Studies On Community Structure And Production Of Zoobenthos In Junshan Lake

Zoobenthos is an important components of lake ecosystem and play multiple functions in aquatic ecosystem. We studied zoobenthos of Junshan Lake from April 2005 to March 2006. Major contents of this paper were: the community structure of zoobenthos, species diversity and production of zoobenthos and so on. Thus zhoobenthos were rationally utilizated for fishery. The main results were given as follows:1,A total of 37 species were found in Junshan Lake,of which 10 species belong to 3 families in Lamellibranchia, 11 species belong to 7 families in Gastropoda, while 1 species belongs to 1 family in Polychaeta. 6 species of Oligoehaeta were found; 7 species of aquatic insects and two other animals were found.2,The average density and biomass of the zoobenthos in Junshan Lake were 197.72 ind./m² and 164.29g/m².The density and biomass of mollusca were 73.46ind./m² and 163.34g/m², respectively occupied 37.15% of total density and 99.42% of the total biomass. The density and biomass of Polychaeta were 90.65ind./m² and 0.35g/m², respectively occupied 45.85% and 0.21%. The density and biomass of Oligochaeta were 13.39ind./m² and 0.18g/m², respectively occupied 6.77%, 0.11%. The density and biomass of aquatic insect were 19.55ind./m² and 0.39g/m²,respectively occupied 9.89%, 0.24%.3,The Shannon-Wiener index, species evenness and richness index are calculated to assess water quality. The mean Shannon-Wienerin index was1.63, mean Margalef's index was 1.74,mean Simpson index was 3.59 and Pielou index was 0.63.The results of these index showed that the diversity was low.4,Based on the data from the density of zoobenthos communities, using the hierarchical clusterter of between-groups linkage method,10 stations are classed four groups: sand-soil group,soil group,float grass group and lotus root group. Using Non-metric Multi-dimensional Scaling method, the 10 zoobenthos communities were displayed in a 2-dimentional ordination configuration ,the results of which agreed with the results of cluster dendrogram. It is revealed that some environmental factors are closely interrelated with community of zoobenthos.5,Secondary production of major groups of zoobenthos in Junshan Lake was calculated. Production (in g.m^-2.yr^-1) and P/B ratios of zoobenthos in Junshan Lake:(1) Oligochaete (wet wt). B. sowerbyi, 0.6181,3.7 5.(2)Polychaeta(wet wt).Nephthys polybranchia,2.5322,7.64, (3) Chironomids (wet wt). Pentaneura sp.,0.1335, 6.39.(4) Mollusca. C.fluminea (AFDW), 1.036, 1.065. R.auriculata (wet wt), 3.5592, 0.27.