Correlation Between Phytoplankton Community Structure And Environmental Factors Of Four Reservoirs In Bishan District Of Chongqing,China

The per capita water resource of Bishan district is 559 cubic meters,only a quarter of the country.Reservoir,an important water resource reserve project,has become the primary source of water supply in Bishan district.However,the existing data have indicated that the reservoirs in Bishan district are subject to varying degrees of pollution,and thus the water quality monitoring and management of these reservoirs are urgently required.In the present study,four representative reservoirs covering many types of reservoirs were selected from Bishan district,and their phytoplankton community structure and environmental factors were analyzed,which can reflect the health status of reservoirs in Bishan comprehensively.The results are as follows:1.In four reservoirs,there were 413 species(including variants)of phytoplankton,including 191 species of Chlorophyta,109 species of Bacillariophyta,62 species of Cyanophyta,24 species of Euglenophyta,12 species of Pyrrophyta,7species of Chrysophyta,6 species of Cryptophyta,and 2 species of Xanthophyta.All8 categories of phytoplankton were found in the Tongxin reservoir,but no species belong to Chrysophyta were found in the Shuangyu reservoir and no alga belong to Xanthophyta were found in the Kejiaqiao reservoir and Yanjinghe reservoir during the year;2.The dominant species in the whole year of the four reservoirs was Cyanophyta,in which Pseudoanabaena,Microcystis and Oscillatoria were the common species.Additionally,Botryococcus braunii in August,Aphanizomenon flosaquae in March,Cyclotella sp.and Chlorella sp.in March were the higher degree of dominance in Yanjinghe reservoir,Yanjinghe reservoir,Kejiaqiao reservoir and Tongxin reservoir,respectively;3.Shuangyu reservoir was mainly used for aquaculture which had the highest eutrophication among the four reservoirs.In August,it reached severe eutrophication level,and was also at moderate levels in other months.Kejiaqiao reservoir wasmoderately eutrophic throughout the year.Both Tongxin reservoir and Yanjinghe reservoir were drinking water sources,with relatively low in eutrophication.Tongxin reservoir reached moderate levels of eutrophication in August and March,while reached mild eutrophication in December and June.Yanjinghe reservoir was at a moderate eutrophication level in August and December,and reached mild eutrophication in March and June because of sediments and nutrient salts were dissolved in water;4.The correlation analysis and RDA analysis of four reservoirs showed that the growth and reproduction of phytoplankton in the Shuangyu reservoir and kejiaqiao reservoir were not limited by N and P.However,Yanjinghe reservoir was likely to be a P limited type reservoir,while phytoplankton in the Tongxin reservoir was affected by a variety of environmental factors;5.The four reservoirs were affected by cyanobacteria bloom in varying degrees.Because both Tongxin reservoir and Yanjinghe reservoir bear the function of urban and rural water supply,it is necessary to monitor constantly and prevent water polluted by the release of toxins from cyanobacteria bloom.