Growth and Physiological State of Microalgae Heterosigma akashiwo (Raphidophyceae) during Exposure to Cadmium, Lead, and Nickel

Abstract

The effect of heavy metals cadmium, lead, and nickel on the growth and physiological state of raphidophyte algae Heterosigma akashiwo MBRU_HAK-SR11 (Y. Hada) Y. Hada ex Y. Hara, M. Chihara during 7 days of experiments has been assessed. It was found that cadmium and nickel at concentrations of 10 and 20 µg/L stimulated H. akashiwo growth, while lead inhibited it at these concentrations. Chlorophyll a and carotenoids content increased with the addition of 10 μg/L of cadmium and 20 μg/L of nickel, and the content of carotenoids was higher than that in the control with the addition of 20 μg/L of cadmium. With the introduction of lead, an increase in the level of chlorophyll a and a decrease in the content of carotenoids were observed. The content of ROS increased with the introduction of cadmium and lead and decreased with the introduction of nickel. Cadmium had an effect on the production of neutral lipids: their content increased and decreased by the end of the experiment. Nickel stimulated the accumulation of neutral lipids H. akashiwo, while lead had no effect on their content. Metals had the least effect on forward and side light scattering and fluorescence of chlorophyll a. The absence of pronounced changes in direct and lateral light scattering indirectly indicates that the algae cells did not change morphologically under toxic exposure. Thus, cadmium, lead, and nickel at concentrations of 10–20 µg/L changed physiological processes in algae.