Inhibitory Effects Of Two Ornamental Aquatic Plants On Microcystis Aeruginosa

Firstly,this paper summarizes several key points about eutrophication,including the definition of eutrophication,the domestic eutrophication status of lakes and forming mechanism of algal blooms caused by eutrophication.Secondly,the general technique development via using aquatic plants to inhibit algae at home and abroad is introduced.Finally,this paper discusses the technical principles of inhibition of algae by aquatic plants.This article selects two kinds of wetland landscape plants-Pontederia cordata and Cyperus alternifolius L.,widely used in landscape gardening and investigates the effects of different plant water concentrations on the growth of Microcystis aeruginosa(a typical species of Cyanobacterial blooms).Moreover,the inhibitory impact on the growth of Microcystis aeruginosa with different plant water concentrations is compared.The plant water concentration yielding the strongest inhibitory effect would be selected as the condition to culture Microcystis aeruginosa,and inhibiting effect would be observed and the associated mechanism would be studied.The main experimental results are as follows:(1)Both Pontederia cordata and Cyperus alternifolius L.planting water could impose certain inhibitory effects on algal growth.The inhibitory effects of Pontederia cordata and Cyperus alternifolius L.on algal growth strengthened as the concentrations of planting water increased,and the inhibitory effects was related to the density of algae.The lower the initial algal density was,the higher the relative concentration of the allelochemicals was,and the inhibitory effect is more obvious with the shorter inhibition time.The continuous addition experiment with Pontederia cordata and Cyperus alternifolius L.planting water revealed that the algal inhibiting effects was increased along with the planting water addition.The concentration of Pontederia cordata with the strongest inhibitory effect was 166.7 FW g/L with the median effective concentration of 116.97 FW g/L,and its biggest algal inhibiting efficiency was 49.89%.The concentration of Cyperus alternifolius L.with the strongest inhibitory effect was 12.5 FW g/L,and its median effective concentration and biggest algal inhibiting efficiency were 9.93 FW g/L and 88.08%,respectively.(2)Cyperus alternifolius L.significantly inhibit Microcystis aeruginosa growth under the co-culture condition.The results revealed that the algal density of Microcystis aeruginosa decreased significantly,and yellow sediment was observed in the bottom of device with an obvious solid-liquid layer.Several physiological and biochemical indexes was determined under the co-culture condition,including chlorophyll a content,MDA content,SOD activity,CAT activity and GSH concentration.The results demonstrated that the decrease of algal density was directly related to the activity of antioxidant system of algal cells.Through the analysis of these physiological indexes,the inhibition mechanism of Cyperus alternifolius L.on Microcystis aeruginosa growth was explored.Cyperus alternifolius L.could release allelochemicals to inhibit activity of antioxidant enzyme system in algal cells,and thus the alga could not scavenge intracellular free radicals,leading to that highly reactive and toxic free radicals could react with algal cells,terminating the algal growth,and the algal cells then died.