Construction And Evaluation Of Ecopath Model Of The Ecosystem Of Lake Wuli

Lake Wuli is also named Li Lake, which is the one shallow bays of Lake Taihu. it is located in the city Wuxi. It play an important role in sources of drinking water; industry, agricultural irrigation, landscape and entertainment.In order to evaluate the stocking filter-feeding organisms how to affect the ecosystem, inview of the three existing aquatic ecosystem modeling approach(single-population model, multi-species virtual model and based on the food web ecosystem model what’s name is EwE model), Ecopath with Ecosim is designed for straightforward construction, parameterization and analysis of mass-balance trophic models of aquatic and terrestrial ecosystems.it has become a useful tool for marine fisheries and freshwater fisheries to manage and analyze the ecosystem.The ecology of Wuli Lake are studied for four years, the value of DO and TN was significantly decreased, The water’s quality in the lake is improved.Using the Ecopath with Ecosim software beta6.0, constructed the ecopath model of Lake Wuli in2009. The model consists of17functional groups, which are Large culters, Other piscivorous, Tapertail anchovy, Common carp,Crucian carp, Bighead carp, Other fishes, Silver carp, Herbivorous fishes, Macrocrustaceans, Molluscs, Other benthos, Zooplanktons, Submerged Macrophytes, Other macrophytes, Phytoplanktons, Detritus. Through network analysis, Trophic levels of the compartments vary from1.00for the primary producers and detritus to3.958.The system net work is mapped into a linear food chain and six discrete trophic levels are found with a mean transfer efficiency of4.8%from detritus and4.1%from the primary producers within the ecosystem. The geometric mean of the trophic transfer efficiencies is5.7%.In the course of energy flow, the proportion of total flow originating from detritus is60%.and that from the primary producers is39%.The parameters of this ecosystem:Total primary production/total respiration (TPP/TR), Connectance Index (FC), Ascendeancy(A), Finn’s cycling index(FC), Finn’s mean path length (FCL)and System Omnivory Index(SOI) are:1.154,0.243,0.292,0.168, 3.909,0.106respectively. The result indicated that the ecosystem of Lake Wuli inclines to mature at present and the connection is loosening. Stocking filter-feeding fish has significant downstream effects on ecosystem of lake wuli, which the distribution of other functions in a smaller group of organisms within trophic levels. Enhanceing the biomass of filter-feeders fish, increasing the number of ferocious fish and planting aquatic plants are suggested to increase the biological stability of the lake ecosystem.Three ecopath models are established on lake wuli ecosystem which based on three periods which are early (2006)、medium (2007)、lately (2009) what are sorted by filt-feeding fish is stocking. Connectivity index (CI) of the ecosystem of Lake Wuli, in three models, is inchanced year by year. This conclusion tells us that the nutrient within the lake wuli is gradually recycled; TPP/TR of lake wuli ecosystem are1.154(2006)>1.339(2009)>1.220(2007), which indicated the ecosystem is in lowly maturing.the main reson is that the biomass of Consumers is higher than that of producers.The Finn’s cycle average flow pathlength (FCL) were:3.909(2006),3.436(2007),3.393(2009). through MTI analysis,some conclusion are obtained: bighead carp positive impact on the ecosystem than their negative impact on the ecosystem,on contrary, silver carp has the opposite affect. Filter-feeding shellfish has positive impact on the ecosystem is less than the number of functional groups negatively affected the number of functional groups; niche overlap in the point of view, silver carp, mollusks greater impact on the ecosystem, the bighead carp and other basic feature set has not changed.The total ecosystem characteristics of Lake Wuli System of primary productivity, total respiration (TR), the total flow of detributs (TDE), the total production (TP) and the system through output are rising year by year. The over all productivety of lake wuli is greatly improved.