Fig. 6. A pH-[HCO₃^-] diagram for rainbow trout at 13°C. The P_CO2 for a given combination of pH and [HCO₃^-] was calculated using the Henderson-Hasselbalch equation and the appropriate values for pK' and the solubility coefficient CO₂ (Boutilier et al., 1984). The buffer line for rainbow trout true plasma was constructed using buffer values derived by Wood et al. (1982). The labelled points represent mean data (±1 s.e.m., N=8) for (1) pre-exposure, (2) pre-acetazolamide injection and (3) post-acetazolamide injection sampling points for trout exposed to hypercarbia (nominal PW_CO2 of 6 Torr; 1 Torr=133.3 Pa).