Since the Industrial Revolution a large amount of carbon dioxide (CO₂) as a result of human activities has been released into the atmosphere. Dissolution of CO₂ into seawater reduced the ocean pH and changed the balance of the ocean carbonate system. Ocean acidification threatens the marine ecosystems, especially calcifying organisms. Coccolithophore are major calcification plankton and play an important role in the ocean carbon cycle. Most of the culture experiments showed that the rise of CO₂ concentration would promote photosynthesis in coccolithophores. Ocean acidification has various effects on the calcification of different coccolithophore species or strains.