Characteristics of Community Structures of Phytoplankton in the Jiuduansha Wetland and its Adjacent Waters of the Yangtze River Estuary

The phytoplankton of ten sampling sites between Wusong Estuary and Lower Jiuduansha was investigated seasonally in spring,summer,autumn and winter in 2012.Community structure and their relationship with environmental factors were also discussed.139 species of phytoplankton belonging to 84 genera were found in this investigation.The species of diatom was the most and took 51%of all species.Green algae was the second,taking 31%of all species.The major phytoplankton species,according to their ecotype and habitat,can be grouped into freshwater,coastal and eurysalinity.The phytoplankton biomass in winter was the lowest and in spring was the highest.The average cell abundance of phytoplankton in winter was(12.6±1.2)×10~4 cell/L and was(117.3±6.5) X 104 cell/L in spring,respectively.The Skeletonema costatum was the single dominant species in all seasons and led to low diversity and uneven distribution.In addition,the environmental factors affecting the quantity distribution characters of phytoplankton differed in different seasons.Water temperature was the main limiting factor for phytoplankton growth in winter.Salinity greatly promoted phytoplankton growth in spring.The strong flows of wet season in summer led to rich nutrient advantageous to phytoplankton growth.