Effect of HCO_3~- on growth characteristics and competitive behaviors of Microcystis aeruginosa, Scenedesmus quadricauda and Cyclotella sp.

HCO3- is one of the important carbon resources for algaes in lakes. The changes of its concentration in water body have great effect on formation of dominant algaes. Microcystis aeruginosa, Scenedesmus quadricauda and Cyclotella sp. were examined in HAC which included HCO3- in culture medium and in HA without HCO3- in this artical. Growth curves of this three algaes in monoculture were fitted by logistic growth-model respectively. The max specific growth rate r of those algaes were carried out. While competitive parameters were calculated with Lotka-Volterra competition model. The max capacity K and max growth rate r of M. aeruginosa and S. quadricauda in HAC were lager than in HA without reference to pure or mixed culter. It indicated that the growth of M. aeruginosa and S. quadricauda need HCO3- as carbon source to balance its C∶N∶P ratio. Cyclotella sp. could not survive in HAC. M. aeruginosa and S. quadricauda whose mutual inhibiting effect were equal were coexist in HAC. The competitive ability of M. aeruginosa was higher in HA than HAC. The inhibiting effect of M. aeruginosa on S. quadricauda was 1.6 times than reverse and on Cyclotella sp. was 61 times than reverse. The competitive ability of S. quadricauda was weaker than M. aeruginosa and stronger than Cyclotella sp. The inhibiting effect of S. quadricauda on Cyclotella sp. was 10 times than reverse. Cyclotella sp. was eliminated in competition experimentations in HA.