重金属铅与两种淡水藻的相互作用

Interactions between heavy metal lead and two freshwater algae

为了研究重金属铅与淡水藻类之间的相互作用,采用不同Pb2+浓度处理铜绿微囊藻(Microcysis aeruginosa Kutz.)和斜生栅藻[Scenedesmus obliquus(Turp.)Kutz.],分别对两种藻的生物量、藻液电导率、O-·2含量、过氧化物酶(POD)、过氧化氢酶(CAT)活性以及藻对Pb2+的吸收作用等进行了测定,并通过扫描电镜观察了不同Pb2+浓度处理下两种藻细胞的表面结构。结果显示:(1)Pb2+浓度低于3 mg/L促进铜绿微囊藻生长,高于9 mg/L抑制其生长;但在3—12 mg/L范围内,Pb2+均明显抑制了斜生栅藻的生长,说明斜生栅藻对Pb2+毒性的敏感程度要高于铜绿微囊藻。(2)受到铅离子的胁迫,两种藻细胞膜通透性均有一定改变,扫描电子显微镜的照片观察,两种藻细胞表面的絮状物随着Pb2+的升高而增多,尤其是斜生栅藻细胞结构改变明显,多数细胞变形破裂;同时,O-·2含量升高,POD、CAT活性早期均可随Pb2+的增加而上升,表明氧自由基的产生增多以及由其引起的细胞生理生化改变可能是铅离子作用于藻细胞的主要机制。(3)两种淡水藻对Pb2+均有吸收作用,单位量藻细胞内,斜生栅藻对Pb2+的吸收能力好于铜绿微囊藻。所有结果提示:斜生栅藻不仅可以作为对重金属敏感的指示生物来监测水体Pb2+污染程度;同时由于斜生栅藻比铜绿微囊藻具有更好的Pb2+吸收能力,因此还可以利用斜生栅藻作为处理水体Pb2+的生物材料。

To get a better understanding of interactions between heavy metal lead and freshwater algae Microcysis aeruginosa Kutz. and Scenedesmus obliquus （Turp.） Kutz., the algal biomass, electrical conductivity （EC） of supernatant, concentration of superoxide anion radical （ O2- ）, activities of POD and CAT as well as the absorption of Pb2＋ by algal were determined respectively at different concentrations of Pb2＋, and the surface structure of two algae cells was contrasted by scanning electron microscopy. The results showed as follows ： （ 1 ） 3 mg/L of Pb2＋ accelerated the growth of M. aeruginosa, and the opposite effects were observed when exposed obviously inhibited when the concentrations of Pb2＋ to more than 9 mg/L of Pb2＋ ; however, the growth of S. obliquus was ranged from 3 to 12 mg/L. The effects of Pb2＋ on the two kinds of freshwater algae indicated that S. obliquus was more sensitive to the Pb2＋ pressure. （2） The membrane permeability of the two algae cells was changed under the stress of Pb2＋. The photos of scanning electron microscopy showed that the superficial flocs of the two algae ceils increased with the increasing of Pb2＋, and numerous cells deformed or ruptured evidently, especially for S. obliquus. Meanwhile, the increases of O2 contents were exhibited and the activities of POD and CAT in the two algae were advanced with increasing of Pb2＋ concentration at the early stage, which indicated that the main mechanisms of Pb2＋ acting on two algae involve the increasing production of superoxide anion radical and the accompanying physiological and biochemical changes of the algae. （ 3 ） Pb2＋ can be absorbed by the two algae, and moreover S. obliquus had higher capacity of Pb2＋ absorption than M. aeruginosa did at the unit cells. From the above points, compared with the M.aeruginosa, S. obliquus can be used not only as a biological indicator for monitoring heavy metal pollution levels, but also as a biological material to deal with water Pb2＋ contamination due to its ability of Pb2＋ absorption.