Oceans absorb roughly 25% to 30% of the carbon dioxide (CO2) that is released into the atmosphere. When this CO2 dissolves in seawater, it forms carbonic acid, making the water more acidic and altering its chemistry. Elevated levels of acidity are harmful to marine life like corals, oysters, and cer tain plankton that rely on calcium carbonate to build shells and skeletons. ...read more read less