Effects Of Nitrifying Bacteria Preparation On The Growth Of Bloom Alga

Bacteria and alga participate in the nutrient recycling and material circulation in aquatic ecosystem. Studying the relationship between bacteria and alga is meaningful to adjust the aquatic ecosystem. This paper studied the effects of nitrifying bacteria preparation on the growth of Microcystis aeruginosa and wild alga in coculturre system. The results of the investigation were as follows:(1) A certain concentration of nitrifying bacteria preparation could inhibit the growth of Microcystis aeruginosa. And the inhibition gradually increased with the concentration of nitrifying bacterica preparation increasing. The algal biomass of the treatment groups (108cells/mL,109cells/mL) decreased by 12.5% and 15.0% separately compared with the same period control after ten days; the initial concentration of alga could affect the inhibition. The higher the initial concentration of alga, the smaller the inhibition.(2) Some environmental factors (culturing temperature, light, pH of culture medium, salinity and dissolved oxygen) could affect the inhibiting effects in different degree. The inhibition was low under high temperature; low-intensity light enhanced the inhibition. The algal biomass (108cells/mL) decreased by 17.2% compared with the same period control after ten days under 500lux; the inhibition was low under slightly alkaline condition or high dissolved oxygen; there was no inhibition under high salinity.(3) Nitrifying bacteria preparation had a certain impact on the dissolved oxygen, turbidity and Chla of water bloom. Concentrations of nitrifying bacteria preparation could differ the effects. The water became clear, and the turbidity and Chla both decreased after adding nitrifying bacteria preparation of 107cells/mL and 108cells/mL. The effects were much better under high concentrations of nitrifying bacterica; the water became clear after adding nitrifying bacteria preparation of 109cells/mL. There was much light into the water promoting the growth of alga. The dissolved oxygen was also higher than the control obviously.(4) Nitrifying bacteria preparation affects the growth of Microcystis aeruginosa in indirect mode. The inhibiting factor may be the extracellular material of nitrifying bacteria or the intermediate of nitrification. And the inhibiting factor has poor thermal stability.