Effects of neodymium on growth and physiological characteristics of Microcystis aeruginosa

To investigate the effect of neodymium (Nd) on Microcystis aeruginosa, the growth and physiological changes were studied by lab cultured experiments. The results showed that the content of chlorophyll a (Chl-a), soluble protein and the activity of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) increased compared with the control (Nd3+-free), and the growth of M. aeruginosa was stimulated in the treatments of initial Nd3+ concentration ≤1 mg/L; while the treatments of initial Nd3+ concentration was in the range of 5.00-10.00 mg/L, the content of malondiadehyde (MDA) increased immediately but the activity of CAT reduced, which resulted in weakened M. aeruginosaʹs ability to eliminate the active oxygen and the ruin of antioxidant defense system, and stunting the growth of M. aeruginosa. With the initial Nd3+ concentration of 50 mg/L, the growth of M. aeruginosa was totally stunted. The ultrastructure showed that excess Nd3+ could lead to the decrease of thylakoid and the increase of fat particle in cells of M. aeruginosa, and the cell membrane became rough and even broken, causing an irreversible damage to algal cells.