Experimental study on the utilization of DIC by Oocystis solitaria Wittr and its influence on the precipitation of calcium carbonate in karst and non-karst waters

The difference in dissolved inorganic carbon (DIC) utilization and calcium carbonate precipitation by Oocystis solitaria Wittr grown in closed systems of karst water and non-karst water was investigated by using a free pH-drift experiment. It was found that the HCO 3 − as carbon resource of Oocystis solitaria Wittr photosynthesis was catalyzed by carbonic anhydrase to CO 2 at low CO 2 concentration. The DIC utilization and induced calcium carbonate precipitation by Oocystis solitaria Wittr were much higher (4.6 and 10-fold, respectively) in karst water than in non-karst water. In karst waters, 42.6% of decreased calcium ions were precipitated as calcium carbonate; in non-karst waters, 8.9% were precipitated via physiochemical effect and the remaining were utilized by Oocystis solitaria Wittr for its growth. These findings clearly show the greater importance of karst water environment in DIC fertilization effect on the growth of Oocystis solitaria Wittr due to its higher concentrations of DIC, which is significant to the karst process-related carbon sink.