Study On The Influence Of Important Physical And Chemical Factors On The Growth Of Algae In The Alpine Travertine Karst Area

Huanglong,a scenic spot characterized with high altitude(3145-3578 m)and perennial low temperature,is well known for its depositional physiognomy and colorful travertine landscape.In recent years,algae grow on the surface of travertine in some scenic spots of Huanglong,which seriously affects its ornamental value.In order to investigate the causes of algae breeding in Alpine karst area,and provide guidance for algae control and travertine landscape protection in Huanglong scenic area,in this project,zhengyancaichi,which is the most widely distributed algae mat,was selected as the research area.Two strains of algae,isolated from algae mat and identified as Chlorophyta,were the research objects of this subject.By analyzing the water quality data of the Zhengyan pool and the contrast color pool(Multicolored pool and Yingbin pool),it is determined that the physical and chemical factors which have significant differences with the comparison color pool are the content of total nitrogen,total phosphorus and bicarbonate content in the water of the color pool.The growth parameters(growth rate,biomass,element content),photosynthetic parameters(chlorophyll content and chlorophyll fluorescence parameters)and morphological changes(micromorphology and ultrastructure)of two green algae were measured and observed under different nitrogen and phosphorus concentrations and ratios,the limiting concentration of nitrogen and phosphorus and the optimal concentration of nitrogen and phosphorus were studied.The effect of bicarbonate on algae growth was explored by analyzing the biomass,photosynthetic parameters and carbonic anhydrase activity under different concentrations of inorganic carbon(CO2,bicarbonate).The changes of major metabolic pathways in Chlorella vulgaris under nitrogen limitation were analyzed by transcriptome analysis The results provide a theoretical basis for the control and management of algae breeding in Huanglong water.The main results are as follows:(1)The contents of total nitrogen,total phosphorus and bicarbonate in Huanglong Zhengyan color pool were significantly different from those in the contrast color pool,and the contents of total phosphorus and total nitrogen were higher than those in the general indicators of eutrophication.Two strains of algae were isolated from the mat of zhengyancaichi and identified as Chlorella vulgaris(HL01)and Scenedesmus obliquus(HL02).When cultured at 10 ?,the two strains reached a stable period in 21-25 days.(2)In the range of nitrogen concentration selected in the experiment,the initial nitrogen concentration of 3 mmol/L(Na NO3)was the concentration limited for the two kinds of algae.At this concentration,the biomass accumulation and photosynthesis of the two algae were inhibited,and a large amount of starch was accumulated in the cells.When the nitrogen concentration was greater than or equal to 9 mmol/L,the growth rate and photosynthesis of the two species increased significantly.The most suitable concentration of nitrogen for Chlorella vulgaris HL01 was 9 mmol/L and the concentration of nitrogen surplus was 12 mmol / L;the most suitable concentration of nitrogen for Scenedesmus obliquus HL02 was 9mmol/L and the concentration of nitrogen surplus was 18 mmol/L.(3)Under the optimum nitrogen concentration,the phosphorus limit was 0.029 mmol/L(K2HPO4).Phosphorus restriction reduced the maximum light energy conversion efficiency and actual light energy conversion efficiency of algae photosystem II.The two kinds of algae accumulate a lot of starch in the cells.Under the optimum nitrogen concentration and nitrogen surplus concentration,the growth of algae was promoted by increasing phosphorus concentration.At the same phosphorus concentration,increasing nitrogen concentration was beneficial to the growth and Photosynthesis of the two species(4)Under the condition of limited CO2 concentration,the two strains could utilize bicarbonate in the culture medium by carbonic anhydrase.7-10 mmol/L of bicarbonate can promote the growth of the two algae to a certain extent.(5)Under nitrogen-limited conditions,the processes of nitrogen metabolism,protein synthesis,photosynthetic carbon fixation and starch sucrose metabolism in Chlorella vulgaris have the most changes to maintain cell survival.In summary,the results of this experiment show that the concentration of nitrogen and phosphorus nutrients has an important effect on the growth of algae,photosynthesis and intracellular substance accumulation.when the concentration of nitrogen and phosphorus is appropriate,the ratio of nitrogen and phosphorus also has an effect on the growth of algae.Bicarbonate in water can be utilized by two kinds of algae,and promote the growth of algae to a certain extent.The results suggest that the nitrogen and phosphorus content in the water can be controlled to reduce the nitrogen and phosphorus limit concentration for algae growth to control the growth of algae in the water.