A usage of CO sub(2) hydrate: Convenient method to increase CO sub(2) concentration in culturing algae

The addition of CO sub(2) to algal culture systems can increase algal biomass effectively. Generally, gas bubbling is used to increase CO sub(2) levels in culture systems; however, it is difficult to quantitatively operate to control the concentration using this method. In this study, we tested the usability of CO sub(2) hydrate for phytoplankton culture. Specifically, green algae Pseudokirchneriella subcapitata were cultured in COMBO medium that contained dissolved CO sub(2) hydrate, after which its effects were evaluated. The experiment was conducted according to a general bioassay procedure (OECD TG201). CO sub(2) promoted algae growth effectively (about 2-fold relative to the control), and the decrease in pH due to dissolution of the CO sub(2) in water recovered soon because of photosynthesis. Since the CO sub(2) hydrate method can control a CO sub(2) concentration easily and quantitatively, it is expected to be useful in future applications.