Ecophysiology matters: linking inorganic carbon acquisition to ecological preference in four species of microalgae (Chlorophyceae)

The effect of CO 2 supply is likely to play an important role in algal ecology. Since inorganic carbon (C i ) acquisition strategies are very diverse among microalgae and C i availability varies greatly within and among habitats, we hypothesized that C i acquisition depends on the pH of their preferred natural environment (adaptation) and that the efficiency of C i uptake is affected by CO 2 availability (acclimation). To test this, four species of green algae originating from different habitats were studied. The pH‐drift and C i uptake kinetic experiments were used to characterize C i acquisition strategies and their ability to acclimate to high and low CO 2 conditions and high and low pH was evaluated. Results from pH drift experiments revealed that the acidophile and acidotolerant Chlamydomonas species were mainly restricted to CO 2 , whereas the two neutrophiles were efficient bicarbonate users. CO 2 compensation points in low CO 2 ‐acclimated cultures ranged between 0.6 and 1.4 μM CO 2 and acclimation to different culture pH and CO 2 conditions suggested that CO 2 concentrating mechanisms were present in most species. High CO 2 acclimated cultures adapted rapidly to low CO 2 condition during pH‐drifts. C i uptake kinetics at different pH values showed that the affinity for C i was largely influenced by external pH, being highest under conditions where CO 2 dominated the C i pool. In conclusion, C i acquisition was highly variable among four species of green algae and linked to growth pH preference, suggesting that there is a connection between C i acquisition and ecological distribution.