Community Structure Of Bait Organism In The Weidoushan Reservoir And Its Relationship With Environmental Factors

The Weidoushan Reservoir is a multi-functional reservoir located in Hongan county of Hubei province, which undertakes flood control, drought resistance and aquaculture functions and even is the alternate source of drinking water for the citizens of Hongan county. In recent years, aquaculture in the reservoir is more restrictive to protect its water environment. The reservoir mainly adopts an extensive cultivation mode which is with fingerling stocking and without artificial feeding and fertilizing, so the fishes rely mostly on the natural bait resource of the reservoir. Therefore, it is significant for the whole reservoir ecosystem to carry out bait biological research. We investigated the spatial and temporal variations of physical and chemical factors, community structure characteristics of bait organism in the reservoir, and the correlation analysis and RDA was used to study the interrelationship between bait organism and physical and chemical factors, and water quality of the reservoir was evaluated by the physico-chemical indicators and biological methods. The results are as follows:(1) The values of water temperature of the Weidoushan Reservoir fluctuated in the range of 12.8 ℃ to 28.1 ℃ all around the year. The dissolved oxygen level were relatively high, with the lowest mean value of 7.67 mg/L. Seasonal variation of COD ranged from 0.7348 to 1.7789 mg/L. P was the primary limiting factor of the reservoir.The content of NO2--N was relatively low, and it was difficult to detect its concentration in summer. The dynamics of pH and NO3--N values were relatively steady with the mean value of 7.70 and 0.1195 mg/L, respectively. The seasonal differences of the rest physico-chemical parameters were distinct. The value of comprehensive nutrition state index(TLI) in the Weidoushan Reservoir had a seasonal range of 26.9071~32.8605,which showed oligotrophic in winter and spring, and mesotrophic in summer and autumn.(2) A total of 184 species, 83 genera, eight phyla of phytoplankton were detected during the investigation, which were dominated by Chlorophyta, followed by Bacillariophyta and Cyanophyta. Totally 20 dominant species were identified, and most of them were indicator species of pollution. The average density and biomass ofphytoplankton were 18.82×105 ind/ L and 1.6910 mg/L, and both had striking seasonal differences. The Shannon-Wiener(H’) and Simpson(D) diversity indices, Margalef abundance index(Dm) and the Pielou evenness index(J) of phytoplankton were 2.38,0.80, 2.42 and 2.38, respectively. According to the results of correlation analysis and RDA, the community structure of phytoplankton in the Weidonshan Reservoir was mainly influenced by PO43--P and DO.(3) During the study, a total of 61 species, 45 genera of zooplankton were identified.Protozoa and rotifers dominated the zooplankton accounting for 47.54% and 39.34% of the total species respectively. Strobilidium velox, Strombidium viride, Urotricha furcata and Nauplius were in dominant all around the year. The average density and biomass of zooplankton were 12123.0 ind/L and 1.8763 mg/L, respectively. Margalef abundance index(Dm) of zooplankton was quite different in four seasons, and Simpson diversity index(D) and Pielou evenness index(J) showed uniform distribution both among seasons and sampling sites. Analysis of correlation and RDA revealed that PO43--P, Chl-a, DO and NH4+-N were the principal environmental factors to influence the community structure of zooplankton in the Weidonshan Reservoir. Moreover, phytoplankton also had an important influence on zooplankton.(4) The community structure of zoobenthos in the Weidoushan Reservoir was comparatively single, with a total of 12 zoobenthos, including eight hydrophily insects,three Oligochaeta and one other species. Average density of zoobenthos was 158.7 ind/m2 and average biomass was 0.6395 g/m2. Hydrophily insects made an outstanding contribution for the standing crop of zoobenthos, with its average abundance and biomass of 147.3 ind/m2 and 0.6329 g/m2, respectively. Community structure of zoobenthos was closely associated with WT, DO and NO2--N according to Pearson correlation analysis.(5) Several parameters including biomass, dominant species and diversity index of plankton and biology pollution index(BPI) of zoobenthos were used to assess the water quality, and results showed the Weidoushan Reservoir could be classified as oligo-mesotrophic.