Increased carbon dioxide (CO2) in the atmosphere eventually makes its way into the ocean. As this CO2 is absorbed, the pH of the ocean drops, resulting in a more acidic environment. Normal seawater is between 7.5 and 8.5 pH and anything below 7 is considered acidic. Corals use calcium carbonate to build their solid skeletons, but in an acidic ocean, this skeleton becomes weaker and corals have more difficulty building their skeleton. While this is not such a concern for mature colonies, ocean acidification may be affecting the growth and development rates of baby corals, causing deformities in their skeletons.