The Relationship Between Environment Factors And The Growth Of Microcystis Aeruginosa And Its Toxicology Under Cu～(2+) Stress

A strain of bloom cyanobacterium (blue-green alga), Microcystis aeruginosa, which dominated in an eutrophic pond, was isolated and purified for physiological study in laboratory conditions.Various environment factors, like light, temperature, nutrient, Cu2+, ect were tested for growth and lexicological effects of M.aeruginosa.The results of research about the effect of light, temperature and nutrient on the growth of M.aeruginosa are as follows:1.BG11 was proved to be the most suitable medium for the purified strain of M.aeruginosa. Moreover, with some nutrient combinations of 0.01ug.mL-1 2, 4-D,20g.L-1 glucose and 100ug.mL-1 acetic sodium in the BG11 medium, it was observed that the growth of M. aeruginosa was speeded up and the stationary period of it was shortened evidently.2.0n conditions of abundant phosphorus, ammonium in concentration below 2.54mg.L-1 could limit the growth of M.aeruginosa, that ranging from 7mg.L-1 to 15mg.L-1 triggered the growth of M.aeruginosa, and that above 19.25mg.L-1 would inhibit its growth.3.The favorable light intensities for M.aeruginosa growth were in the range from 3500Lx to 7000Lx,and the most favorable light intensity was around 5000Lx.4.The suitable temperatures for the growth of M. aeruginosa were from 28℃ to 33℃,and the most favorable temperature was 30℃.The results of changes in resistant and toxicological effects under Cu2+ stress are as follows:1.Ranging from 10-2M to 10-5M,Cu2+ presented inhibitory effect on the growth of M.aeruginosa, moreover, the greater the concentration of Cu2+, the more intensive the inhibitory effect on the growth of M.aeruginosa. In contrast, Cu2+ below 10-5M would be favorable to the growth of M.aeruginosa.. The most favorable concentration of Cu2+ for its growth was 10-6M.2.Cu2+ in lower concentrations(10-6~10-7M) did not show inducible effect, butas a trace element, it presented the stimulating effect for the growth of M.aeruginosa,Cu2+ in mid-concentrations(10-4~10-5M) would induce the SOD activities to rise, whereas Cu2"1" in higher concentrations(10-2~10-3M) would poison the cells and displayed the inhibitory effect for the growth of M.aeruginosa.3.Cu2+ at 10-5M appeared to induce M.aeruginosa to produce the most amount of MTL, Cu2+ at 10-6M would induce the moderate amount of MTL to be yielded, but Cu2+ at 10-3M showed obviously inhibitory effect on the growth of M.aeruginosa, and the amount of induced MTL was the least. Again, the yield of MTL reached the maximum within the period of 6~9 days. Moreover, the resistant strain of M.aeruginosa could produce more MTL than the non-resistant strain under the same conditions.4.The decrease of Cu2+ in BG11 medium was observed to mainly took place before 24h.The resistant strain accumulated the maximal Cu2+ at 24h.The removal ratio of Cu2+ at 24h in BG11 medium was 48.87%, and it was 80.77% at 96h.But as to the non-resistant strain, the respective biodegradation ratio of 24h and 96h are 20.88% and 34.29%.