Study On The Community Ecology Of Zooplankton In Tidal Creeks Of The Chongming Dongtan Intertidal Flat

Tidal creeks, the important geomorphology of East Mud Flat of Chongming Island and an important component of Changjiang estuarine ecosystem, are the vital Link between adjacent aquatic ecosystem and Chongming Dongtan wetland ecosystem. Zooplankton is regarded as one of the key secondary producers. Its dynamic changes have important regulating effect on structure and function of the whole ecosystem, fishery resources and environment, and reflect the health status of ecosystem directly. The research on zooplankton in tidal creeks of the Chongming Dongtan intertidal flat help us to make a comprehensive knowledge of structure and function of Chongming Dongtan wetland ecosystem, and to provide basic data and theoretical basis for maintaining diversity of East Mud Flat of Chongming Island.According to the distribution of tidal creeks,18 stations in six tidal creeks (S1-S6) were selected for sampling during four seasons from April 2008 to December 2009. The seasonal and tidal variation of species composition, dominant species, community structure, species diversity, and quantitative distribution were recorded in this study. The results also provided valuable data for the research on biological resources in tidal creeks of the Chongming Dongtan intertidal flat. Meanwhile, through comparing the results of ecological characteristics of zooplankton in the tidal creek (S7) before and after reclamation, this thesis proved the influence of diking on community structure and diversity and the succession of community after reclamation. The findings also provide some advices for diking in the future. The results and conclusions were listed as following:1. Species composition and diversity of zooplankton in tidal creeks of the Chongming Dongtan intertidal flatA total of 47 species and 9 groups of pelagic larva, belonging to 6 taxa, were identified. Among them, Copepoda were dominant, accounting for 78.7% of the total recorded species. There were 38 common species between 2008 and 2009.6 kinds of copepods, such as Tortanus vermiculus, Thermocyclops taihokuensis, Cyclops vicinus lobosus et al, were not found in 2009, while Sinocalanus dorrii, Labidocera euchacta Giesbrecht, and Diaphanosoma aspinosum were not found in 2008. There were ten dominant species which were Sinocalanus sinensis, Sinocalanus tenellus, Schmackeria poplesia, Halicyclops sinensis, Halicyclops latus, Limnoithona etraspina, Nitocra lacustris, Tachidius triangularis, Mesochra quadrispinosa, and Microsetella norvegica. Sinocalanus tenellus was the most dominant species in spring, Schmackeria poplesia in summer, Schmackeria poplesia and Sinocalanus sinensis in autumn, and Limnoithona etraspina, Sinocalanus sinensis (2008) and Mesochra quadrispinosa (2009) in winter.Shannon-Wiener indices (H') peaked in summer, species richness indices (d) were higher in summer and autumn, and Pielou evenness indices (J') were higher in winter and spring (2009). Compared with data from North Channel and the North Branch of the Yangtze River Estuary, only eight common species were found, demonstrating significantly different species composition. The ecological characteristics of zooplankton were also related to tide; species diversity, dominant species and the dominance were different during flood and ebb tide. Environmental factors, such as salinity, temperature, runoff, and tidal current influenced the temporal and spatial distributions of zooplankton in tidal creeks.2. Quantitative analysis of distribution and variations of zooplankton in tidal creeks of the Chongming Dongtan intertidal flatQuantitative distribution and seasonal variations of zooplankton in the tidal creeks of the Chongming Dongtan intertidal flat were studied based on seasonal investigation data obtained from April 2008 to December 2009. The result showed that the total abundance of zooplankton was high in all seasons between over 2.21×103 ind/m3 in winter and over 10.00×103 ind/m3 in other seasons. The total abundance of zooplankton changed obviously with seasons, and the variation trend was:spring>autumn>summer > winter. Due to tide effect, the abundance in flood tide was higher than that in ebb tide in summer, autumn and winter, but in spring.The horizontal distribution of zooplankton was different in six tidal creeks and among 7 main dominant species. The result also showed that the total abundance distribution was determined by Sinocalanus tenellus, Sinocalanus sinensis, and Mesochra quadrispinosa in spring, by Sinocalanus sinensis and Schmackeria poplesia in summer and autumn, and by Sinocalanus sinensis, Schmackeria poplesia and Limnoithona etraspina in winter. In flood tide, the variation in total abundance was somehow related to temperature in spring and winter, but to salinity in summer and autumn.In flood tide, the variation in total abundance was somehow related to salinity in spring and winter, but to temperature in summer 2008 and autumn. In ebb tide, temperature and salinity were correlative to the total abundance in summer and winter 2008, and in spring, summer, and autumn 2009. Therefore, environmental factors, such as runoff and tidal current, also influenced the temporal and spatial distribution of zooplankton abundance in the tidal creeks. The abundance of zooplankton was positively correlated with the biomass according to Pearson correlation analysis, which showed that the horizontal distribution of biomass was similar to the abundance in the six tidal creeks.3. Influence of diking on community structure and diversity of zooplankton in tidal creek (S7) of the Chongming Dongtan intertidal flatOur results showed that 31 species in total were identified. The zooplankton community was composed of 25 species copepod,3 species of amphipoda,1 species of mysidacea,1 species of cumacea,1 species of isopoda, and 9 groups of pelagic larva. More species were observed before reclamation than after reclamation, while dominant species and community structure of zooplankton were relatively stable after reclamation. After reclamation, the abundance of zooplankton decreased obviously, while the biomass increased evidently on the contrary because of Neomysis japonica. Results of Shannon-Wiener indices, Pielou evenness indices, and simplicity indices showed that the species diversity was higher after reclamation than before reclamation, whenas species richness indices decreased slightly after reclamation.