Here we investigate how CO₂ enrichment affects the relationships light–production and light–calcification in coral reef communities. For the three communities tested, CO₂ did not affect the light–production relationships, while calcification was lower at elevated CO₂ for all light levels. Our result indicates that CO₂ can modify the balance between net calcification and net photosynthesis of reef communities by depressing community calcification without affecting community photosynthesis.