Effect of Temperature on Inorganic Carbon Acquisition of Chlamydomonas reinhardtii

Carbon dioxide availability for microalgae in aquatic environments increases with decreasing water temperature, while photosynthetic activity generally decreases. Therefore, inorganic carbon acquisition by algal cells is greatly affected by temperature. We investigated half-saturation constants [Km(DIC), Km(CO 2 )] of inorganic carbon in photosynthesis under various temperatures for a strain of Chlamydomonas reinhadtii. C. reinhardtii showed an active carbon concentrating mechanism (CCM) at all temperature conditions investigated (5-25°C), implying that CCM activity is not diminished at low temperatures. The maximum photosynthetic rate was recorded at 15°C, while maximum CCM activity was detected at 20°C. A higher optimum temperature for CCM activity than for photosynthesis may compensate for lower photosynthetic rates above the optimum temperature. CCM may play a more significant role at higher temperatures in algal photosynthesis in aquatic environments.