Relationship Between Algae Community Structure And Environmental Factors In The Lower Reaches Of Songhua River

In this study,five sampling sites were seted up in the lower reaches of Songhua River,namely Tangyuan,Jiamusi,Huachuan,Fujin and Tongjiang.Samples from the study area were collected in early June 2020 and late September 2020,respectively,and the physical and chemical factors of the water body were determined.The community composition of phytoplankton and parasitic algae was detected,and the aquatic biodiversity and the correlation between phytoplankton and parasitic algae and environmental factors were analyzed.The purpose of this study is to explore the response relationship between phytoplankton,algae and environmental factors in the lower reaches of Songhua River,so as to provide scientific basis for the detection,evaluation and restoration of aquatic ecosystem in the lower reaches of Songhua River.To provide a theoretical basis for aquatic ecological protection and pollution restoration and management in the lower reaches of Songhua River.The experimental results are as follows:(1)Environmental factors:the content of Chl-a is in the range of 2?g/L-5?g/L,the content of TP is in the range of 0.10 mg/L-0.31 mg/L,the content of COD_Mn is in the range of 4.10 mg/L-6.61mg/L,the content of salinity is in the range of 4.10 mg/L-6.61 mg/L,the content of TN is in the range of 4.10 mg/L-6.61 mg/L,and the content of EC is in the range of 201?s/cm-301?s/cm.On the time scale,the lower reaches of Songhua River has higher COD_Mn and TN,lower salinity and EC in summer,higher salinity and EC,lower COD_Mn and TN in autumn.On the spatial scale,Fujin has higher salinity and EC and lower Chl-a,while Tongjiang has higher Chl-a and COD_Mn and lower TP.There was no significant difference in TN among different sampling sites at the same time,but there was a great difference in different time.Pearson correlation analysis showed that salinity had a significant negative correlation with TN,a significant positive correlation with EC,and a significant negative correlation between TN and EC.(2)Phytoplankton:totally 6 phyla and 93 species of phytoplankton were identified,among which diatom was the most,followed by Chlorophyta and Cyanophyta.In summer,the average number of phytoplankton in the lower reaches of Songhua River was 107.86×10⁴ ind/L,higher than 20.00×10⁴ ind/L in autumn?The average biomass of phytoplankton in the lower reaches of Songhua River in summer was 0.9482 mg/L,higher than that in autumn(0.3038 mg/L).From the perspective of diversity index,Shannon Wiener diversity index H value fluctuated from 1.36 to 2.86,which was in the middle pollution;The Pielou evenness index J value fluctuated from 0.48 to 0.82,which was in the light or no pollution state;The D value of Margalef's species richness fluctuated from 1.33 to 2.51,which was in the middle?-Pollution in the environment.Comprehensive analysis shows that the lower reaches of Songhua River are in light or medium pollution state.(3)Epiphytic algae:6 phyla and 63 species of epiphytic algae were identified,among which diatom phyla was the most.In summer,the average number of epiphytic algae in the lower reaches of Songhua River is 0.1245×10⁴ ind/L,lower than 0.3972×10⁴ ind/L in autumn.The average biomass of epiphytic algae in the lower reaches of Songhua River was 0.3378 mg/L in summer,which was higher than 0.0044 mg/L in autumn.From the perspective of diversity index,the H value of Shannon Wiener diversity index fluctuated from 0.68 to 2.56,and all sampling sites were in medium pollution except Tongjiang;Pielou evenness index J value fluctuated from 0.23 to 0.97,most of the sampling sites were in light pollution-free,Margalef species richness D value fluctuated from 1.08 to 2.95,which was in low pollution?-Pollution in the environment.Comprehensive analysis shows that the lower reaches of Songhua River are in light or medium pollution state.(4)Correlation analysis between phytoplankton,phytoplankton and environmental factors Pearson:there was a significant negative correlation between phytoplankton biomass and salinity,and a significant positive correlation between phytoplankton biomass and Chl-a,TP.Redundancy analysis(RDA)showed that the environmental factors affecting phytoplankton biomass in the lower reaches of Songhua River were TP,Chl-a,COD_Mn,EC,Chl-an and salinity.The main environmental factors affecting phytoplankton biomass in the lower reaches of Songhua River were TP,Chl-a,COD_Mn,EC,Chl-a and salinity,and the main environmental factors were TN,TP and COD_Mn.To sum up,through the comprehensive analysis of phytoplankton and algae in the lower reaches of the Songhua River,the results show that the lower reaches of the Songhua River is in a state of light or medium pollution.Total nitrogen,total phosphorus and electrical conductivity are the main environmental factors affecting phytoplankton in the lower reaches of Songhua River,and total nitrogen,total phosphorus and permanganate index are the main environmental factors affecting algae.Both phytoplankton and algae can be used as good indicators for water quality monitoring in the lower reaches of Songhua River.