Study On The Performance Of Submerged Plants Under Low Light And The Ecological System Analysis Of Shapingba Park Lake

Water ecological restoration technology has been widely used in eutrophic drainage basin,such as lake and reservoir、river basin,and obtained a certain effect.Submerged plant as one of the important member in lake ecological system,has significant influence in the water ecological restoration.The submerged vegetation restoration and reconstruction in the deep lake is mainly restricted by low light factors,so the experimental part of this article is mainly through the tubular daylighting system to build a low light intensity changes in a row,and research the performance of typical submerged plant in southwestern lakes.Meanwhile,the main water ecological restoration engineering in Shapingba Park lake is Purely Ecological Control Technology,and the lake ecological environment changed.So Ecopath ecological model is presented in this paper,to analyze the water quality changes after one year of the modification in Shapingba Park lake,and research the newly formed nutrition structure,food chain of energy flow,mature degree and stability of ecosystem in Shapingba Park lake.(1)The light transmission performance of tubular daylighting system is good,the average transmission efficiency is 70.0%.Underwater light intensity(tI)and the linear distance from tubular daylighting system(t)in line with the Beer’s law,the regression equation is:-0.023xy=5840.6e,n = 16,R2 = 0.9871.(2)In the low light conditions,three kinds of submerged plants have certain purification effect on water quality under combined action of V.spinulosa Yan 、V.natans Hara and Hydrilla verticillata,on the removal rate of NH3-N is highest,at 60%,and the lowest level of CODcr removal rate is 46.90%;at the end of the experiment,the residual water of the submerged macrophytes was decomposed by low light,which led to the increasing trend of conventional water quality.(3)In addition to the points of index,the plant dry weight and plant length of 3 submerged plant、 root length and leaf number of V.spinulosa Yan and V.natans Hara、as well as the distance between leaves and numbers of stem nodes of Hydrilla verticillata、 are decreases with the decreasing of light intensity.When the illumination percentage are 0.5%,2% and 0.5% respectively,the other growth indexes of 3 submerged plant appeared the trend of rapid attenuation.In addition,the attenuation trend in dry weight and plant length index of 3 submerged plant: Hydrilla verticillata > V.natans Hara > V.spinulosa Yan,that Hydrilla verticillata received the inhibiting effect is more obvious.(4)The farther the distance from the light guide system,the lower the light intensity.With the loss of the light intensity,V.spinulosa Yan 、V.natans Hara and Hydrilla verticillata three kinds of submerged plant photosynthetic pigment parameter values are showing a declining trend,showing that the submerged plant photosynthesis are under stress,the degree of stress: Hydrilla verticillata > V.spinulosa Yan > V.natans Hara.With the loss of the light intensity,Hydrilla verticillata is the stress function of MDA significantly at first,Followed by V.spinulosa Yan,V.natans Hara.stress effect is not obvious,the content of SOD and POD enzyme levels of three kinds of submerged plant are rising as the light intensity,showing that three kinds of submerged plant under low light conditions are in adversity,and Hydrilla verticillata and V.spinulosa Yan are changing more significantly than V.natans Hara of the SOD.(5)The water quality in Shapingba Park lake has been developed from the surface water environmental quality of bad Ⅴclass into Ⅴ class water standards after water ecological restoration.The Ecopath model of Shapingba Park lake ecological system,includes 14 functional groups which contains the primary producers、consumers and clastic.The ecological system has 4 valid trophic level,which ranges 1 ~ 3.092 and the functional groups of nutrition conversion efficiency between 0.063 ~ 0.998.The trophic level arranged in the pyramid system flow,and Energy flow is distributed in pastoral food chain and rotting food chain two ways,accounting for 58.34% of the total flow,58.34% respectively.The total system energy conversion efficiency is too low,only 2.0%.The ratio of net primary production and total volume(TPP/TR),connection index(CI),omnivorous index(SOI),the Finn ’s circulation index(FCI),the Finn’ s average path length(FML)were 1.945,0.281,0.052,and 2.499 4.070% in Shapingba Park lake ecosystem.Through the comprehensive analysis of these parameters,Shapingba Park lake ecosystem’s the stability is not high,food webs is simple,and the ecosystem Vulnerable to external disturbance easily and is in the early development and immature ecosystem.