Effects Of Embankment Project On Plankton Community In Chongming Dongtan Wetland

Chongming Dongtan Wetland is the largest and most well-developed estuary-type tidal wetland in the Yangtze River Estuary.It has abundant resources of plants,invertebrates,fish,amphibians,reptiles and birds.The particularity of the geographical location and the characteristics of the rapidly evolving ecosystem make Chongming Dongtan an important ecologically sensitive area of international significance.Chongming Dongtan Salt Marsh Wetland Embankment Project is an ecological restoration project for the purpose of removing invasive species.Through the construction of embankment,the invasive species Spartina alterniflora are removed to provide suitable habitat and and adequate food sources for birds.While the ecological restoration project is in progress,it will inevitably have an impact on the water body of Chongming Dongtan,blocking the exchange between water bodies.As an important group of wetland water bodies,plankton is not known to be affected by the embankment project,which seriously affects the ecological benefit evaluation of the embankment project.Therefore,this study raises a scientific question: How does the embankment project affect the species composition,community structure and seasonal changes of plankton in the Chongming Dongtan wetland?Focusing on the scientific issue of the impact of the embankment project on the plankton community in the Chongming Dongtan Wetland,this article first compares the differences in the plankton communities inside and outside the Chongming Dongtan Wetland embankment.On this basis,the differences of plankton communities in the microenvironment within the embankment were further explored.The research results will reveal the impact of the embankment project on the plankton community in Chongming Dongtan wetland,and provide a scientific basis for assessing the ecological risks of large-scale project construction.The results of the impact of the Chongming Dongtan embankment project on the plankton inside and outside the dike has showed that compared with the natural tidal creek outside the embankment,the embankment project reduced the species diversity and evenness index of the plankton in the embankment.The species,density,and biomass of zooplankton in the embankment has decreased,and the number of phytoplankton species has decreased,but the density and biomass of phytoplankton broke out.In addition,there are differences in the species composition of plankton inside and outside the embankment.The restoration area inside the embankment and the natural tidal creek outside the embankment had their own characteristic species.The main groups of plankton also showed different composition with the change of seasons,and different plankton community structures appeared inside and outside the embankment.The hatching level of dormant zooplankton eggs in the embankment was higher than that of the natural tidal creek outside the dike,which was very important for maintaining the number of zooplankton in the water body in the restoration area.The embankment project has increased the salinity of the water in the restoration area within the embankment,which also explains to a certain extent the reasons for the changes in the zooplankton community structure,while other physical and chemical factors of the water body had little difference between the inside and outside of the embankment,mainly affected by the season.On the whole,the impact of the dike project on the plankton in the dike was negative.The results of the Chongming Dongtan embankment project on the community variation of plankton in the microenvironment within the dike showed that the seasonal changes of plankton were obvious.The diversity and evenness index is higher in summer,and lower in winter.In summer,due to the mass reproduction of nauplius,the density of zooplankton was higher but the biomass level was lower,while the biomass and density of zooplankton were the highest in autumn.The number of species,density,and biomass of plankton in the embankment varied significantly between regions.In terms of spatial distribution,as the salinity increased from south to north,the density and biomass of plankton has decreased.The increase in water salinity caused by the dike project had a very obvious impact on zooplankton,and it was one of the important factors in the change of the zooplankton community structure in the embankment.The impact of the embankment project on phytoplankton did not show a uniform pattern with the zooplankton.The higher phytoplankton biomass in the restoration area was consistent with the chlorophyll level of the water body.The short-term cyanobacteria and dinoflagellate outbreaks in winter reduced the species diversity and uniformity index,and overall,there was eutrophication in the embankment.In general,the results of this study had showed that the Chongming Dongtan embankment project has changed the species composition and community structure of plankton in the embankment,regardless of the scope of the microhabitats inside and outside the embankment.The Chongming Dongtan embankment project changed the species composition and community structure of plankton in the embankment,and also had a greater impact on the main groups of plankton,making the natural tidal creek and the plankton community structure in the dike were different.The dike project reduced the diversity of plankton in the embankment,increased the biomass,and changed the physical and chemical factors of the water body.The embankment project blocked the exchange between the water body in the restoration area and the outside water body,which increased the salinity in the dike.This article provides basic data for the study of plankton in the Chongming Dongtan wetland.The impact of the embankment project on the plankton in the Chongming Dongtan requires a longer period of investigation,monitoring and research,strengthening the inter-annual changes and simultaneous observations of multiple groups.The period of this research is short,and it is impossible to analyze the impact of the embankment project on the plankton community in Chongming Dongtan wetland from the perspective of longer-term changes.In addition,the impact of the embankment project on the Chongming Dongtan wetland requires a comprehensive analysis of complex biological and non-biological factors.