Simulation Study On The Influence Of Environmental Factors And Carbonic Anhydrase On Carbon Stabilization Ability Of Microalgae From Karst Area

Microalgae play an important role in carbon fixationin aquatic ecosystem.Carbonic anhydrase?CA?plays an important role in CO₂-concentration mechanism?CCM?.However,at present,the studies on carbon stabilization abilityof microalgae utilizing dissolved inorganic carbon?DIC?in karstwaters and converting DICinto organic carbon,as well asthe influence of environmental factors and CA on carbon stabilization abilityof aquatic microalgae,are less reported.In this study,an air-lift device for algae cultivation was designed.Chlorella and Scenedesmus,which were screened and isolated from karst waters,were used as the research object,and werecultivated in the artificial karstwaters.The influence of different illumination intensityand HCO₃^-concentration on DIC sequestration capacityof microalgae on the conditions of CA addition and CA inhibited was explored.In addition,the sediments formed during the cultivation processof microalgae werefurther collected,and the degradation experiments ofsediments were carried out.The degradation extent of sediments produced in different environmental conditions was investigated.The main results obtained in this paper are as follows.?1?With the increasing of illumination intensity and HCO₃^-concentration,the biomass and sedimentsproduced of microalgaeincreased significantly?P<0.01?.Moreover,when the HCO₃^-concentration was higher,the growth rate of biomass and sediment amountin CA enhanced groups and control groupswere higher than those of CA inhibited groups.Above resultsshowed that on the condition of higher HCO₃^-concentration and higher illumination intensity,the microalgae could utilize more inorganic carbon under the action of CA.?2?The existence of inorganic carbon was detected in the sedimentsformed in the cultivation process of microalgae.InChlorellacultivation process,there existed a positive correlation between the decreasing amount of Ca²⁺concentration and average biomass during stable phase?R²=0.41,P<0.01?.Theseresults suggested that the utilization of HCO₃^-by microalgae mightpromote the deposition of Ca²⁺in karst waters.The organic matter in sediments was degraded rapidly in 12 d,and after 48d,the degradation rateremained between 63.29%and 97.22%,which showedthat a certain amount of refractory organic matter might form after inorganic carbon used by microalgae was converted into organic carbon.Moreover,on the condition ofhigh HCO₃^-concentration and high illumination intensity,more refractory organic matter would produce in microalgae cultivation process,which possessedstrongercarbon stabilization ability.The results revealed the influence of illumination intensity,HCO₃^-concentration andCA on carbon stabilization ability of aquatic microalgae in karst area,which provide the theoretical basis for scientific understanding of the role of microalgae and their CA inincrement of carbon sinkin karst ecosystems.