Ocean acidification

"Ocean acidification (OA) is the process of declining pH in seawater that results from the ocean’s absorption of anthropogenic carbon dioxide (CO2) from the atmosphere. The average pH of the surface ocean has already declined by 0.1 of a pH unit to 8.1 since the beginning of the industrial revolution and is predicted to decline by another 0.2 to 0.4 units by 2100. The carbonate ion concentration has also declined by more than 10% during this period. The carbonate concentration in seawater is the prime determiner of whether biogenic calcium carbonate either precipitates or dissolves; hence, concern is growing for those organisms with shells of calcium carbonate, particularly those made of aragonite that dissolves more readily than calcite."