Statistical study on the effects of environmental factors on the growth and microcystins production of bloom-forming cyanobacterium-Microcystis aeruginosa

In this paper, a systematic investigation on the effects of environmental factors on the growth and microcystins production of Microcystis aeruginosa using statistically based experimental design is presented. The effects of various chemical and physical factors on cell growth and microcystins production were firstly studied in two levels Plackett-Burman design. NaNO₃, K₂HPO₄, iron, light intensity and temperature were screened out to have significant effects (with confidence level above 90%) on cell growth whereas only NaNO₃, iron and light intensity had significant effects on microcystin production. The interactions between the screened variables were then evaluated using central composite design. The analysis of the experimental responses revealed that nitrate and phosphate as well as phosphate and temperature had significant interactive effects on cell growth, respectively, whereas iron and light had significant interactive effect on microcystins production. The critical border values of the variables that may stimulate the rapid growth of Microcystis and microcystin production, when they were simultaneous present in the water, were represented in the second-order polynomial models and determined to be NaNO₃ >1.27 mM, K₂HPO₄ >0.1 mM, iron >0.01 mM, light intensity >26 μmol m^-2 s^-1 as well as temperature >18.8 °C, respectively.