Community Structure of the Phytoplankton and Its Relationship with Environmental Factors in Lower Reaches of the Yellow River

[Objective] The research aimed to study community structure of the phytoplankton and its relationship with environmental factors in lower reaches of the Yellow River.[Method] From April to June in 2011,phytoplankton was conducted qualitative and quantitative researches in Lijin in lower reaches of the Yellow River.By combining population characteristics of the phytoplankton,its relationship with environmental factors was discussed.[Result] 114 species and 5 phylum of phytoplankton were observed in the whole river section.The abundance of the phytoplankton was 0.90×104-303.35×104 ind/m3,and mean was 27.20×104 ind/m3.The biomass of the phytoplankton was 0.008-5.890 mg/m3,and mean was 0.641 mg/m3.Shannon-Weaver diversity index,Pielou evenness index and Simpson's diversity index were respectively 1.59,0.36 and 0.55.SPSS data analysis indicated that transparency was uppermost environment factor affected the phytoplankton abundance.Phytoplankton abundance had positive correlation with transparency,and the regression equation was y=-393.8+115.5x-11.1x2+0.35x3(n=18,R2=0.952,F=92.665,P0.01).[Conclusion] The community structure of phytoplankton was unstable,and transparency was the uppermost environmental factor affected phytoplankton abundance in the lower reaches of Yellow River.