EFFECTS OF ZIRCONIUM ON THE GROWTH AND PHOTOSYNTHETIC PIGMENT COMPOSITION OF<i>CHLORELLA PYRENOIDOSA</i>GREEN ALGAE

Abstract

The effects of zirconium (Zr) were investigated on the growth rate, dry matter accumulation, and elemental and photosynthetic pigment composition of Chlorella pyrenoidosa green algae. Algae were treated with 0.1–50 μM (≈ 0.009–4.561 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 μM Zr (as Zr ascorbate, a water soluble pH stable chelate) slightly stimulated and 5–50 μM Zr slightly inhibited the dry matter accumulation of Chlorella. Zirconium concentration in the nutrient solution decreased rapidly during the algae propagation, and Chlorella cells accumulated significant amounts of Zr. In the case of 1 μM Zr (Zr ascorbate) treatment, 60.6 μg g−1 Zr was found in the washed cells; after 50 μM Zr application this value was 441 μg g−1 Zr. Zirconium treatment reduced the P, Mg, Cu, and Ti concentrations in algae cells, and the concentration of Fe, Mn, and partly Zn was enhanced. Chlorophyll a, chlorophyll b, xanthophyll, and carotenoid concentrations were equally reduced by 13–33% in Zr-treated cultures. Zirconium treatment changed the chlorophyll a:chlorophyll b ratio and caused appearance of several new chlorophyll derivatives in Chlorella.