Characteristics Of Planton Community Structure Between Maqu And Hukou In The Main Strem Of Yellow River

The research on the communities of plankton is significant for the fisheries industry and the basic theories of freshwater ecology.Currently,there are limited works on the structure of the plankton communities in the main stream of Yellow River,especially for the location between Maqu and Hukou section.In the paper,we present the structures of phytoplankton communities and zooplankton communities in Maqu section,we analyze the composition of the categories,the amount,dominant species and diversity of the plankton,which was sampled in these areas during April to May and July to August in 2006.The following are main results:1.1 Structure of the phytoplankton communities1.1.1 27 species(genera),5 phylum of phytoplankton were observed in the whole paragraph, among which there was Bacillariophyta 14 species(genera),Chlorophyta 5 species(genera), Cyanophyta 4 species(genera),Euglenophyta 2 species(genera),Cryptophyta and Pyrrophyta 1 species(genera).The variety of phytoplankton species in each station is inconspicuous,the dominate algae was Bacillariophyta,the next is Chlorophyta.The structures of phytoplankton communities showed no significant difference.1.1.2 The density range of phytoplankton was 3.2×10⁴ cells·L^-1～54.3×10⁴ cells·L^-1;the average density was 17.3×10⁴ cells·L^-1;the range of biomass was 0.061mg·L^-1～0.44mg·L^-1,the average biomass was 0.25mg·L^-1.There was no significant difference on the density and biomass of phytoplankton between spring and summer.1.1.3 The dominant species of phytoplankton was as the following:Gomphonema sp.,Synedra sp.,Navicula sp.,Nitzsschia closterium,Cymbella sp.,Closterium sp..1.1.4 Comprehensive index demonstrated that the water quality was polluted slightly in Maqu section.1.1.5 A negative correlation was present between the density and biomass for phytoplankton and altitude in spring and summer.Namely,the density and biomass of phytoplankton descended along the ascensus of altitude.2.1 Structure of the zooplankton communities2.1.1 18 species(genera),2 phylum of zooplankton were observed in the whole paragraph, among which there was Protozoa 13 species(genera),Rotifer 5 species(genera),with a ratio of 72.2%and 27.8%.Enerally,Protozoa was dominant specie in the river for spring and summer.2.1.2 The density range of zooplankton was 670cells·L^-1～1420 cells·L^-1;The average density was 936.27 cells·L^-1;the range of biomass was 0.044～0.98 mg·L^-1,the average biomass was 0.25 mg·L^-1.The density and biomass of zooplankton showed significant different between spring and summer.2.1.3 The dominant species of zooplankton was as the following:Amoeba,Diffusion.2.1.4 The zooplankton community composition in Yellow River from Maqu to Hukou was not stable and easily interfered by external environment.2.1.5 A negative correlation was also present between the density and biomass for zooplankton and altitude in spring and summer.Namely,the density and biomass of zooplankton dascend along the descent of altitudeIn a word,the investigate on the structure of the plankton communities between Maqu and Hukou section displayed that the simple composition and structure led to lower species diversity, and standing stock of phytoplankton presented negative correlation with altitude.Moreover,the water quality was polluted slightly via analysis on comprehensive index.The investigations were beneficial to further study the fundamental theory of system science of freshwater ecology for this river basin.