| In this paper, water quality of ecological cage culture area and non-cultured area in Longtan Reservoir were investigated from July to December in 2010, also fish feces in the collected were examined. ANOVA were used to analyze the differences between the surface and bottom water in the ecological cage,between cage culture and reservoir water,among the water of three different cages,respectively. The results were as follows:1. There were no significant differences between the surface and bottom water of the ecological cage; The water temperature,pH,DO were ranged from 19.5 to 30.7℃,from 7.99 to 8.80 and from 4.76 to 8.71 mg/L,respectively. Ammonia nitrogen (NH4+-N) and nitrite nitrogen (NO2--N)was only a small proportion of the total inorganic nitrogen (TIN);The nitrate nitrogen (NO3--N) was not only the main part of TIN, but also a major component of total nitrogen (TN).The double nested ecological cage has a sewage collection device. Algae-eating fishes such as silver carp and bighead carp lived in external network, the inner were commercial fish. It can improve feed utilization, reduce the amount of food residue; the collected device could gather 2.7t dry weight aquaculture waste in one culture cycle, and inhibit water eutrophication effectively. The waste contained 2.93% crude protein,0.29%TP,0.47% TN.2. Longtan Reservoir was limited phosphorus. The content of chlorophyll a showed a significantly positive correlation with TN. Ecological cage culture can change the nutrient structure. There were no significant differences in TN and TP between water of ecological cage and the reservoir, but could reduce water eutrophication to some extent.The nutrition level of ecological cage and the reservoir were middle eutrophication, mean values were 38.1 and 37.4 respectively, but there were no significant difference between them. If the area of cage culture was at a reasonable range, ecological cage culture has no significant effect on water eutrophication.3. There were no significant differences among water qualities of traditional cage(A),ecological cage with no collected device(B) and ecological cage(C)(P>0.05). Chl. a,SD,TN and TP are chosen as indices to the eutrophication evaluation,the results was TLIA>TLIB>TLIC,and there were no significant differences among.The eco-characteristics of phytoplankton in the three different cages were studied in 2010. The results showed that 7 classes including 116 species have been founded, and the major components were Chlorophyta,Bacillariophyta and Cyanophyta. Among them, dominated Chlorophyta has 56 species, accounting for 48.2% of the total phytoplankton species, Bacillariophyta has 35 species, taken the second place, accounting for 30.2% of the total phytoplankton species, and Cyanophyta has 18 species, accounting for 15.5% of the total phytoplankton species. The ranged phytoplankton abundance from 2.16 to 31.98 ind.L-1, the order were NA>NB>NC, and there were no significant differences among them. Water body of the three different cages was regarded as middle nutrition under standards of phytoplankton abundance.The collection device of ecological cage can reduce the emissions of nitrogen and phosphorus, and effectively inhibit water eutrophication. Meanwhile compared with other cages, the waste feed and excrement of fishes resulted in the rapid growth of phytoplankton and became the pollutant source of water body. Solving this problem should be the next task. |
