Experimental Study Of Landscape Lake Eutrophication Based On Three Trophic Levels

Landscape lake has a dual function of landscape and ecology.It has an important significance for improving the urban ecological environment,the quality of life and happiness index.However,landscape lake eutrophication not only damage the environment and bring visual pollution,but also aggravate the contradiction of water shortage,restricting the regional development.This study based on the theory of eutrophication,adopting method of microcosm simulation and taking the lake in Tianjin University of technology as the study object.Studying the mechanism and the effect of eutrophication by the compose of different trophic levels in landscape lake.Microcosm system and experimental scheme are designed by measuring the study area and consulting literature.The design of microcosm includes aquarium size,system scale,lighting system,aeration system and temperature control system.The design of experimental scheme are composed of trophic levels,experimental time and main measuring items in raw water experiment and allocative water experiment.Raw water experiment carried out 35 days,it is divided into two stages.The first stage has one trophic level and two trophic levels.The second stage has one trophic level and three trophic levels.Allocative water experiment carried out 28 days and it has one,two and three trophic levels at the same time.The main measuring items include TN,NH3-N,NO2-N,NO3-N,TP,phosphate,chl-a,temperature,pH,DO and turbidity.By carrying out experiments and analyzing the results,we can draw the following conclusions.The change of chl-a and nutrients in one trophic level and two trophic levels are totally close,and the diffierences between them are not significant.But it has a significant difference between one and three trophic levels.It shows that carps have a significant impact on phytoplankton biomass and water nutrient concentration,especially on NH3-N,NO3-N and phosphate.One trophic level system has a better reduction effects of nutrients.Two trophic levels system has a better control effects of chl-a and turbidity.Three trophic levels has a great control of nutrient concentration and a better water stability.Limiting factors are found by correlation analysis through the SPSS.Measures and suggestions to control eutrophication are proposed based on the analysis of experimental results.Eutrophication hazards could be controled or limited on the one hand by adding carp,silver carp,bighead carp and other plant-feeding fish to increase zooplankton biomass,on the other hands by controlling the concentration of nitrogen expecially NO2-N in one and three trophic levels landscape lake and NH3-N and phosphate in three trophic levels lake.By monitoring the change of pH in water,we can find the eutrophicated trend of lake earlier and take appropriate measures to inhibit its occurrence.