The Toxicological Effects Of Pb²⁺ On Chlorella Vulgaris And Chlorella Protothecoides

Lead is one of the most serious pullutants in the environment, It showed large distribution range and persistent toxic. Microalgae are often used as environmental pollutant sensitive indicator in today’s research, but the research about the toxicological effects of Pb2+on the microalgae is very little and so chooses Chlorella vulgaris and Chlorella protothecoides for pollution biological indicators. Under the constant temperature, humidity and light cycle periods, the aquatic ecological toxicological effect of Pb2+to both kinds of Chlorella’s physiological, biochemical and photosynthesis-related functional genes exposure to different concentrations and poisonous periods. Thereby provide science basis for science evaluate the aquatic ecological risk of Pb2+. The main research results are showed as follows:(1) It is very sensitive that Chlorella vulgaris and Chlorella protothecoides exposed to Pb2+and showed dose--ependent and time-dependent effect, the increments of processing groups of both algae were lower than those of the control groups; And in chronic toxicity experiments. Both algae could recover to normal growth after28d when exposed to low concentrations of Pb2+(1and5mg/L), but both algae can’t recover when exposed to high concentrations (50and80mg/L).(2) The MDA contents of Chlorella vulgaris and Chlorella protothecoides were promoted by Pb2+concentrations, MDA contents of the all treatment groups were higher than those of control groups, but on the whole experiment, MDA contents of chronic toxicity of the treatment groups were lower, and MDA contents of both algae were showed similar tendency.(3) Chlorophyll a synthesis of Chlorella vulgaris and Chlorella protothecoides were significantly inhibited by Pb2+. The impacts of lead to chlorophyll a synthesis of both algae and the rule of exposure time extension were consistent with the growth.(4) SOD and CAT activities of Chlorella vulgaris and Chlorella protothecoides were similar when exposed to different concentrations of Pb2+. The enzyme acitivity of both algae are increase when exposed to low concentrations of Pb2+, but decrease by higher concentrations. Antioxidation enzyme systems of both algae were destroyed by lead and affect the normal state equilibrium of the reactive oxygen species of both algae between produce and clear.(5) Three kinds of photosynthesis-related functional genes of Chlorella vulgaris and Chlorella protothecoides were inhibited by different concentrations of lead. Three kinds of genes expression quantity are inhibited by Pb2+, but exposure to80mg/L Pb2+, the relative amount of three kinds of gene expression in chronic toxicity experiments are lower than in acute toxicity experiments.