Adsorption of zinc ions by Scenedesmus obliquus and S-quadricauda and its effect on growth and metabolism

Zinc adsorption by two green algae, Scenedesmus obliquus and Scenedesmus quadricauda, was investigated. The maximum adsorption capability of zinc ion obtained from the Langmuir adsorption isotherms was higher for S. obliquus (6.67) than for S. quadricauda (5.03), and S. obliquus was more tolerant to zinc phytotoxicity than S. quadricauda. Lower concentrations of zinc increased dry mass, chlorophylls a and b, carotenoids, and total amino acid contents in both algae. On the other hand, higher concentrations of zinc were inhibitory for growth and the other metabolic activities in a concentration dependent manner.