I invite you to find the answer to your question by looking the attached paper.

It doesn't have to be adapted to high CO2 concentration. Rather, it can be adapted to this level in order to present a specific phenotype.

Algae, which are cultivated in water are exposed to HCO3-[aq] as the main form of carbonic acid which is dissolved in water at pH 7.5-8.4 (most earth water body pH).  This is unfortunate  because the algae can use only CO2 when it comes to biomass production - RUBISCO can fixate CO2 or O2 only.

Therefore, it developed a Carbon Concentrating Mechanism - CCM - (-  CO2 concentrating mechanisms in photosynthetic microorganisms‏ - Kaplan A 1999) , to reach the following: 1. insert alot of inorganic carbon into their cells and 2. make RUBISCO fix CO2 rather than O2.

The CO2 concentration in the medium affects the plasticity of this mechanism -see this great review by  Natalia Batchikova - http://www.sciencedirect.com.rproxy.tau.ac.il/science/article/pii/S0005272810007255

Hope that helps,

I am not sure what you exactly mean.

Anyway, yes, algae can acclimate and adapt to elevated CO2, in different ways and to different extent.

I am also attaching a few more papers that hopefully can help you.

You can also look at the work by Sinead Collins on long term culture at high CO2. If you are thinking of biomass production or alike, look at 

"M Giordano, S Ratti - Journal of Applied Phycology, 2013. The biomass quality of algae used for CO2 sequestration is highly species-specific and may vary over time"

Dearest Professor

Hi, thank you for your time and efforts.

Obviously, the question was that why micro algae cells should be adapted to CO2 to capture CO2 in high concentration as CO2 is not known as a toxic gas. and also why there is no proper removal efficiency for CO2 in high concentration like 25% CO2?

thanks

At 25% CO2 mix with air  the algae deal with extreme medium acidification. This field is beyond my area of expertise but if I had to throw an educational guess i'd say that at such acidic conditions the algae will invest enormous amount of energy to keep homeostasis ( which will probably kills them... making CO2 toxic eventually) and so the CO2 removal pathway will be secondary to any effort to stabilize their internal pH.

A supreme reference for carbonic acid kinetics in water is Wolf-gladrow book : CO2 in sea water- a good friend along this way.

Hope this information helped, 

Dearest Professor

sorry to bother you over again. as you know scientific researches demonstrated that during CO2 fixation the water PH dramatically increase to 7-10 cause calcite deposition, therefore, as you mentioned, whether decreasing in water PH occur before CO2 fixation process? and also advise me to solve this problem. 

thanks