| Lake Changdang is located in Changzhou city,Jiangsu province,the two city Jintan and Liyang were crossed.It is one of the typical,small and shallow lakes in the middle and lower reaches of the Yangtze river.With the development of society and economy,the influence of production and business on Changdang Lake is growing.In recent ten years,the degree of eutrophication in Changdang Lake was increasted,and the ecological steady were threated unprecedentedly.In addition,Changdang Lake is the water source of the Jintan and Liyang,the ecological environment and water quality are relate to the sustainable development of economy.This study aimed to conduct an investigation about the present situation of ecological environment of Changdang Lake,at the same time,the natural bait was measured,and the plan of appropriate range in Changdang Lake was put forward on this basis.In order to provide reliable data support and reasonable suggestions for the protection of ecological environment and the planning of fishery in Changdang Lake.The following is the results of this research:1.The result of investigation for ecological environment show that the average of single pollution index of the TP at each sampling point was 1.64,the average of single pollution index of the TN was 2.64.The variation range of the Carlson trophic state index at each sampling point was 53.17?63.79,the average of the index of comprehensive nutrition state was 59.03.Considering the content of N,P and the Carlson trophic state index,the water quality of Changdang Lake did not reach the standard of III class water quality,and the water in a state of light pollution.2.In the survey,7 phyla,61 genera and 96 species of phytoplankton were identified.The chlorophyta 40 kinds,bacillariophyta 21 kinds,cyanophyta 20 kinds,euglenophyta 9 kinds,Cryptophyta 3 kinds,pyrrhophyta 2 kinds,chrysophyta 1 kinds were contained,and the total of dominant species was 11 kinds.The density of phytoplankton was 4.09×106?2.82×10~7 ind./L,the average density was 1.61×10~7 ind./L.The variation range of phytoplankton biomass was 2.82?15.13 mg/L,the average biomass was 6.92 mg/L.The range of Shannon-winer index for phytoplankton was 3.80?4.75,and the mean value was 4.34;The change range of evenness index was 0.66?0.84,and the mean value was 0.76;The change range of Richness was 1.92?2.75,and the average was 2.30.Comprehensive three evaluation index of phytoplankton,we considered that the diversity of community structure in Changdang Lake is good.3.In the survey,4 phyla,26 genera and 42 species of zooplankton were identified.The rotifera 6 kinds,protozoan 15 kinds,copepoda 7 kinds,cladocerans 4 kinds were contained.The range of density was 4.00×10~3?3.86×104 ind./L,the average density was 8.84×10~3 ind./L.The variation range of biomass was 0.37?2.69 mg/L,the average biomass was 1.13 mg/L.The range of Shannon-winer index was 1.05-2.49,and the mean value was 2.03;The change range of evenness index was 0.50?0.71,and the mean value was 0.65;The change range of richness was 0.41?0.90,and the average was 0.64.In addition,4 class and 12 kinds of benthonic animal were identified,and the range of density was 40.00?720.00ind./m2,and the average density was 175.39 ind./m2;The change range of biomass was 0.012?12.37g/m2,and the average biomass was 2.09g/m2.4.The result of survey for Fishery resources show that 17 types of fish were caught,which belonging to 3 orders 3 families 14 genera,Carp shape mesh fish occupied absolute advantage in catches.There are five kinds of dominant species,Hypophthalmichthys molitrix,Coilia nasus,Pseudobrama simoni,Parabramis pekinensis and Carassius auratus.The richness index(R)of community of catches was 2.57,the index of information(H')was 1.90,the index of dominance(D))was 0.21,the index of evenness(E)was 0.67,Comprehensive four evaluation index of diversity,we considered that the diversity of community structure of catches in Changdang Lake is relatively single.5.Through the theoretical calculation,the potential fishery productive capacity of phytoplankton in Changdang Lake was about 1146.99 tons,the potential fishery productive capacity of zooplankton in Changdang Lake was about 842.84 tons,the potential fishery productive capacity of large benthonic animal in Changdang Lake was about 44.41 tons,the potential fishery productive capacity of organicdebris in Changdang Lake was about 994.92 tons,total potential fishery productive capacity was about 3030 tons.If grazing fish according to the specifications of the 0.1 Kg,could calculate the theory of grazing of Hypophthalmichthys molitrix and Aristichthys nobilis were 1,020,000 and 750,000 respectively,the ratio of grazing was close to 4:3. |
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