Abstract:

 As a key indication of aquatic ecosystems，phytoplankton is essential for the management of rivers health，and laws of the distribution of phytoplankton have attracted extensive attention Under the condition of urbanization，algae population characteristics and formation of laws in rivers were very complicated In recent years，niche research played an important role in exploring the biological community structure characteristics，population evolution and biodiversity In this study，niche was applied to study phytoplankton distributions in the ancient canal，an urban river connected with the Yangtze River in Zhenjiang In the spring （April 23），summer （August 20），autumn （October 10） and winter （December [JP3]17） of 2011，the composition and quantity of phytoplankton were investigated in 8 field sampling sites，and the modified [JP2]Levins and the Petrailis formulae were used to measure niche breadths and overlaps of the phytoplanktons [JP]dominant species The results showed that there were 11 dominant species of phytoplankton belonging to 4 phyla，including Dactylococcopsis， Microcystis，Aphanizomenon，Cyclotella，Melosira，Navicula，Chroomonas， Euglena，Crucigenia，Chlorella，and Scenedesmus，and dominant species were diverse in 4 seasons in this river Furthermore，niche breadths and overlaps of dominant species [JP2]differed in different periods Different dominant species had different adaptive capacity to the environmental [JP]factors In spring and autumn，Crucigenia and Microcystis had broadest niche respectively，and Chlorphyta，Cyanophyta were the main developing dominant species In summer and winter，Cyclotella had the broadest niche，and diatom was obviously dominant Being connected with the Yangtze River，habitat conditions in this river are affected by the operating of floodgate Some factors including the water temperature，the nutrient level and the suspended sediments in water are also under the effects Accordingly，phytoplanktons niche features were also affected Therefore，in this river，changes of the structure of phytoplankton community，and differences of niche among dominant species，both closely related to changes of river habitat conditions in different periods This study revealed the functional status and ecological adaptability relationship of dominant species of phytoplankton in this river Relevant results are expected to provide some references for obtaining phytoplankton distribution characteristics in similar rivers