Climate change is not the only outcome of increased greenhouse gas concentrations. The oceans have absorbed a lot of the excess carbon in the atmosphere, reducing the impacts of climate change to date, but at a cost. Higher concentrations of carbon dioxide (CO2) in the atmosphere have led to an increase in acidity of ocean water, a process known as ocean acidification. The process of acidification is laid out by Cheryl Logan in a user-friendly 2010 summary in the journal Bioscience.

Ocean acidification occurs when CO2 dissolves in ocean water, undergoing a chemical reaction that produces carbonic acid. The rate of this reaction is completely predictable and as a result the progression of acidification as CO2 levels increase is completely predictable. Unlike climate change, ocean acidification is not controversial at all—basically nobody disputes that it is happening—and happening rapidly.

As Logan explains, acidity is measured through the concentration of hydrogen ions—called the pH scale, for power of hydrogen—more hydrogen equals greater acidity. Since the late 19th century, the concentration of hydrogen ions in the ocean has increased by 30%, and that will increase another 150% by 2100, according to common emissions projections.

That is a massive change to ocean chemistry in a short amount of time, and many of the ocean’s inhabitants are struggling to adapt. The shells of many marine organisms are made of calcium carbonate, which is highly susceptible to acid. Logan explains how some organisms are starting to have trouble forming new shells, and in extreme cases, existing shells are getting thinner.

Just in case the plight of a few snails seems like a relatively minor concern, the issue goes well beyond snails. Corals, sea urchins, many species of plankton- organisms crucial to marine habitats and food webs- all rely on calcium carbonate as part of their structure. Some research even suggests that acidification can disrupt the ability of plants to perform photosynthesis. As marine organisms are responsible for much of the Earth’s oxygen production, this might one day threaten our very survival.

Acidification has the potential to completely disrupt the ocean’s—and perhaps even the planet’s—ecosystem before climate change has a chance to do so. Despite the urgency Logan describes, the American public is largely unaware of the issue. Public awareness notwithstanding, the solution to ocean acidification is straightforward: burn less carbon. Efforts to curb the climate change will address acidification as well, but progress is slow. It is astounding that such a key issue, one that might genuinely threaten our survival as a species, is still so little-known.




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Bioscience, Vol. 60, No. 10 (November 2010), pp. 819-828
Oxford University Press
Environmental Health Perspectives, Vol. 118, No. 4 (APRIL 2010), p. A157
The National Institute of Environmental Health Sciences (NIEHS)