Sensitivity of freshwater microalgal strains (Chlorella vulgaris Beijerinck and Scenedesmus obliquus (Turpin) Kutzing) to heavy metals

Microalgae are a valuable environmental and biotechnological resource, and the aim of this paper is to explore the use of in vitro technologies in the conservation and sustainable exploitation of this remarkable group of organisms. Microalgae are sensitive indicators of environmental change and, as the basis of most freshwater and marine ecosystems, are widely used in the assessment of risk and development of environmental regulation for metals. The microalgae genus Scenedesmus and Chlorella are commonly found in freshwater bodies, wastewater facilities and water polluted with heavy metals. The sensitivity of two freshwater microalgal species (C. vulgaris and S. obliquus) to two heavy metals Ph (II) and Cd (II) was studied by using BG11 media. The individual effects of cadmium and lead on the cell division rate of the freshwater alga C. vulgaris and S. obliquus were determined over 24 to 96 h. Heavy-metal EC50 values after a 48-h exposure in S. obliquus were (EC50:13.71 mg/L for Cd, EC50: 4.04 mg/L for Pb) and C vulgaris (EC50:28.41 mg/L for Cd, EC50: 24.50 mg/L for Pb) and both are more tolerant to Cd. A good linear relationship was observed between the media type and tolerating toxicity. According to this research these strains have a high level of tolerance to heavy metals. Heavy metals, especially cadmium and lead have adverse effects on terrestrial and aquatic environments. However, their impact can vary depending on the nature of organisms.