Effects of zirconium on the growth and photosynthetic pigment composition of Chlorella pyrenoidosa green algae

The effects of zirconium (Zr) were investigated on the growth rate, dry mat ter accumulation, and elemental and photosynthetic pigment composition of C hlorella pyrenoidosa green algae. Algae were treated with 0.1-50 muM (appro ximate to0.009-4.561 mg dm(-3)) of Zr; inorganic compounds (Zr oxychloride, Zr nitrate) and organic chelates (Zr ascorbate or Zr citrate) were applied . All Zr compounds displayed only a slight insignificant inhibitory effect on the growth rate of algae. Treatment of algae with 1 muM Zr las Zr ascorb ate, a water soluble pH stable chelate) slightly stimulated and 5-50 muM Zr slightly inhibited the dry matter accumulation of Chlorella. Zirconium con centration in the nutrient solution decreased rapidly during the algae prop agation, and Chlorella cells accumulated significant amounts of Zr. In the case of 1 muM Zr (Zr ascorbate) treatment, 60.6 mug g(-1) Zr was found in t he washed cells; after 50 muM Zr application this value was 441 mug g(-1) Z r. Zirconium treatment reduced the P, Mg, Cu, anti Ti concentrations in alg ae cells, and the concentration of Fe, Mn, and partly Zn was enhanced. Chlo rophyll a, chlorophyll b, xanthophyll, and carotenoid concentrations were e qually reduced by 13-33% in Zr-treated cultures. Zirconium treatment change d the chlorophyll a:chlorophyll b ratio and caused appearance of several ne w chlorophyll derivatives in Chlorella.