Studies On The Community Structure And Biodiversity Of Plankton And Zoobenthos In Miyun Reservoir

The composition, population density, biomass and dominant species of zoobenthos communitystructure were analyzed through the zoobenthos sampling in Miyun Reservoir. In combination with theresults of simultaneous determination for the main physical and chemical indicators of Miyun Reservoir,the impact factors that affect the distribution of the zoobenthos in Miyun Reservoir were analyzed, andthe biodiversity of the zoobenthos was analyzed, and the water quality was evaluated for MiyunReservoir based on these. At the same time，the community structure, population density, and variationrule of phytoplankton，and zooplankton were analyzed through the phytoplankton and zooplanktonsampling in Miyun Reservoir. The biodiversity index and dominance of rotifer were analyzedsimultaneously for Miyun Reservoir; the water quality was evaluated according to the algae cell density,rotifer biodiversity index, and comprehensive trophic state index of Miyun Reservoir. Finally theeffectiveness of the evaluation for water quality state of Miyun Reservoir by the application ofzoobenthos biodiversity was analyzed through the results of the several different methods.The results of study showed that:（1）The zoobenthos community was composed of15species inMiyun Reservoir, including10species of chironomid larvaes, and5species of oligochaetes. Thebiomass of zoobenthos was3.94g/㎡, the density was395.7ind/㎡, in which the dominant speciesinclude tubificids Tubifex, T.gr.plumosus, Chaetocladius sexpapilosus. The seasonal change of biomassand density was distinct, in which it reached its maximum in April and minimum in July.Shannon-Wiener species diversity index was1.49for an average. The biological evaluation was carriedout for the reservoir ecosystem according to the Shannon-Wiener species diversity index of zoobenthosin Miyun Reservoir, and the waters in the bottom of Miyun Reservoir was in the middle pollution levelas a whole.（2）The phytoplankton in Miyun Reservoir was composed of7Phylums, and71genera（species）. The cell density of the phytoplankton was464.55x10⁴cells/L, and the variation range wasfrom322.24x10⁴cells/L to640.59x10⁴cells/L. The peak value of the cell density appeared in September,and the lowest density in May. Refer to the density of phytoplankton, Miyun Reservoir was in themiddle pool trophic type based on the algae biological indicators （the middle pool nutrition was in1.0x10⁶cells/L⁹.0x10⁶cells/L） evaluated by the lake trophic type.（3）The zooplankton community ofMiyun Reservoir was composed of17species of protozoas,37species of rotifers,12species ofCladoceras, and5species of Copepoda with a total of71species. The average density of zooplanktonwas27.2ind/L in April, and76.8ind/L in May. The average index of rotifer biodiversity was1.91inApril, ranging from0.84-2.92; and2.50in May, ranging from0.66-3.32. The water quality of MiyunReservoir was in a medium pollution level evaluated by Shannon-Wiener index of the rotiferbiodiversity.（4）The results of sampling and determination of the physical and chemical indicators forMiyun Reservoir showed that all of three indicators, i.e., the dissolved oxygen （DO）, permanganateindex （KMnO₄）, and chemical oxygen demand （COD） reachedⅠtype of water quality standards; the total phosphorus （TP）, ammonia （NH4+-N）, and biochemical oxygen demand （BOD5） reached II typeof water quality standard; and the total nitrogen （TN） reached III Type of water quality standard. Thetrophic state of the waters of Miyun Reservoir was in mesotrophic state level evaluated bycomprehensive trophic state index method.The conclusions of study showed: the water quality of Miyun Reservoir was evaluated by thebiodiversity of zoobenthos, rotifer biodiversity index, and comprehensive trophic state index,respectively, and the results of the evaluation were consistent, showing the water quality of MiyunReservoir was mesotrophic level; if the cell density of phytoplankton alone as a basis for the waterquality evaluation, the water quality of Miyun Reservoir was in middle poor trophic level. Based on theabove aspects of the findings, the conclusions could be drawn that the biodiversity index of thezoobenthos could exhibit more completely the overall status of the waters of Miyun Reservoir, andobjectively responsed the dynamic change process of the water quality in Miyun Reservoir over alonger period.