| Xixi Wetland is an important urban wetland, and has a unique ecological service functions to Hangzhou city. As speeding up the urbanization process. Xixi Wetland has been damaged seriously. In recent years the quality of the water of Xixi had been improved obviously by the ecological protection engineering, but few attempts were paid to know whether interspecies relationships and the ecological process has been improved in Xixi. As the key groups of litter decomposition and nutrient cycling in wetland ecosystem, macrozoobenthos was the sensitive indicator in the health of the wetland ecosystem. In order to assess the present situation of macrozoobenthos in Xixi Wetland and the response to wetland ecological protection engineering, we studied the macrobenthos in species and functional group lever, and analyzed the impact on macrozoobenthos by environmental factors in Xixi Wetland.1. We recorded45species from15families,8classes and3phyla, most of them were Annelida, Mollusca and Chironomidae. Limnodrilus hoffmeisteri, Aulodrilus pluriseta and Bellamya purificata were the dominant species in Xixi Wetland. The density of Annelida of area Ⅰ, which was carried out early, was lower than area Hand area Ⅲ. However, the changes of density and biomass of Mollusca were different. Total density of macrobenthos in area Ⅰ had no significant differences between area Ⅱ and area Ⅲ. But there were significant differences in the total biomass, number of species, Margalef abundance index and Shannon-Weaver index. These results suggested that the diversity of macrobenthos had been increased and the quality of environment had been improved by the restoration project in Xixi Wetland. ANOSIM showed that the structure of macrozoobenthic communities differed significantly between different areas and seasons, and the main contributing species were A. pluriseta and B. purificata. It indicated that the two dominant species were sensitive to the chang of environment in Xixi Wetland which could be indicator species in environmental assessment of Wetland.2. The gathering-collectors were the dominant groups in Xixi Wetland, which the relative abundance was82%, and the relative abundance of the predators and the filter-collectors were very small. By the comparison of the later construction of area II and area Ⅲ, the relative abundance of gathering-collectors were significantly fall and the scrapers increased in the earlier construction of area Ⅰ. Margalef species richness indices, Shannon-Wiener diversity indices and Simpson indices of the gathering-collectors and scrapers in area Ⅰ was significantly higher than area Ⅱ and area Ⅲ. The analysis based on the function of ecological characteristics of wetland showed that the ability of the characteristic value of material circulation which was F1, F2and F3in area Ⅰ was significantly higher than area land area Ⅲ. The habitat stability represented by F8in area Ⅰ was significantly higher than area Ⅱ and area Ⅲ. It indicated that the long-term continuous protection in Xixi Wetland had changed the macrobenthic functional group structure greatly and increased the material circulation and habitat stability of aquatic ecosystem obviously.3. Analysis of the relationship between macrobenthos and environmental factors showed that zoobenthos biomass and the total phosphorus of sediment had a positive correlation relationship, while water depth and zoobenthic density including number of species, Margalef species richness indices and Shannon-Wiener diversity indices had a negative correlation relationship. The density of macrobenthos and six kinds of environmental factors had no significant relationship. Using BIO-ENV (biota and environment analysis), we found that water temperature was the key factor affecting the macrozoobenthic communities in spring and summer, whereas water depth was the key factor affecting the macrozoobenthos in autumn and winter. The total phosphorus of sediment was closely related to the macrozoobenthic biomass and community structure. |
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