Fig. 7. CO₂ uptake rates (µmol g^-1 h^-1) as a function of O₂ uptake (µmol g^-1 h^-1) and H₂S uptake rates (µmol g^-1 h^-1) by Riftia pachyptila. Four Riftia pachyptila were placed in high-pressure aquaria, maintained until autotrophy, then O₂ and H₂S concentrations were alternately increased from 27 to 130 µmol l^-1 and 0 to 140 µmol l^-1, respectively. All other substrates were held at `typical' in situ concentrations (see Materials and methods). All rates are expressed in terms of wet mass. Env., environmental.