The pH of a solution is a measure of how acidic or basic it is. The greater the pH, the more basic the solution is. Corals and other marine invertebrates require less energy to make their exoskeletons and shells when ocean water is slightly basic. As carbon dioxide concentrations in Earth’s atmosphere rise, ocean water absorbs carbon dioxide and becomes more acidic. This process is called ocean acidification. How do you think ocean acidification will affect the coral reef?