Effects of CO2 concentration gradient on carbonic anhydrase of two karst microalgae

In response to the challenge of global warming,it is important to study karst microalgae and its carbonic anhydrase for greenhouse effect owing to carbon sequestration.Yaji experimental site is an independent karst hydrological-geological system located in the peak-cluster depression and the peak-forest plain border zone.The experiment was conducted on the Chlorella vulgaris and Nostoc calcicola Breb.cultured on the spring water which sources from the limestone of Rongxian formation,the upper Devonian at the site.We compared the carbonic anhydrase activities of two different microalgae under different carbon dioxide concentrations by using the methods of Willbur and Anderson in a closed system and analyzed the changes of karst factor by using the WTW350i multifunctional water quality analyzer and the hardness and alkalinity kits.The results showed that the karst micro-algae could deal with the habitat impact of elevated carbon dioxide by rapidly regulating its carbonic anhydrase activity in the environment of less than 3 % carbon dioxide concentration.The activities of carbonic anhydrase in Chlorella vulgaris was increased by 1.46 times and Nostoc calcicola Breb.was increased by 2.12 times respectively in the environment of 2.5 %.The increase of carbon dioxide concentration leads to the change of karst factor,resulting in the decrease of pH,HCO3 and dissolved oxygen (DO) and the increase of electrical conductivity (EC).Karst microalgae play an important role in coping with the decrease of pH and HCO3-induced by the increase of carbon dioxide concentration.With the increase of incubation time,the pH and the HCO3-in the culture environment is recovered,indicating that the karst area is an important participant in response to global warming.With the increase of carbon dioxide concentration,karst factors have an important influence on carbonic anhydrase.The correlation between calcium ion of Nostoc calcicola Breb.and carbonic anhydrase was the highest at 48 h,but the correlation between EC and carbonic anhydrase of (Chlorella vulgaris) reached it highest at 48 h.Due to the correlation between carbonic anhydrase and calcium ion,the influence of calcium ion can not be neglected when we study the relationship between carbonic anhydrase and karst dynamics in karst area.