Phytoplankton Community Structure And Analysis Of Correlations With Environmental Factors In Sand Lake In Ningxia

Sand Lake is a typical sub-humid land northwest of semi-desert lake. In recent years, due to human intervention and interference, water quality changes quickly. Therefore Sand Lake effective monitoring and health evaluation not only necessary but urgent. Phytoplankton is an important index for water quality, by analyzing the composition of phytoplankton community structure can be analyzed and evaluated where the water, This has important implications for the protection of Sand Lake.The research established 8 typical sampling stations according to uniform distribution, and samplings were done from Spring(April)、Summer(July) and autumn(September).Qualitative and quantitative investigations were conducted to the phytoplankton of samplings, and simultaneously the corresponding water environmental factors were monitored and analyzed. Multivariate statistical method was used to analyze phytoplankton’s biodiversity and the community structure. The correlation between phytoplankton and environmental factors was determined by CCA analysis. The research could provide scientific basis for the protection and management of Sand Lake.Between April to September, by Sand Lake investigation, a total of 7 phyla,56 species were identified, including Chlorophyta, Bacillariophyta, Cyanophyta, Pyrrophyta, Chrysophyta, Cryptophyta and Euglenophyta.Among which, the majority were chlorophyta(23 species), bacillariophyta (14 species), cyanophyta(10 species), chrysophyta(5 species), euglenophyta(2 species), pyrrophyta and cryptophyta each have only one specie. Temporal distribution of species richness of phytoplankton was obvious, the most (39 species) occured in April, and the next (38 species) occured in July, the least (30 species) occured in September. On the spatial distribution, species richness was the most (39 species) at 2#, and the least (30 species) at 4#. A total of 32 dominant species was found. The number of dominant phytoplankton species was the least in September, while its dominant degree was high. The number of dominant species was the most in July, and its dominant degree was low. The major phytoplankton compositions were Chlorophyta, Bacillariophyta and Cyanophyta throughout the year.The temporal and spatial non-uniformity of phytoplankton’s abundance and biomass were remarkable in Sand Lake. Changes in the scope of abundance between 0.70×104 to 41.46×104ind./L; Changes in the scope of biomass between 0.21 to 14.31 mg/L.On the temporal distribution, the highest abundance and biomass were in July, the lowest were in April. On the spatial distribution, the highest abundance was in 2# and the lowest was in 6#,the highest biomass was in 1# and the lowest was in 4#.The water environment had significantly different between 1#,2# and 4#,6#.Temporal and spatial distributions of phytoplankton’s biodiversity indexes were remarkable in Sand Lake. The Shannon-Wiener index was 2.57-3.94, the Margalef index was 1.37-3.38,and Pielou index was 0.32-1.22 during the whole year. The Shannon-Wiener index and Margalef index were highest in April, and the lowest in September; the Pielou index was highest in September, and it was the lowest in July. The diversity index in the undisturbed areas was significantly higher than the areas which were affected by human activities in Sand Lake.After canonical correspondence analysis (CCA) display, that water temperature and turbidity were main factors affecting the distribution of phytoplankton community, biochemical oxygen demand and total nitrogen were also significantly positively correlated with the phytoplankton species distribution.