A Study On The Relationship Between The Common Freshwater Diatom Synedra Sp. And Water Quality

Algae and water quality are an interdependent organic whole.The interaction between the two can not only affect water quality,but is also important for maintaining a healthy ecosystem.By studying the relationship between algae and water quality,it can help us quickly understand the health of a certain water body,and it has reference significance for the protection of water quality.In this study,the common diatom in the water was used as the research object.Through the study of the relationship between the diatom and the water nutrition,to understand the mutual influence and dependent conditions of the two,to provide a scientific basis for revealing the growth and extinction of diatoms under natural conditions on changes in water quality.In this study,potassium nitrate was used as the nitrogen source,and dipotassium hydrogen phosphate was used as the phosphorus source.Different nutrient conditions（nitrogen and phosphorus concentration）were respectively treated on the common diatom species-Synedra sp.,and to study the effects of different nutritional conditions（nitrogen and phosphorus concentration）on the physiological process of Synedra sp.The physiological changes and adaptation of the environment provided a scientific basis for water quality safety assessment and management.The research was carried out from the following aspects:1.After treatment with different concentrations of nitrogen and phosphorus,explore its effect on the photosynthetic activity of Synedra sp.and its growth status;2.The inoculation of Synedra sp.with different inoculation densities in the same culture solution to study the effects of its growth on water quality impact,elaborating the impact of the growth of the Synedra sp.on the water quality;3.Under the shading treatment and the nitrogen phosphorus treatment is in the growth state and extinction of Synedra sp..The dynamic change of the water quality further illustrates the relationship between diatom and water quality.The main results are as follows:1.When the nitrogen concentration is in the range of 0-1 mg/L,the cell density and the specific growth rate,Fv/Fo and Fv/Fm of Synedra sp.increased with the increase of nitrogen concentration.On the 2nd,4th,6th and 10th days,the maximum light energy conversion efficiency of Synedra sp.in the treatment group with different nitrogen concentration was significantly different from that of the control group（P<0.01）.However,with the increase of sampling time,the activity of PSII decreased and the maximum efficiency of light utilization decreased on the group with the highest and lowest nitrogen concentration.The ABS/RC and DIo/RC of photosynthesis energy absorption and transmission were significantly different from the control group on the 6th days（P<0.01）,and there was no difference between the TRo/RC and ETo/RC groups（P>0.05）.2.Phosphorus concentration was in the range of 0-0.2 mg/L,and there was no difference between the cell density groups（P>0.05）.The cell density in the treatment group on the 2nd day increased compared with the 0th day.Compared with the control group,Fv/Fo and Fv/Fm of the treatment group had no significant difference on the 2nd day（P>0.05）.On the 4th day,there was a very significant difference between the groups（P<0.01）.ABS/RC,TRo/RC,ETo/RC and DIo/RC in the treatment group were not different from those in the control group（P>0.05）.3.The content of TDP and PO₄⁺-P in the culture of the Synedra sp.in the treatment groups with different initial inoculation densities all showed a downward trend during the sampling period.The contents of TDP and PO₄⁺-P of cells/m L were higher than those of the other two groups on the 12th day.The group with high initial inoculation density had a rapid decline in NO₃^--N content,and the group with low initial inoculation density had small changes in NO₃^--N content.The treatment groups with different initial inoculation densities had no obvious regularity with the TDN,NH₄⁺-N content and p H value,and the trends of conductivity were consistent with cell density.4.The cell density under shading condition was lower than that under non-shading condition.The change in cell density under shading conditions was inconsistent with the change trend of NO₃^--N content,the cell density showed a downward trend,and the NO₃^--N content showed a zigzag change.There was a negative correlation between cell density and NO₃^--N content in culture medium.The cell density at different nitrogen concentrations was inconsistent with the NO₃^--N content in the culture solution.Phosphorus concentration was 0 mg/L and 0.02 mg/L,and the cell density of Synedra sp.is positively correlated with PO₄⁺-P content.Phosphorus concentration was 0.1 mg/L and 0.2 mg/L,and the cell density of Synedra sp.is negatively correlated with PO₄⁺-P.