In this study, the effect of pH values ranging from 5.5 to 6.5, ad- justed by the addition of various amounts of CO2 on two species of blue-green algae during different growth stages, were investigated. The purpose of this study was to evaluate the effects of the CO2 acidification method on the control and management of summer blooms caused by blue-green algae. To the best of our knowledge, this is the first study to use carbon dioxide to regulate the pH of the culture medium to inhibit the growth of blue-green algae. In addi- tion, CO2 is recognized as the main gas causing global warming; however, our study can be used to identify methods of decreasing the CO2 concentration in the atmosphere and thus reducing the problem of global warming to a certain extent. Accordingly, the re- sults presented herein will help manage summer blooms of surface water and decrease greenhouse gas emissions.