Study On The Toxic Responses Of Freshwater Algae To Copper Pollution In Water Column

With the discharge of industrial sewage and domestic wastewater, the heavy metalpollution of water column has become a global environmental pollution question. Asthe primary producers of water ecological system, the community structure andcomposition of algae is closely related to water environment. So we can monitor thepollution of the water by analyzing species and quantity of the algae, and all kinds ofphysiological indexes. In this paper, the response to the toxicity of the copper pollutionin phytoplankton and attached algae had been investigated, and we try to validatephysiological parameters in the algae as biomarkers of heavy metal pollution. Thus itprovides a simple and sensitive method for monitoring and warning the heavy metalpollution of water column. The main results were showed as follows:(1) Different species of algae had different responses to the stress of the heavymetal. The celluar algae in smaller size were more sensitive on copper pollution, whilethe celluar algae in bigger size were more tolerant to heavy metal stress.(2) The influence on physiological indices of the algae lied on the concentrationof copper. When the concentration copper was low, it produced less toxic effects; butwith the increase of the concentration of heavy metal stress, the degree of the damagewould be getting more and more serious. The mechanisms of copper toxicity and theresponse of mechanisms of algae in fresh water were：Under the stress of lower copperconcentration, algae can could scavenge the excessive radical oxidative species (ROS)by themselves,with the increase of stress concentration, the secretion of extracellularpolymeric substances(EPS) increased, and the ability to scavenge radical oxygen species (ROS) including·O^2-,·OH enhanced quickly. EPS could strengthen thecapacities of antioxidative system scavenge the excessive ROS, and consequentlyprevent the cell from injury. However, with the increase of duration and concentrationof metal stress to some extent, the activity of antioxidative system would decline, andthe scavenging of ROS was out the range of the capacities of antioxidative system,which may result in the destruction of the cellular structure, the weakening ofchlorophyll fluorescence intensity, the degradation of chlorophyll content, the celllipid peroxidation strength enhanced, the reinforcement of lipid peroxidation ofmembrane, accumulation of MDA, eventually lead to the obstruction ofphysiological function of the algae and ultimately death.(3) The result showed that the variation of MDA, SOD and Vc all could reflectthe pollution of heavy metal to freshwater, and can be used as biomarkers forpredicting heavy metal pollution of the water column.(4) When monitoring the toxicity of copper pollution by biomarkers ofphytoplankton and attached algae, the two methods of each have an advantage. Theformer had better liquidity and smaller size, which was more sensitive to heavy metalpollution of water column. The latter was not easy to migration, which was morestability to the pollution monitoring. So combining both of them can give quickresponse to pollution, which can help improve the accuracy of monitoring and warningof heavy metal pollution, and therefore was significant in predicting and monitoringthe heavy metal pollution of water column.