Ocean acidification is not a result of climate change. Rather, like climate change, it is a result of increased carbon dioxide in the atmosphere. Combined with climate change, ocean acidification is affecting ocean ecosystems, the economy, and ultimately, our way of life.
The ocean naturally absorbs carbon dioxide due to a chemical reaction between the CO2 and H2O (the molecule that forms water). When CO2 and H2O react, they form a substance called carbonic acid. Carbonic acid is acidic; the more carbonic acid is in the ocean, the more acidic ocean water becomes. While some organisms live in a range of different pH levels and other organisms even thrive at a lower pH, still other organisms are directly affected by the lower pH and either cannot survive or suffer ill effects.
Furthermore, carbonic acid reacts with calcium carbonate. Calcium carbonate is the hard structure shell-building marine organisms use to make their shells. When combined with carbonic acid, these shells dissolve. Because the increase in carbonic acid in the ocean has been very small over time, the biggest effect has not been shells dissolving but in the decrease in calcium carbonate available in the water. The babies of shell-building marine organisms use free-floating calcium carbonate in the water to initially form their shells and add onto them; since some of the calcium carbonate has been dissolved by carbonic acid less calcium carbonate is available and babies struggle to form shells. Without the protection of shells, these organisms are eaten, washed away, or otherwise die, resulting in a smaller population of shell-building organisms.
We are already seeing the results of ocean acidification in the shellfish industry. Another important effect of ocean acidification is the fact that some microscopic photosynthetic organisms form shells. Photosynthetic organisms are important in the reduction of carbon dioxide in the atmosphere, because these organisms consume carbon dioxide in order to form their own food. As shell-building photosynthetic organisms die, carbon dioxide increases even more, contributing to the problem. Lastly, shell-building organisms are important to marine ecosystems, providing a diet for many animals in the ocean and animals who eat those animals and so on down the chain.
Ocean acidification can be a confusing term because while the ocean is acidifying, it is not becoming an acid. Ocean water is naturally basic; as a result of ocean acidification it is becoming a little less basic. Think about being in Antarctica; if you could increase the temperature by several degrees, we may use the word "warming" to describe the increase but we would not call Antarctica hot. The ocean will most likely never become an acid as a result of carbon dioxide, and we are unlikely to see drastic changes in marine ecosystems for some time. However, if carbon emissions continue as they have done, the long-term impacts of ocean acidification will be anywhere from significant to catastrophic.
