Temporal And Spatial Variations In Phytoplankton Community And Their Correlations With Environmental Factors In Shengjin Lake

In the present study, we examined species composition, the dominant species, density and the temporal and spatial distribution of the phytoplankton community to understand the phytoplankton community structure characteristics from February to July 2014 in the upper lake of Shengjin Lake. Pearson correlations and Redundancy analysis (RDA) method were used to analyze the main environmental factors affecting phytoplankton community structure.1. Marked temporal and spatial variations were observed in the main environmental factors of the upper part of Shengjin Lake, and the water quality situation in different sample sites was different. The water quality conditions in 1-3 and 1～13 sample sites were relatively poor. The reason of poorer water quality conditions in 1～3 sample sites were was that the sites neighboring village were contaminated by human interference. And the poorer water quality conditions in 11～ 13 sample sites is because that the sites near the wintering waterbirds gathering place where nutrients were rich.2. Phytoplankton community was mainly composed of Chlorophyta and Bacillariophyta in the upper lake of Shengjin lake. A total of 192 species of phytoplankton belonging to 8 phyla and 84 genera were identified. Chlorophyta accounted for 46.4% of total number algae species, which had 89 species belonging to 37 genera. Bacillariophyta accounted for 29.2% of total number algae species, which had 56 species belonging to 24 genera. Cyanophyta accounted for12.5% of total number algae species, which had 56 species belonging to 24 genera. The 14 predominant species belonged 5 phyla. Marked temporal and spatial variations were observed in the phytoplankton community. The dominant species underwent substantial changes from Bacillariophyta and Cryptophyta to Cyanophyta and Chlorophyta. The total abundance of phytoplankton ranged from 3.66 ×105 cells/L to 867.93 ×105 cells/L, with the total biomass of phytoplankton ranging from 0.40 mg/L to 20.89 mg/L. The phytoplankton biomass and abundance showed a similar increasing trend from February to July. The abundance gradient rose from February to Jun e and fell from June to July, but the biomass gradient rose all the way. The Shannon Wiener diversity index varied from 3.50 to 8.35 with an average of 5.58; Pielou evenness index varied from 0.14 to 0.83 with an average of 0.60; Margalef index varied from 0.87 to 9.99 with an average of 3.82. The diversity indices of phytoplankton community in Shengjin Lake revealed obviously temporal and spatial variations.3. The most significant environmental factors influencing phytoplankton community were water temperature (T), transparency (SD), and nutrient concentration, with other environmental factors such as pH, DO, COD, SS, NO2-N, turbidity, conductivity, and crustacean zooplankton, also important. Pearson correlations revealed that:total phytoplankton abundance showed a significant positive correlation with T, pH, crustacean zooplankton, SD and COD (P< 0.01); but a negative one with DO, turbidity, SS and NO2-N (P< 0.01). Also, the total algal biomass presented a positive relationship with T, pH, SD and crustacean zooplankton (P< 0.01); but a negative one with SS, DO, conductivity and COD (P< 0.05). Redundancy analysis showed that phytoplankton responded well to SD, T, Cond, NO3-N, and TP throughout the sampling period in the upper lake. During the study, most dominant species clustered along the variables of SD, NO3-N, and TP.4. Through the analysis of the water quality situation and the temporal and spatial characteristics of phytoplankton density, biomass and diversity index in the upper lake of Shengjin lake, the influence from the droppings of wintering waterbirds on phytoplankton community structure was deduced. The result shows:the droppings of wintering waterbirds improved the nutrient content of nearby waters, which promoted the growth of phytoplankton and then formed the high value area of phytoplankton biomass. But with the consuming of nutrients and the significant changing of other environmental factors, high value area moved. All of these formed the characteristics of spatial and temporal heterogeneity of phytoplankton community structure in the upper lake of Shengjin lake.