Seasonal Dynamics Of The Community Structure Of Plankton And Zoobenthos In Lake Chaohu

With the development of social economy, lake eutrophication has become worseand worse. It turned to be one of the environmental problems in the word, whicheventually resulted in the serious degradation of service functions. As the importantfunctional group in lake ecosystems, plankton and macrozoobenthos played animportant role in material cycling and energy flow. Plankton and macrozoobenthoscommunity were investigated in Lake Chaohu. Furthermore, the relationshipsbetween plankton, macrozoobenthos community and environmental variables wereanalysed. This study achievements will provide scientific basis for controlling nutrientrelease, eutrophication management. The main results were as follows,(1) A total of118species of phytoplankton were recorded, which belonged to56genus,27families and6phylum in Lake Chaohu. The number of species was higherin June and September than in March and December. The density of zooplankton wasfound highest (34.20±8.88（×107） ind./m2) in September and lowest (13.74±7.44（×107）ind./m2) in December. The density of zooplankton showed markeddifferences among different months （F0.05(3,60)=2.81，P<0.05）. There was nodifferences between in June and September, the same as in in March and December.However, the density of zooplankton between in June and Septembe weresignificantly different.(2) A total of23species of macrozoobenthos were recorded, which belonged to8families,5classes and3phylum in Lake Chaohu. The dominant species wereClinotanypus sp., Microchironomus sp., Limnodrilus hoffmeisteri, Tanypus chinensis,Tubifex tubifex, Branchiura sowerbyi, Bellamya aeruginosa. The dominant speciesvaried in the western lake areas and eastern lake areas. The eastern lake areas weredominated by Clinotanypus sp. and Microchironomus sp., while the western lake areas were dominated by Limnodrilus hoffmeisteri, Tanypus chinensis, Tubifex tubifex.The species richness in Lake Chaohu was fewer. Only one species of snails wasrecorded in Lake Chaohu. Snails were mainly distrbibuted in macrophyte-dominatedlake areas. Thus, the disappearance of macrophytes was responsible for the decreasingspecies richness of macrozoobenthos in Lake Chaohu.(3) A total of24species of rotifers were recorded, which belonged to13genus,9families and6phylum in Lake Chaohu. A total of32species of planktoniccrustaceans were recorded, which belonged to22genus,11families,4classes and2suboreders in Lake Chaohu. The number of species was higher in summer and autumnthan in spring and winter. The density of rotifers was found highest (975±298.5ind./l)in June and lowest (123.5±54.5ind./l) in April. The density of planktonic crustaceanswas found highest (0.447±0.279ind./l) in September and lowest (0.016±0.006ind./l)in April. The density of rotifers and planktonic crustaceans showed markeddifferences among different months (P<0.05）. The density of the rotifers was nodifferences between in June and September, the same as in June and December, thesame as in September and in April. However, the density of rotifers between in Juneand December were significantly different, the same as in September and April. Thedensity of the planktonic crustaceans was no differences between in June andSeptember, the same as in December and in April. However, the density of planktoniccrustaceans between in June and December were significantly different.