Microcosm Experimental Study On The Impact Of Tilapia On Landscape Lake Water Quality

Landscape Lake is an important component of urban construction,and its water eutrophication is worsening day by day.In recent years,biological manipulation has been highly valued by academics both at home and abroad in various means of eutrophic water restoration.In this paper,the tilapia was selected as the research object to simulate the eutrophication of the landscape lakes in the natural environment by using the aquarium microcosm system.The effects of tilapia stocking on the water quality nutrients and phytoplankton biomass in landscape lakes were studied.In addition,tilapia waste collection and determination were also carried out to analyze the composition of excrement nutrient and the effects of excrement on landscape lake water quality nutrients and phytoplankton biomass.So as to provide a reference for the mechanism of the biological manipulation of omnivorous fish and feasibility analysis and provide data support for the establishment and improvement of the eutrophication model.Through the analysis of the experimental results,we can draw the following conclusions:In the microcosm system of tilapia stocking,the pH of the water body increases and the higher the stocking density,the higher the pH value of the water body.Compared with the control group,the turbidity of the water body in the fish-releasing system firstly decreased and then increased,the turbidity of high-density group increased rapidly,which was much higher than that in the low-density group.The total nitrogen and total phosphorus nutrition levels showed a downward trend to varying degrees,and other nutrients such as ammonia nitrogen,nitrate nitrogen,nitrite nitrogen and phosphate also declined.In both low-density and high-density groups,total nitrogen is dominated by organic nitrogen,while inorganic nitrogen is mainly nitrogen-based,with less nitrogen and nitrite nitrogen.The correlation analysis showed that TN and NH₃-N were positively correlated.Tilapia excreted nutrients mainly nitrogen nutrients,of which organic nitrogen is the main form,while inorganic nitrogen in the highest ammonia content.Tilapia excrete phosphorus nutrient content is low,the vast majority of the form of phosphate,accounting for 85.14%of total phosphorus.In the microcosm system containing tilapia faeces,turbidity and chlorophyll a showed the same trend,both increased compared with the control group.The pH fluctuation ranged from 7.29 to 8.01,all within the optimum pH range for algal growth.Dissolved oxygen initial concentration of 9.22±0.007 mg/L or so,showing a downward trend,in most cases,the experimental group dissolved oxygen concentration was lower than the control group.The change of nutrients is relatively small,in which the content of nitrogen nutrient is increased,while the change of phosphorus nutrient is reduced on the contrary.In summary,tilapia feeding can reduce phytoplankton biomass.However,long-term stocking of tilapia with high-density will accelerate the eutrophication of water due to excretion of algae in large numbers to excrete water.Obviously the downside is stronger.However,due to the limitations of experimental scale and data volume,the use of tilapia to control bloom is still to be discussed.