Growth Competition Between Microcystis Aeruginosa And Chlorella Vulgaris Under Different Nutrient Level

The algae bloom has brought great disaster to human and the ecological system.To understand the competition behavior is beneficial to the control of the algae blooms.In order to know how nutrient influence the results of the competition,the experiments were carried out to research the interspecific competition between Microcystis aeruginosa and Chlorella vulgaris.We mainly researched their growth characteristics and competition behavior at different comprehensive nutrition status(over-eutrophication,eutrophication,below-eutrophication and oligotrophication)and under nitrogen-limitation or phosphorus-limitation,both including uni-culture and co-culture.The indexes analyzed in the experiment are the cell density,the intracellular element content of C?N?P?S,and the consumption of TN(total nitrogen)and TP(total phosphorus).(1)The results indicate that maximum biomass of both Microcystis aeruginosa and Chlorella vulgaris decrease with the decrease of nutrition concentrations in the uni-culture system(under the four nutrition levels,maximum biomass of Microcystis aeruginosa are 2.56×107 cells/mL?3.41×106 cells/mL?1.37×106 cells/mL?0.7×106 cells/mL while the maximum biomass of Chlorella vulgaris are 1.23×107 cells/mL?3.47×106 cells/mL?4.01×106 cells/mL?1.77×106 cells/mL).(2)In co-culture environment,the competitive advantage of Microcystis aeruginosa was observed in super-eutrophication groups,while the competitive advantage of Chlorella vulgaris appeared in other conditions.(3)The intracellular element content of nitrogen and phosphorus declines obviously with the decrease of nutrition level,while that of carbon and sulfur doesn't.From this,we know that N and P are more important for the algae than C and S,when the nutrition level decreases.(4)Furthermore,the Microcystis aeruginosa need more nitrogen than Chlorella vulgaris,while Chlorella vulgaris need more phosphorus than Microcystis aeruginosa.Both the half-saturation constant and maximum specific growth rate of Microcystis aeruginosa are higher than that of Chlorella vulgaris under the nitrogen-limitation.But under phosphorus-limitation,the half-saturation constant of Microcystis aeruginosa is less while the maximum specific growth rate of it is higher.