Study Of Toxic Effects Of Single And Combined Pollution Of Glyphosate And Cu²⁺ To Nizschia Palea

The research of combined pollution in water environment in the past is mostly about phytoplankton to different kinds of diatoms. But there are few reports about combined pollution between heavy metals and pesticides to benthic algae.The habitat of benthic algae is not like phytoplankton so the response of two kinds of algae to stressors may not same. So find the response of benthic algae to heavy metals and pesticides can help us to understand the effects of stressors to water environment in more comprehensive view and the effects to benthic producer.In this research, two purified diatom（Nitzschia palea and Achnanthes sp.）, which is purified using a improved separating method, was selected and the motility of 2 kinds of diatoms was studied. Through acute and subacute toxicity test, survival number of N. palea was recorded under LM and the speed, the moving path was also be logged by a software image J and the submicroscopic structure of N. palea was taken by SEM. The possibility of monitoring water ecology was also discussed in this research.The results of the research is as follows:Using capillary tube method, water-drop method, streak plate method, and the combined method, 4 kinds of diatom was purified. The advantage of each method was analyzed. capillary tube method need very high technique and the survival rate of this method is low but the pure rate in survival individuals is very high, achieve 70% and this method is apply to purify big size diatoms. Water-drop method had a quite low separation rate,5%, and the pure rate in survival individuals was also low, 15% but the method has a big superiority quick operating speed. Streak plate method is very simple and have very high survival rate（60%） and pure rate in survival individuals（40%） but the circle of this method is very long. The combined method is combined by water-drop method and streak plate method and also combined the advantage of the 2 methods.The moving paths of two diatom, N. Palea and A. Sp., were recorded by Image J. There were huge difference between the moving path 2 diatoms. The path of N. Palea was circle and A. Sp. was like a line. The speed of N. Palea and A. Sp. is 9.09 μm/s and 2.73μm/s respectively. The tendency of the the speed of 2 diatom was just like the rate of moving diatoms in all diatoms, which was turn down over time and reach stable state at 6th to 7th day. For N. palea, the rate of moving diatoms in all diatoms at stable state was 20%, and the speed was about 6 μm/s. For A. Sp., the rate of moving diatoms in all diatoms at stable state was 35%, and the speed was about 1.5 μm/s. And the content of EPSs was increased during the culturing.Glyphosate was used to stress N. Palea in acute way and subacute way.In acute toxicity test, I found the 96 h EC50 of N. Palea to glyphosate was 55.92 mg/L. In low concentration glyphosate could improve the growth of N. Palea and the concentration which improve the growth of diatom most was 3 mg/L, and under high concentration the growth of the diatom was restrained.In subacute toxicity test,through compare with reference group,rate of moving diatoms in all diatoms and speed of diatoms was turn down. I also found submicroscopic structure deformity rate turn high under the subacute stress by SEM. The main deformity were areolar deformity and one more valve when diatom was fissuring.Cu²⁺ was used to stress N. Palea in acute way and subacute way.In acute toxicity test, I found the 96 h EC50 of N. Palea to Cu²⁺ was 1.28 mg/L. In low concentration Cu²⁺ could improve the growth of N. Palea and the concentration which improve the growth of diatom most was 0.05 mg/L, and under high concentration the growth of the diatom was restrained.In subacute toxicity test,through compare with reference group,rate of moving diatoms in all diatoms and speed of diatoms was turn down dramatically.When N. Palea was stressed by glyphosate and Cu²⁺ joint pollution, I found the inhibition ratio of joint stress was bigger than the inhibition ratio of solo stresses but smaller than the sum of inhibition ratio of two single pollutant.The conclusion of the thesis are as follows:1.The toxicity of glyphosate to N. Palea is middle-toxic,and can effect their motility and can cause malformation;The toxicity of Cu²⁺ to N. Palea is high-toxic,and can effect their motility seriously.2.The combined toxcity of glyphosate and Cu²⁺ to N. Palea is partly additive synergism.3.The combined method is the most suitable way to purify small diatom.4.The moving speed and path of diatoms depend on the length and the location of the raphe. And both N. Palea and A. sp. are turned to live in surrounding of EPSs statically.