Climate Fact: Formaniferans, Ocean Acid and Carbon Concentrations
When carbon dioxide (CO2) enters the ocean, it bonds with water to create carbonic acid, releasing an extra proton in the process. The extra proton bonds to a carbonate molecule in the water, creating more carbonic acid and leaving fewer carbonate molecules for creatures like coral and foraminiferans (a group of single celled, primarily marine organisms) to use to build skeletons. The oceans are currently absorbing about 22 million tons of CO2 each day and have absorbed an estimated 525 billion tons of CO2 over the last 200 years. As a result, over this same period, the oceans have become more acidic. On the pH acidity scale (which ranges from 0 to 14, with 0 being the most acidic and 7 being neutral) the world’s oceans have fallen from a pH of 8.2 in the late 18th century to a pH of 8.1 today, a 30 percent increase in acidity. One result of this process has been a thinning of foraminiferan shells. Because these tiny organisms build their bodies out of carbonate, they have been forced to adapt by surviving with thinner shells. Sediment cores from the Southern Ocean indicate that foraminiferan shells are one-third thinner than they were in pre-industrial times.
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Sources: Hoegh-Guldberg et al. “Coral Reefs Under Rapid Climate Change and Ocean Acidification.” Science 318 (2007): 1737 and “Oceans Becoming More Acidic, Potentially Threatening Marine Life.” Science Daily 23 February 2009. Accessed Online 25 February 2009
