Study On The Community Structure Of Phytoplankton And Environmental Impact Assessment In Harbin Section Of Songhua River

In spring, summer and autumn of 2008, the water samples were collected from 7 monitoring sections which were set in the research of Harbin section of Songhua River. The qualitative and quantitative analysis of phytoplankton was made, and the data we got was used to analyze the populations, community structure and biodiversity of phytoplankton in this water. And explore the correlation between phytoplankton and environmental factors in the way of gray relational analysis. Compared to methods of biological and non-biological assessment, a comprehensive evaluation on water quality of Harbin section of Songhua River was made, providing scientific and practical values with environment protection and pollution control of Harbin section of Songhua River.The phytoplankton of 7 sampling sites and three seasons in Harbin section of Songhua River were identified belonging to 98 species 51 Genera 7 Phylums, and the community structure mainly contained Chlorophyta, Bacillariophyta and Cyanophyta, while the most is green algae included 41 species,32 species of diatoms followed, green algae was 19 species and the rest were 6 species. The average of abundance and biomass of phytoplankton were 211.36×105 ind./L and 27.63mg/L in three seasons in Harbin section of Songhua River, and the seasonal variations both were:autumn> spring> summer, while the horizontal distribution both were 3# highest and 1# lowest.The rangeability of Shannon-Wiener index was 3.13-4.23bit in spring, summer and autumn in Harbin section of Songhua River, while Pielou evenness index ranged from 0.51-0.69 and Margalef index ranged from 4.50-5.01. The seasonal trend of Shannon-Wiener index was summer>spring>autumn, so was Pielou evenness index, and the Margalef index was summer>autumn>spring. There was significantly positively correlated between Pielou evenness index and Shannon-Wiener index, meanwhile, Margalef index and the abundance was negatively related. All the indexes can express the diversity of phytoplankton of Harbin section of Songhua River well.Pearson correlation analysis suggested:there was no significant correlations between environmental factors and the abundance in spring and autumn, either between environmental factors and biomass in three seasons (p>0.05). In summer, the abundance and TN was positively correlated, espicially with TP, BOD5, NH3-N, COD and permanganate index were all significantly positively correlated (p<0.05, p<0.01), however, the abundance and water temperature was a significant negative correlation(p<0.05), which doesn't match the fact.Grey relational analysis showed:the most strongly influence factors of phytoplankton were water temperature and nutrients in different seasons and sampling sites of Harbin section of Songhua River, in fact, human disturbance was the main factor.The results of combining a variety of evaluation methods, a general conclusion was drawn:Harbin section of Songhua River was eutrophication, and the order of horizontal distribution of water quality from good to bad was:1#>7#>4#>6#>2#>5#>3#.The construction of Dadingzishan Navigation and Hydropower Project leaded to raising the water level to meet the environmental flows of this water, and the reduction of flow rate can undermine the self-purification capacity of this river. The combined effects of many factors resulted the slow succession of phytoplankton community structure from blue and green algae to the diatom. When the situation of water temperature, nutrients and flow rate all possess in summer, the algal bloom may break out.