镉对铜绿微囊藻和斜生栅藻的毒性效应

采用不同Cd2+浓度处理铜绿微囊藻(Microcysis aeruginosa Kutz. )和斜生栅藻[Scenedesmus obliquus (Turp.) Kutz.],研究Cd对两种淡水藻的毒性效应.结果表明,Cd2+浓度低于0.1mg/L促进斜生栅藻生长,高于0.15mg/L时才转变成抑制作用,表现为毒物的低浓度促进高浓度抑制的Hormesis效应;但铜绿微囊藻对Cd2+的毒性非常敏感,0.05mg/L Cd2+作用72h后,其生长就受到明显抑制,随着浓度的升高,抑制作用越明显;受到Cd2+的胁迫,两种藻细胞均表现为细胞膜受损,藻液可溶性蛋白质和核酸含量升高,扫描电子显微镜观察显示,藻细胞表面的絮状物随着Cd2+的升高增多,尤其是铜绿微囊藻改变更为明显;同时,氧自由基( )含量升高,过氧化物酶(POD),过氧化氢酶(CAT)活性早期均可随Cd2+浓度的增加而上升;两种藻对Cd2+均有一定吸收作用,单位藻细胞内,斜生栅藻对Cd2+的吸收能力明显好于铜绿微囊藻.镉对这两种藻的毒性机制之一可能是通过刺激氧自由基产生以及由其引起藻细胞生理生化改变而使这两种藻受到损伤,相比铜绿微囊藻,斜生栅藻不仅对Cd2+胁迫具有较好的耐受性,且对其具有良好的吸收作用,提示斜生栅藻具有开发成水体Cd2+生物处理材料的潜质.

Toxic effect of cadmium on Microcysis aeruginosa and Scenedesmus obliquus

Toxic effect of cadmium on Microcysis aeruginosa Kutz. and Scenedesmus obliquus (Turp.) Kutz were researched by using different concentrations of Cd2+. The results showed the growth of S. obliquus was accelerated in Cd2+ concentration of 0.1mg/L, and decreased in Cd2+ concentration over 0.15mg/L. Toxicant could promote the growth at low concentration while restrain at high concentration, which might be an effect of hormesis. But M. aeruginosa was more sensitive to Cd2+ with the growth obviously inhibited when the concentrations of Cd2+ were 0.05mg/L and treat 72h, and the inhibitory effect was obvious with increasing Cd2+. The membrane permeability of the two algae changed under the stress of Cd2+, and protein and nucleic acid contents of two freshwater algae rose up. The photos of scanning electron-microscopy showed that the superficial flocs of algae increased with the rise of Cd2+ concentration, especially for M. aeruginosa. Meanwhile, contents raised and the POD and CAT activities in the two algae all increased with the rise of Cd2+ at the early stage. The two algae could absorb Cd2+, and S. obliquus had more adsorption ability than M. aeruginosa at the unit cell. The results indicated that the main toxic mechanisms of Cd2+ imposing on two algae involved the superoxide anion radical generation that induced the physiological and biochemical changes of the algae, and hurt the algae. Compared with the M. aeruginosa, S. obliquus not only had a better tolerant of Cd2+, but a better adsorption ability of Cd2+. It indicates that S. obliquus has the potential of being a biological material to deal with water Cd2+.