INFLUENCE OF TRIVALENT AND HEXAVALENT CHROMIUM ON 2 CHLORELLA STRAINS

The influence of several Cr compounds (0-2 mg Cr/l as KCr(SO4)2, Cr(III)-EDTA, CrLIII)-glycine, or K2Cr2O7) were studied with the unicellular green algae C. pyrenoidosa 211-8b and Chlorella WR 1, the latter being a wild strain isolated from a Cr-polluted surface water. The algae were cultivated either in permanent light or under a light/dark regime (16:8 h). Several distinct effects of the trace metal on algal metabolism were detected. At low Cr concentrations (0.1-0.5 mg Cr/l) stimulation of growth and photosynthetic O2 evolution, a general depression of chlorophyll synthesis and an acceleration of cell division, paralleled by a decrease in cell volume, were found. Some of these effects were not always expressed in the wild strain; this alga was less influenced by Cr(III) under light/dark changing conditions. The effect of adaptation of Chlorella WR 1 to its natural environment upon Cr toxicity is discussed.