Figure 3.

Relationships between the measured Sc uptake rate (J_Sc) and the calculated free Sc³⁺ concentration in the bulk water and in the phycosphere of freshwater algae under constant light (i.e., 100 μmol photons m^–2 s^–1). (a) The freshwater alga Chlamydomonas reinhardtii CPCC11 and (b) the freshwater alga Pseudokirchneriella subcapitata. The bulk medium pH⁵¹ was 5, and the phycosphere Sc³⁺ concentration was calculated by assuming a phycosphere pH 6 or 6.5. Both algae species were supplied with nitrate and ammonium, whereas the nitrate reductase-deficient C. reinhardtii CPCC11 cannot utilize nitrate. The solid lines correspond to the fittings by the Michaelis–Menten equation.