Community Ecology Of Macrozoobenthos In Mingzhu Lake, Shanghai And Yangcheng Lake, Jiangsu Province

Zoobenthos play an important role in material recycling and energy flow of ecological system, the link of food webs of the bottom and water layer. Meanwhile, zoobenthos have an important application value too, such as monitoring of freshwater environment, ecosystem health assessment, fishery management, and so on. The profundal communities of macrozoobenthos in Mingzhu Lake, Shanghai had been investigated from March 2006 to December 2009, which also studied in Yangcheng Lake, Jiangsu Province in 2008 year. The main results are as follows:Forty-one macrozoobenthos species belonging to 4 phylum and 16 families were recorded in Yangcheng Lake, among which Bellamya aeruginosa and Tanypus chinensis dominated the communities of macrozoobenthos. No significantly seasonal differences in zoobentho community types were found. The primary functional feeding groups were gather-collectors and scrapers. 49 macrozoobenthos species belonging to 4 phylum and 19 families were recorded in Mingzhu Lake. Propsilocerus akamusi, Limnodrilus hoffmeisteri and Tanypus chinensis dominated the communities of macrozoobenthos. Gather-collectors dominated the functional feeding groups. There were no significant differences in zoobenthic community types among years, and were among seasons with L. hoffmeisteri and T. chinensis communities in spring and autumn, Propsilocerus akamusi communities in winter, and P. akamusi,L. hoffmeisteri and T. chinensis communities in summer. The Shannon species index was relatively lower in summer than other seasons in both of the two lakes.Annual average density and biomass were 319.9 ind./m~2 and 24.02 g/m~2, respectively, and didn’t display seasonal variation, but differed significantly spatially with the highest density in eastern lake (EB) and the lowest in tributaries (TRIB) and the highest biomass in culturing enclosures of Chinese mitten crab (Eriocheir sinensis) (CEES) and the lowest in western lake (WB). The responses of zoobenthos and its major groups to culturing of Chinese mitten crab were diverse, the farming activities led to the decrease of overall density significantly and increase of overall biomass and Shannon index, the decline of density and biomass of oligochaetes and aquatic insects and the increase of density and biomass of snails. The stepwise regression analysis showed that the major physical-chemical factors were different in explaining the spatial distribution of zoobenthos and its groups. The canonical correspondence analysis (CCA) indicated that Alocinma longicornis and Parafossarulus striatulus tended to occur at sites with larger transparency, Microchironomus sp., Chironomus flaviplumus and Bellamya aeruginosa tended to occur at sites with lower transparency and concentration of dissolved oxygen (DO), L. hoffmeisteri, L. claparedeianus tended to occur at sites with lower content of soluble reactive phosphorus (SRP).Annual average density and biomass were 2119.7 ind./m~2 and 4.60 g/m~2, respectively. Three-way ANOVA showed that density differed significantly spatially, seasonally and yearly, and biomass did seasonally and yearly, but didn’t display spatial variations. The density and biomass increased year by year, with higher values in winter compared with other seasons and lower ones at station 2 and 5 than other stations. The stepwise regression analysis showed that among physical and chemical environmental factors only water depth and water temperature could been used to explain the spatial and temporal variations of zoobenthic density and biomass. The canonical correspondence analysis (CCA) indicated that water temperature was key factor responsible for the spatial and temporal distribution of P. akamusi and C. flaviplumus, and water temperature and water depth for that of L. claparedeianus.The comparison analyses of the data collected monthly and seasonally in Mingzhu lake indicated that there were no significant differences in zoobenthic communities calculated by monthly and seasonal data, as well as density and biomass, however, markedly differences were found in Shannon species index and species number. The results showed that only seasonal sampling would be enough when investigation will aim at community types and the total density and biomass of macrozoobenthos in Mingzhu Lake, but the monthly sampling should be done when the objectives will focus on the biodiversity of macrozoobenthic community.The dominant species in Yangcheng and Mingzhu Lake were tolerant species. Shannon species index and Carlander’s biomass index were both suitable for water quality assessment of Yangcheng Lake and Carlander’s biomass index, Shannon species index and Wright index useful for that of Mingzhu Lake. The indictor species and the results of assessment showed that Yangchen Lake has become eutrophic and Mingzhu Lake has been moderately polluted. It was estimated that the secondary production of major species in Yangcheng and Mingzhu Lake were about 27.83 and 21.91 g/m~2/a, respectively, and the whole-lake fishery potentials were about 1.09×10~5 and 1.10×10~4 kg.