum biomass was 11.59×10~6cells/m L,the light intensity was positively correlated with algal cell density(P=0.018,R=0.668).The superposition effect between light intensity and nitrogen concentration was obvious.However,However,the maximum IMCs content was 30 fg/cell at the light intensity of4000 lx and N/P of 5,The light intensity of culture was positively correlated with the content of IMCs(P=0.002,R=0.96).The superposition effect of light intensity and nitrogen concentration on promoting IMCs was not obvious.