The ocean is absorbing large amounts of carbon dioxide—a natural process. However, as carbon dioxide enters the ocean, it reacts with water to form acid. Subsequent chemical reactions that try to maintain a normal pH level in the ocean end up reducing the amount of calcium carbonate—a component in the skeletons of many organisms such as corals, lobsters, clams, and pteropods. Without calcium carbonate, these organisms cannot properly grown and reproduce. In this animation, we show model data of how the availability of calcium carbonate is predicted to decrease over the next century at a depth of 10 meters in the ocean—where most corals occur. Areas that are deep red are sufficiently acidic to dissolve calcium carbonate-based organisms. Most areas currently have enough calcium carbonate to support corals and other organisms, but all areas are predicted to decline by the year 2100 compared to pre-industrial values.