Marine acidification will be an important environmental problem in the near future as a result of persistent emissions of CO₂ and dissolution into seawater. In this study, we found that calcification and respiration of the Zhikong scallop (Chlamys farreri) are likely to be severely affected by increasing acidification. Calcification and respiration significantly declined as pH decreased. The calcification rate decreased by 33% when the pH of water was 7.9 compared with a pH of 8.1, and decreased close to 0 when the pH was reduced to 7.3. CO₂ and O₂ respiratory rates were reduced by 14% and 11%, respectively, when pH decreased from 7.9 to 7.3. Increasing acidification also led to changes in the metabolic pathways of C. farreri. Under acidic conditions, proteins may replace carbohydrates as the metabolic substrate. The survival of C. farreri is likely to be severely threatened in the next few centuries.