Physiological and biochemical response of Dunaliella salina to cadmium pollution

The present study investigates the growth of Dunaliella salina as influenced by cadmium (Cd) contamination. Growth was measured in terms of cell number and chlorophyll a content and was found to decrease with increasing Cd concentration. This metal, which was mainly removed by bioadsorption to cell surfaces (95.34 +/- 3.04 % of total Cd removed), also drastically reduced the soluble and insoluble carbohydrate (0.41 +/- 0.01 and 0.81 +/- 0.07 pg cell(-1), respectively, for 150 mg Cd L-1) concentrations and increased the total metallothioneins protein content (from 0.11 +/- 0.02 for the control culture to 3.30 +/- 0.2 for 100 mg Cd L-1). In addition, the presence of this metal in the medium stimulated the synthesis of some secondary metabolites such as polyphenols, flavonoids, and carotenoids. These compounds had an important role to protect D. salina against the reactive oxygen species (ROS) generated by the presence of Cd in the medium as shown by the increase of the antioxidant capacity of D. salina exposed to Cd.