The Research On The Degradation Mechanism Of Guangxi Lingshui Karst Ecosystem Of Submerged Macrophytes

Lake ecosystem is valuable natural resources of mankind,with the accelerated development of human society,The lake ecosystem in China shows a trend of degradation,reflected in the continuous decline in water quality,lake eutrophication is becoming more and more serious,and biodiversity is gradually decreasing.Among them,lake submerged vegetation degradation is one of the main problems of lake ecosystem in China.Lingshui lake is a typical representative of karst ecosystem,in recent years,with the rapid development of industrial and agricultural production areas around lake water and artificial aquatic breeding,water ecological system gradually changed,while the water quality can meet the quality standards for water sources,but the aquatic vegetation area disappeared,local residents worried about water quality.In this paper,through the collection of water quality of Lingshui lake physical and chemical indexes,planktonic animal,periphyton,submerged vegetation and rainfall in Wuming District in recent ten years and other relevant information,through the ecological environment investigation and historical data investigation and assessment of Lingshui Lake,according to the catastrophic shifts in ecosystems,this paper proposes the hypothesis that the water quality is poor and that the Wuming river flows back during heavy rainfall and has an important influence on the extinction of submerged macrophytes.The influence mainly exists in two aspects:one is a large amount of nitrogen and phosphorus in the Wuming River into the Lingshui Lake,led to the rapid growth of Lingshui Lake periphyton.This has a negative effect on the growth of submerged vegetation.On the other hand,rainwater intrusion make Wuming River to carry large amounts of sediment inflow Lingshui lake,lake water is the karst water ecosystem,water with high calcium and high HCO₃^-characteristics,in this special water environment,accelerate the flocculation of suspended particulate matter,thus impeding the growth of submerged plants.In order to verify the above hypothesis,this study carried out on the in situ water physicochemical simulation of karst ecosystem index detection and laboratory research,to explore the mechanism of Lingshui Lake disappearance of submerged vegetation.The conclusions are as follows:The lake water collected historical data show that over the past five years:Lingshui Lake Ca²⁺ and HCO₃^-concentration increasing,and through the research on planktonic animal show that Lingshui planktonic animal communities in a single species,the biomass is low.The Lingshui lake algae attached to submerged plant communities was analyzed.The different growth status on periphyton species of Vallisneria leaf has a large gap,and the number of species is less.The ecological system of indoor simulation experiment,under the same nitrogen and phosphorus conditions,exogenous Ca²⁺ and HCO₃^-were added can promote periphyton growth;in the same nutritional conditions of nitrogen and phosphorus,Ca²⁺ and HCO₃^-at the same time with the same combination of nitrogen and phosphorus in the basin under the ecological conditions with Ca²⁺ and HCO₃^-increasing concentration gradient algal biomass increased attachment.In high calcium and high HCO₃^-karst water environment although nitrogen and phosphorus concentration is low but also can cause substantial growth of submerged plants attached to the surface of algae,periphyton biomass instead of high nitrogen and phosphorus conditions will increase but the increase rate is low when the concentration of nitrogen and phosphorus is high,external environmental factors of small disturbance are likely to cause the system steady change,poor water quality in the Wuming river near water intrusion will pollute the material into water lake,Lingshui attached algae blooms,which may leads to the spirit of water Vallisneria die,make water the grass type lake steady-state conversion to algae steady state.In the flocculation of suspended particles in the indoor simulated ecosystem barrel turbidity and conductivity of the setting of the measurement,with the increase of Ca²⁺ and HCO₃^-concentration gradient,the conductivity decreased also increased;in the measurement of turbidity,Ca²⁺ and HCO₃^-ecological barrel concentration gradient high turbidity decreased faster than the earlier.