Figure 4.

The effect of external C_i on C_int/C_ext at pH 7.0 (A) and 8.0 (B) for Symbiodinium sp. freshly isolated from T. gigas. Passive diffusion indicates the C_int/C_ext expected if only passive diffusion of CO₂ into the cell was occurring, assuming an intracellular pH of 7.62. Assays were conducted using silicone oil centrifugation in 25 mm BTP and 428 mm NaCl at a photon flux density of 500 μE m⁻² s⁻¹ using H¹⁴CO₃⁻ as a substrate as in “Materials and Methods.” Error bars represent ses (n = 3).