Abstract: Mirco-nutrients exert significance impacts on fresh water plankton biomass. Through orthogonal experiments the promoting effects of typical micro-nutrients(P, Fe, Mn and Zn) on algae bloom organisms(Cyanobacteria) were are studied. The experimental results obtained show that the algae biomass had has a linear increasing relationship with the concentration of phosphorous (ranging from 0.04~0.32 mg/L). Algae growth rate was is promoted at with the concentration below Fe(0.05 mg/L) and Zn(0.01 mg/L), while it is was inhibited at with the concentration above Fe (0.1 mg/L) and Zn(0.04 mg/L). Manganese(Mn) showed has no regularity obvious influence on algae biomass and algae growth rate., It is possible to stimulate algae growth with concentration of Mn below than 0.05 mg/L or above than 0.1 mg/L. The results show that phosphorous had has no effect on algae growing cycle, while there is a direct proportion between the concentrations of iron, manganese and zinc and the lag phrase of algae. Mn and Zn show no impact on algae community structure, but high Fe is beneficial to Cyanobacteria.
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Key words: micro-nutrients; growth rate; biomass; dominant species; growth period