| Carbonic anhydrase (CA) is widely distributed in various types of biological cells, which can quickly catalyze the conversion between CO2and HCO3-, and the CO2are an important driver of karstification. When Aquatic algae use the dissolved inorganic carbon in the water, a large amount of inorganic carbon (DIC) in karst water is converted to organic carbon to be fixed, and form a carbon sink effect. This article will choose guilin karst wetland as the study area on the basis of monitoring the water chemistry, the carbon effects of algae, microorganisms and their carbonic anhydrase are studied by indoor simulation experiment. The main research results are as follows:(1) Through the diurnal variation of water chemistry three monitoring sites(NO:1-3), and the seasonal change monitoring of water chemistry and algae in nine monitoring sites(NO:Ⅰ-Ⅸ) in Huixian karst wetland, the change rules of Dissolved oxygen, dissolved oxygen saturation, HCO3-, Ca2+, and pH are mainly studied in this paper. Results showed that the changes of DO in three monitoring sites were higher during the day and lower at night. The changes of dissolved oxygen saturation confirmed that the main performance of site2and site3were the process of synthesizing organic substances from inorganic materials in the daytime. The changing rules of HCO3-, Ca2+were different from DO’s, which were low during the day and high at night, and the monitoring sites’concentration change is1>2>3, presenting that the trend of concentration decrease along the direction of flow. The change of pH is2>3>1, which was mainly affected by aquatic plants to absorb HCO3-.The seasonal monitoring index for nine monitoring sites mainly include water temperature, dissolved oxygen (DO), pH, electrical conductivity (EC), chlorophyll a (Chl-a), blue green algae. Monitoring results show that the change of water temperature is summer> autumn> spring> winter, mainly controlled by the atmospheric temperature. The rule of DO presents winter> autumn> summer> spring, related to the photosynthesis of plants. The concentration of HCO3-and Ca2+are highest in winter, and lowest in autumn, showing that part of the HCO3" is used by aquatic plants or algae, and Ca2+decreases with temperature. Verified by electrical conductivity change, main ions in water of Huixin karst wetland is HCO3-and Ca2+. The highest pH value appears in spring, which doesn’t match the change rule of HCO3-, indicating that its change is not only affected by HCO3-, but also by large amounts of substances secreted after a plant breeding. By the relationship between blue-green algae and chlorophyll a, we found that algae were rich and relatively single in Ⅱ-Ⅳ monitoring site and in I and Ⅴ-Ⅸ monitoring site, respectively. Through calculating Primary biomass, we discover the algae-fixed carbon amount is about6196.98tC/a, amounting to75.56%of the total HCO3-.(2) Through separating and cultivating algae and bacteria of the water sampling in the Huixian wetland, and the conventional molecular sequencing identification, and using the "water-drop " method, I obtained eight algaes which could produce carbonic anhydrase, and selected the highest activity algae as the experimental materials to identify the molecules. As a result, the algae and bacteria are identified as Characium.sp and Pseudomonas alcaligenes, respectively.(3)Through the indoor simulation experiment of Characium.sp and Pseudomonas alcaligenes. Four groups were divided:the blank group (A), the bacteria (B), the algal group (C), and the bacterium and algae mixed group (D).We found the changes of HCO3-and CO2in A group were stabilized in2.8mmol/L and3.8mg/L, respectively. HCO3-and CO2in Group B elevate to3.0mmol/L and4.15mg/L, respectively. HCO3-in group C and group D reduce to1.7mmol/L and1.85mg/L. And the initial value of free CO2in group C and group D decrease from3.8mg/L to0mg/L, showing that the Characium.sp can use HCO3-and CO2at the same time, and the change of carbonic anhydrase curve can verify it. The pH changed with the change of HCO3-, and the pH in group B decrease dwith the increase of HCO3-. The pH in group C and group D increased significantly. And the Characium.sp can take advantage of HCO3-in karst water by pH compensation point. The change of HCO3-at the same time can also cause the water Ca2+change. Ca2+in group A and group B almost keep in steady state, while group C and group D largely change, and the extent of variation is21mg/L and17mg/L, respectively, which finally are almost stable at around37mg/L, showing the Characium.sp can tolerant37mg/L of Ca2+concentration. Electrical conductivity change is similar to the changes of Ca2+and HCO3-, indicating that the lower conductivity is closely related with the two ions. Dissolved oxygen is negatively in correlation with HCO3-, and the main reason is that the Characium.sp photosynthesis uses the inorganic carbon in the water, and oxygen is liberated, and at the same time the HCO3-is consumed. The concentrations of algae and biomass also have gradually increased. In Group C and group D, algae concentration increase by12.6times and cell by26times. Net increases of biomass are33.9mg and36.68mg respectively, showing that the existence of Pseudomonas alcaligenes can increase the biomass of Characium.sp. Contrasting the algal cells concentration of the group C and group D, we find that group D is nearly63times of group C, but the differences of chlorophyll a content between both are small. And main difference between the two groups is that group D join the Pseudomonas alcaligenes, showing that bacteria cracking or secretions has certain effect on the synthesis of chlorophyll a. Finally, through the calculation of consumption of HCO3-, the experiment estimates the group C and group D has0.042mmol and0.0365mmol of HCO3-to return to the inorganic environment by the form of CaCO3. In group C,0.137mmol of HCO3-is absorbed by Characium.sp and preserves as organic carbon, accounting for23.3%of the total HCO3-. And in group D,0.175mmol is converted to organic carbon, accounting for29.7%.The results provide theoretical support to karst carbon effect, and at the same time provide new ideas for the future karst carbon study. |
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