| Based on seasonal investigation on macrozoobenthos in Sihe River from July 2013 to April 2014, spatio-temporal variations of macrozoobenthic number of species, standing crop and dominant species were analyzied, and the water quality of Sihe River were evaluated using a variety of biological index, such as Shannon-Weaver index and Margalef index; the relationship between characteristics of macrozoobenthic community and environmental factors were also discussed. The result will provide biological evidence to improve the eco-environment of Sihe River. The main results were as following:1. A total number of 98 species were identified during investigation, of which, 12 species were annelid, 18 species were molluscs, 66 species were arthropods, and others were 2 species.The number of species in downstream was the lowest among six areas, while the number of species in tributary of midstream was highest. In four seasons, the number of species in summer was lowest with 36 species only, while highest numbers of species were occurred in winter and spring with 58 species respectively.2. The mean density and biomass of macrozoobenthos in Sihe River were 1787 ind./m2 and172.20 g/m2 respectively. The density of macrozoobenthos in summer was lowest, while which in spring was highest. The biomass was the highest in autumn but lowest in winter. The standing crop of annelid and molluscs in downstream tributaries were the highest, while in tributaries of upstream, the standing crop of arthropods were the highest. The highest standing crop of other animals were in upstream. The standing crop of annelid were most highest in spring, the density and biomass were 1529 ind/m2 and 3.70 g/m2 respectively. The standing crop of molluscs were the highest in autum, the density and biomass were 338 ind./m2 and 315.37 g/m2 respectively.The standing crop of arthropods were highest in winter and the lowest in summer. The mean density of other animals were highest in autum, but the mean biomass were highest in winter.3. The dominant macrozoobenthos of Sihe River were determined by the index of relative importance(IRI) and dominance index(Y). Bellamya sp., Limnodrilus hoffmeisteri and Corbicula fluminea were dominant species in Sihe River determined by IRI, while Limnodrilus hoffmeisteri, Branchiura sowerbyi and Glyptotendipes sp. were determined by Y. Species composition of dominant species are different between seasons. Dominant species were mainly composed of molluscs based on IRI. But oligochaeta and chironomidae were often become dominant species determined by Y, because abundance of those taxa were very high in Sihe River.4. Based on the Jaccard index, the species composition of macrozoobenthos varied significantly in different seasons, which indicate that habitats in areas are heterogeneous. The macrozoobenthos communities showed moderately similar between upstream and midstream but moderately dissimilar among other areas. The species of macrozoobenthos varied significantly in different areas as well. There showed medium similar between autum and winter, but moderately dissimilar among other seasons.5. Based on the analysis of ABC curves, it can be shown that the community of macrozoobenthos in Sihe River were steady as a whole, and has not been disturbed by environmental pollution. But there have showed the impact of disturbance on community of macrozoobenthos in summer.6. Water quality was assessed using Shannon-Weaver index, Margalef index, BI index and FBI index. It showed that the water of Sihe River on the whole was moderately polluted. The water quality was relatively worse in summer, while better in autum and winter.7. Based on analysis of Pearson correlation and CCA, the mainly environment factors that influenced the macrozoobenthic community and distribution are temperature, dissolved oxygen,nitrogen, phosphorus and chlorophyll. Chlorophyll mainly affected the distribution of macrozoobenthos. |
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