Ecology Of Zoobenthic Community In Jiuduansha Shoal

The study regards the new wetland on the Yangtze Estuary-Jiuduansha shoals, and investigate the zoobenthos through several times. The species composition, density and biomass were studied and the ecological characteristics were analyzed. Now carry on the discussion, explain the relation between zoobenthos and Jiuduansha wetland succession, also offer scientific basis for the protection and development of Jiuduansha.Major conclusions of the study were:1. Based on the data collected from four samplings on the spot on the macro-benthic invertebrate community in the Jiuduansha shoal from may,2002 to December,2004. A total of 31 species were identified. There are 24, 25, and 22 species of macrofauna in Shangsha, Zhongsha and Xiasha respectively. They can divided into three categories, i.e., fresh water species, brackish water species and sea water species, which reflects the ecological characteristics of zoobenthic community in estuarine ecotone. The zoobenthos of Jiuduansha shoals getting firm ability and sport ability poor species, demonstrate two kinds of different adaptation ways, one bury or live in caves life style, another have life style adhere to something.2. With the passage of time, there was continuous silt for the Jiudunasha shoal and expanding along longitudinal gradient of the estuary, and community succession taken place. There was clear space ecological pattern in zoobenthic diversity in the Jiuduangsha shoal, displaying differences in estuarine longitudinal gradients as well as in elevational gradients. Shangsha was earliest to form time and it development was faster than Zhongsha and Xiasha.But because erode more serious the number of zoobenthic species and biomass is smaller than Zhongsha. Xiasha was latest to form time, but the succession speed is fast. There was significant differentiation in community structure and diversity of zoobenthos from saline algae zone, Scirpus mariqueter zone to reed community zone along elevational gradient of tidal flat, which reflected the success process of zoobenthic community with the passage of time and the difference of its tolerance to environmental factors. These patterns closely related to its developing time, stability and complexity of habitats. Space ecologicalpattern of diversity also reflects the success of zoobenthic community of the new estuarine shoal in time.3. The complex topography and habitat heterogeneity resulted by Jiuduansha creek system is representative characteristic of mud flat wetland of estuary, which relate to distribution, structure and diversity of macrofaunal community closely and result in from bottom of creek, bank of creek to grass tidal flat, the change of zoobenthic species composition exhibits that from Natantia to Bivilvia and Polychaeta to Castropoda and Reptantia, the change of zoobenthic life form from swimming form to infaunal form to ahhering form and caving form. Density and biomass for macrobenthic communities of different habitats were in order of creek>grass tidal flat>bottom of creek, H and J for macrobenthic communities of different habitats were in order of grass tidal flat>creek> bottom of creek. The variztions in composition of species, types of life form and life group reflect ecological series of macrofauna adapting to creek habitat but also indicates the influence of gradient variation of environmental factors in creek system.4. On the Jiuduansha shoal, Phragmites culms and Sesarma dehaani burrows provided variations in surface topography and Phragmites rhizomes and roots add structural heterogeneity to the subsurface environment. The micro-topographical element has important effects on the zoobenthic community. The study showed that in the high marsh of the Jiuduansha shoals nematodes and copepods were numerically the most abundant meiofauna taxon. There were more total meiofauna in samples from the top than from the under.The meiofaunal density in samples taken between plants was higher than in samples from around plants, taken around crab burrows was higher than that in samples from between cra...