Effects of Zn and Mn on Population Dynamic, Chlorophyll a and Caroteniods in green microalgae Scenedesmus quadricauda

Aquatic environments are often received to industrial, agriculture and domestic effluents containing metals and caused biological problems for microalgae because they require to some of essential trace elements. In this research, solely effects of different concentrations of Zn (450, 900 and 1350 mg/l) and Mn (75, 150 and 225 mg/l), and their combined effects (450, 900힝, and 1350� from Zn in mg/l) on some physiological parameters of population dynamic, growth, chlorophyll and carotenoid contains in green microalgae Scenedesmus quadricauda were investigated under laboratory conditions of temperature of 22±2 ºC, photoperiod of 12 hours light : 12 hours dark, and light intensity of 80 µmol photons/m2/s. The experiment was carried out as completely randomized design with three replications for a 22 days period. Results showed that the peak of population density obtained at 900 mg/L of Zn, 150 mg/l of Mn and their combination 900힝 mg/l of Zn. The maximum growth rates were 0.060, 0.058 and 0.056 /day for Zn, Mn and their combination, respectively. The minimum doubling time of population attained 11.6 days at 900 mg/l of Zn. The maximum chlorophyll a and total carotenoid were 1.8 and 93.2 mg/L, respectively, at 900 mg/L of Zn which had significant differences with other treatments. The findings of this study showed that increasing of Zn until 900 mg/L and Mn until 150 mg/l that resulted to improving of population, growth, chlorophyll a and total carotenoid in the S. quadricauda. As conclusion, this study illustrated that changing of Zn concentration in BBM medium had significant effects on cell density, chlorophyll a and total carotenoid. In addition, the Zn effects on physiological characters were higher than Mn and its increasing to concentration of 900 mg/l caused improving them in S. quadricauda.