Membrane Fixation Identification Method And Its Application In The Identification Of Phytoplankton In Natural Water Bodies

In order to solve the problems of Lugo’s liquid fixed sedimentation method recommended by China’s lake monitoring and other standards,the sedimentation environment restrictions are large,the sedimentation process is long,the loss of phytoplankton is large and the transportation cost is high,a new method for rapid fixation and identification of phytoplankton-membrane fixation identification method is proposed,and the reliability of the method is verified.In this paper,the membrane fixation identification method and the Lugo’s liquid fixation sedimentation method are compared,and the reliability and applicability of the membrane fixation identification method are verified by detecting the phytoplankton prepared indoors and different natural water samples in the wild,and the method is applied to the study of the community structure changes and succession laws of phytoplankton in the Xiangxi River,a typical tributary of the Three Gorges Reservoir Area,and its main conclusions are as follows:(1)The concentration gradient water samples were prepared by using the phytoplankton mother liquor with higher concentration in culture,and the concentration counts were counted by the Lugo’s liquid fixed sedimentation method and the filter membrane fixation identification method,respectively,and the results showed that 7 phytoplankton and 32 genera were identified by both methods,but the average and minimum values of phytoplankton species detected by the membrane fixation identification method at different concentrations were larger,reflecting the advantages.There was no significant difference in the abundance at the gate level except for the naked algae,and there was no significant difference in the abundance of phytoplankton at the level within the relative abundance of 99%,but the degree of fluctuation and standard error of the membrane fixation identification method were smaller than those of the Rugo’s liquid fixed sedimentation method,so the identification of the abundance of phytoplankton species by the membrane fixation identification method was reliable and stable.In general,the slope of the identification fit equation for the same gradient between the two methods is similar,and the correlation is significant(R2=0.958,P<0.01),and the Rugo’s fluid fixation sedimentation method has better fitting effect(R2 extraction = 0.959 < R2 precipitation = 0.992),but there is no obvious difference,and the membrane fixation identification method detects more phytoplankton cells,so the membrane fixation identification method is better.The amount of phytoplankton algal density loss at the genera level is affected by the concentration and particle size of the phytoplankton.(2)Phytoplankton in different eutrophication waters were detected by Lugo’s liquid fixation sedimentation method and membrane fixation identification method,respectively,and the quantity,species and diversity of phytoplankton were compared.Among them,Xiangxi River and Neisha Lake belong to medium nutrition;Quest Creek and Guo Zhenghu are light and moderately nutritious;South Lake and Temple Lake are moderately and severely nutritious.There was no significant difference in the detection results of the dominant species of phytoplankton between the two methods.At the gate level,the membrane fixation identification method showed advantages in the identification of golden algae gate and naked algae gate in Xiangxi River and Guo Zheng lake,and there was no obvious difference in the level of genus.The variation and size of the various indexes of the two methods are more consistent to reflect the water body.The number of phytoplankton is consistent with the change of sample points,and the results are more uniform in light and moderate eutrophicationic water bodies,and the correlation is the lowest in medium nutrient water bodies,while the loss of membrane fixation identification method is smaller,which reflects obvious advantages.The degree of environmental interference with the membrane fixation identification method is small,the method and equipment are simple,the cost performance is high,the timeliness is better in field monitoring,the efficiency is high,and the manpower and material resources are saved.(3)The phytoplankton community structure of the Xiangxi River was detected by the membrane fixation identification method under the succession law of the reservoir dispatch,and the variation of the water quality indicators of the Xiangxi River Reservoir bay in the three gorges reservoir and storage process was larger,of which the average values of total nitrogen,total phosphorus and conductivity in the discharge process were higher than those in the water storage process,and the average values of silica and water temperature were lower than those in the water storage process.There are 6 phytoplankton species in the storage and discharge process,mainly green algae phylum,followed by cyanobacteria phylum and diatom phylum.However,the water storage period is less than the drainage period of 8 genera,of which there are 10 genera less in the phylum of green algae.The diversity index and uniformity index of the water storage period are larger,the diversity is unstable,and the richness index is smaller.The cell density and species composition of phytoplankton Are greater than during the drainage period,and the algae density of the water storage period is decreasing with time,and the drainage period is constantly fluctuating.The water storage period is dominated by cyanobacteria,the diatom content is small,and the discharge period is dominated by green algae,and diatoms account for a relatively large proportion.The cell density of phytoplankton during the water storage period was mainly affected by water temperature(P<0.01),which was significantly positively correlated with chlorophyll a(P<0.01)and negatively correlated with total nitrogen,total phosphorus,nitrate nitrogen,and p H(P<0.01).Phytoplankton cell density was significantly positively correlated with dissolved oxygen,chlorophyll a,ammonia nitrogen,and p H(P<0.01),and was significantly negatively correlated with conductivity and silica(P<0.05).