Study On The Change Structure Of Phytoplankton Community Near The Jiuduansha Wetland Nature Reserve Waters

Shagnhai Jiuduansha Wetland Nature Reserve is located between the south and north troughs of Sand Bars in the Yangtze River estuary, is the youngest sand bar by the coast in the Yangtze River. It generally keeping the state of native estuarine wetland, is the typical estuarine ecosystem, has great value for conserving and researching. The study is in February, May, September and November of2012and in February, August, September and November of2013. We set up thirteen sampling sites between Wusongkou and Lower Jiuduansha to make a comprehensive survey about species composition, the biomass and dominant species of its phytoplankton. The paper analyzes the community structure and varying pattern of phytoplankton in Jiuduansha, and to discuss the relationship between these rules and environmental factors. Then we study the laws of every population in these phytoplanktons, And annual variation of community structure of phytoplankton were studied. The main results are listed as follows:1. From2012to2013, there are147species of phytoplankton in the basin waters near at Jiuduansha shoals (including Varietas and Formas), which belong to87genera of8phyla. Bacillariophyta and Chlorophyta are the main phytoplankton. In these spices, most of them are Bacillariophyta, a total of44genera and76species, accounting for51.7%of the total of the species. Chlorophyta have28genera and44species, which account for29.9%of the total of the species. For the seasonal change of species, the number of spices in summer of2012is the most, but in winter of2012is the least; the number of spices in spring of2013is the most, but in autumn of2013is the least. The yearly average amount of phytoplankton was74.11×104ind/L in the seasonal investigation. Phytoplankton biomass has obvious change with seasons. More in spring, less in autumn of2012. But in2013, the number of species in autumn is the most, and the number of species in spring is the least. In the spring of2012and the fell of2013, the number of phytoplankton significantly is greater. There are5dominant species in the basin waters near at Jiuduansha shoals:Skeletonema costatum, Melosira granulata var. angustissima, Melosira granulate, Synedra acus and Cyclotella meneghiniana. Skeletonema costatum was the main dominant species in the basin waters near at Jiuduansha shoals. The change of its number determines the number of phytoplankton.2. From2012to2013, there are103species of phytop lankton in Huangpu River, which belong to69genera of8phyla. Bacillariophyta is the main phytoplankton, following is Chlorophyta and Cyanophyta. Bacillariophyta have35genera and43species, which account for41.7%of the total of the species. And Chlorophyta have28genera and44species, which account for%of th33e total of the species. The average biomass is19.56×104ind/L. More in winter, less in summer of2012. And in2013, the number of species in autumn is the most, the least in summer. The number of phytoplankton is well-distributed in Huangpu River. There are6dominant species in the surrounding waters:Melosira granulata, Melosira granulata var. angustissima, Cyclotella meneghiniana, Asterionella Formosa, Melosira varians and Chroomonas acuta. The dominant species in different seasons are different, but Melosira granulata, Melosira granulata var. angustissima and Cyclotella meneghiniana are the same dominant species in each season. The phytoplankton quantity of The Huangpu River is significantly less than the basin waters near at Jiuduansha shoals. The quantitative distribution of phytoplankton in the survey area (from Wusongkou to Lower Jiuduansha) was low-high-low pattern, but in Spring of2012and Autumn of2013, the number of phytoplankton showed a trend of increasing.3. Skeletonema costatum was the main dominant species in the investigated area (except the Huangpu River). It took over65%of the total quantity of phytoplankton in each sampling sites. From Wusongkou to Lower Jiuduansha, the quantity of Skeletonema costatum showed a trend of increasing. The amount of species was the most in spring in the year of2012and the the most in autumn in the year of2013. Skeletonema costatum become the main dominant species lower South Jiangyasha,and it took over70%of the total quantity of phytoplankton in each sampling sites. The reason why Skeletonema costatum grew plentifully and became the single dominant species was the complex environment in this area, the wild tolerance ability of Skeletonema costatum and the rich nutrient salt in the Maximum Turbidity Zone. 4. SPSS analysis of phytoplankton indicated that Salinity, TDS, turbidity, COD, TOC showed a very significant positive correlation with the biomass, have a very significant negative correlation between the biomass and SD; BOD have positive correlation with phytoplankton density, but TN have negative correlation with phytoplankton density. SPSS analysis of the number of Skeletonema costatum indicated that the major environmental factor which impact its density was Salinity, TDS, turbidity. Salinity, TDS and turbidity have a very significant positive correlation with its biomass; There is a very significant negative correlation between its biomass and TN; COD, TOC have positive correlation with its biomass.In conclusion, the species were abundant in and near the Jiuduansha Wetland Nature Reserve waters, Skeletonema costatum was the main dominant species in the investigated area. Tides, flows, water temperature and nutrient salt et al. affected the quantity distribution characters of phytoplankton through Skeletonema costatum. This research was one part of the entirety environmental information research of the Jiuduansha Wetland Nature Reserve, would provide a scientific basis for the research on the current characteristics and ecological restoration of community structure of phytoplankton.