How would increasing carbon dioxide levels in the atmosphere affect the ocean plankton? [Pg. No. 252]

Increasing carbon dioxide levels in the atmosphere affect ocean plankton mainly through ocean acidification. When CO₂ dissolves in seawater, it forms carbonic acid, which lowers the pH of the ocean. This makes it difficult for shell-forming plankton, such as some phytoplankton and zooplankton with calcium carbonate shells, to build and maintain their shells. Some phytoplankton may use extra CO₂ for photosynthesis, but their growth also depends on sunlight, nutrients and temperature. If plankton populations decline or their balance changes, it can disturb the marine food chain because plankton form the base of many ocean ecosystems and support fish and other marine organisms.