Effects of Hg~(2+) Exposure on the Growth and Chlorophyll Fluorescence of Three Microalgal Strains

The present study investigated the growth and chlorophyll fluorescence characteristics of 3 microalgal strains(Chlorella pyrenoidosa,Scenedesmus obliquus and Chlamydomonas reinhardtii) under different Hg2+ concentrations and different durations(1-7 d).The main parameters including the maximal photochemical efficiency of PSII(ΦM),the relative electron transport rate(rETR),the saturation intensity(Ik)and cell density were determined.The results showed that the chlorophyll fluorescence and cell density of 3 microalgal strains all exhibit some correlations to Hg2+ concentration and exposure duration.While cell density has very significant positive correlations(P0.01) to fluorescence parameters.Comparison of the EC50 values of different exposure durations among the 3 algal species indicated the ability of their tolerance to Hg2+ was S.obliquusC.reinhardtiiC.pyrenoidosa.