Analysis On Fish Community And Ecosystem Structure In Lake Kuilei

Lake Kuilei is the strategic water source area in Kunshan city. For the purpose of attempting ecological restoration to improve water quality, the research was needed to survey and analyze the existing biological component of the lake ecosystem whether reasonable, and the advice how to manage and control the biological component in the lake were put out.Therefore, from September2009to December2010. in addition to species composition of fish community, phytoplankton, zooplankton, benthos and aquatic macro-phytes in Lake Kuilei, seasonal variation and spatial distribution of density and biomass were investigated,then the relationships between biological components and environmental factors were analyzed.The results were as follows:26species fish belonging to9families were found in the fish catches, of which Cyprinidae was the dominant family with18species,accounting for69.23%of total fish species:Hypophthalmichthys molitrix and Aristichthys nobilos became the dominant fishes in the lake,respectively accounting for (20.82±8.06)%,(41.58±19.24)%of the total fish catches; in the diet composition of the dominant fishes, the dominant species, H. molitrix and A.nobilos mainly fed on phytoplankton,i.e.Cyanophyta and Bacillariophyta.and partly fed on zooplankton.namely Cladocera.while the carnivorous fish(Elopichthys bambusa and Culter alburnus) mainly fed on fishes and shrimps. The status of fewer fish species in the lake was possibly caused by species singularity of releasing fish fry and the competitiveness of E. bambusa to other fishes; high fish biomass was mainly caused by the excessive number of A. nobilos put in; and the quantity of demersal fishes was large.52species from7genera of phytoplankton were identified in Lake Kuilei. The dominant species were Merismopedia glauca, Phormidium tenue, Cyclotella sp., Aulacoseira granulata. A. ambigua. Asterionella formosa, Synedra acus. Scenedesmus quadncauda, Chlorella vulgaris, Cryptomonas eros. Chroomonas acuta and Dinobryon divergens). Differed from the PEG Model, the seasonal succession of phytoplankton community structure in Lake Kuilei was from the winter to early spring being mainly for Chlorophyta and Cryptophyta, Cyanophyta of great abundance occurring at the end of spring, then dominating in summer and the early autumn, namely the growth time of Cyanophyta in Lake Kuilei was greatly extended, which was a sign of eutrophication.29species of crustacean including17species of Cladocera, and12species of copepoda were found in Lake Kuilei. The common dominant species were Bosmina coregoni. Moina micrura. Diaphanosoma brachyurum, Limnoithona sinensis, Cyclops vicinus, Mesocyclops leuckarti, Thermocyclops taihokuensis. Sinocalanus dorrii. Schmackeria forbesi. The biomass of crustacean is the highest in July (0.593mg/L), and is the lowest in February (0.013mg/L). The density of crustacean is the highest in July (44.7ind./L). and is the lowest in January (0.9ind./L). Correlation and regression analysis of planktonic crustacean community structure and environmental factors showed that temperature and DO were strongly correlated with the crustacean community structure.The density and biomass of crustacean showed a significantly positive correlation with temperature and a significant negative correlation with DO.In Lake Kuilei a total of32benthic species were found, among which Chironomidae was the most with12species; Mollusca took second place with11species.including6species of gastropod and5species of bivalve; the aquatic oligochaete were few with4species;other type had5species, like Gammarus.nematoid and so on.The dominant species of density were Propsilocerus akamusi Tokunaga. Limnodrilus hoffmeistteri and Bellamya. respectively accounting for25.38%.18.97%.and17.18%of the total density. The dominant species of biomass were Bellamya, Parafossarulus eximius. Alocinma longicomis and Corbicula fluminea, respectively accounting for75.74%.11.86%,3.24%and5.38%of the total biomass. The average density of benthos is909ind./m2, and the average biomass was257.95g/m2in Lake Kuilei. Synthesizing the evaluation criteria of Goodnight index. BPI biology index, the Shannon-Wiener index, there was a judge that the water quality was good at present stage in Lake Kuilei. which was in the light-secondary pollution level, and was in the early stages of eutrophication.The distribution of aquatic macrophytes covered an area of1.175km2, which were composed by emerged macrophytes, submerged plant and leaved macrophyte. accounting for17.54%of the whole lake area. The emerged macrophytes were mainly by Phragmites communis, Acorus calamus, Typha angustifolia,Kobresia as well as Zizania caduuciflora, and mainly distributed in the shallow water area of the lakeside. The submerged plant were mainly for Myriophyllum, Ceratophyllum demersum. Vallisneria spiralis, Potamogeton malainus and so on. and mainly distributes in the center of the lake area, in the southeast of Northeast of L-shape dam. in the north side of south of T-shape dam and the few lake area of west side.The leaved macrophyte were mainly for Trapae Quadricaudatae and Nymphoides peltatum. which scattered in the lake, but a small amount of leaved macrophyte distributed in north side of Eastern Island of the south of Lake Kuilei Island.