Effects Of Different Concentrations Of Different Metals On The Growth And Chlorophyll Fluorescence Characteristics Of Microcystis Aeruginosa And Scendesmus Obliquus

Algae, major primary producer in body of water, play an important role in the aquatic ecosystem. The study of the interations between algae and heavy metals was of importance for bioassay of toxic metals and the biotechnology to remove metals from wastewater. The growth and chlorophyll fluorescence traits of M. aeruginosa and S. obliquus exposed to the culture medium(BG11) with different heavy metals concentration for different times (12,24,48,72and96h) were studied. The main parameters determined in the study included cell density (A650nm,A670nm) of M. aeruginosa and S.obliquus, the maximal photochemical efficiency of PS Ⅱ (Fv/Fm), the actual photochemical efficiency of PS Ⅱ in the light (ΦPS Ⅱ=Yield), the potential activity of PS Ⅱ (Fv/Fo), the maximal relative electron transport rate (Pm, rETRmax), light use efficiency(a) and semi-light saturation point(IK). The results were showed as follow.1.Under the lower concentration, the growth of the M. aeruginosa (S. obliquus) would not be obstructed by the three heavy metals, especially when the concentrations of Cu2+, Zn2+, Mn2+were lower than10μmol·L-1(0.5μmol·L-1),10μmol·L-1(0.1-1μmol·L-1),10-100μmol(L-1(1-5μmol·L-1). But the growth of the two algae were promoted under the concentrations of Zn2+(2-4μmol·L-1) and Mn2+(10-100μmol·L-1).2.The trend of chlorophyll fluorescence was similar to the growth. Under the lower concentration, the growth of the M. aeruginosa(S. obliquus) would not be obstructed by the three heavy metals, especially when the concentration of Cu2+, Zn2+, Mn2+were lower than10μmol·L-1(0.5μmol·L-1),10μmol·L-1(0.1-4μmol·L-1),10-100 μmol·L-1. However, the photosynthesis of M. aeruginosa severely was promoted by the lower Mn2+concentration(1-100μmol·L-1).3.The results of growth and chlorophyll fluorescence of the two algae at the time of48h and96h showed that the toxicity results could be expressed as Cu2+> Zn2+> Mn2+under the concentrations of the three heavy metals.4.The tolerance of Cu2+and Zn2+of Scendesmus obliquus would be larger than that of M. aeruginosa, but the Mn2+tolerance between them was similar.5.In addition, the whole trend of chlorophyll fluorescence of the two algae was different after the treatment of three heavy metals. To be specific, the chlorophyll fluorescence of M. aeruginosa decreased at the initial period and then increased, however, which of Scendesmus obliquus showed a decreasing tendency. And the parameter Pm was affected by the three metals larger than additional parameters.