Ask Vanessa: Our acidic oceans

Dear Vanessa,

I’m trying to learn more about climate change and have been reading as much as I can. I keep coming across terms I don’t understand, like ocean acidification. What is ocean acidification, and why does it matter?

– A curious reader

Dear Curious,

By now, most folks know that carbon dioxide-induced global warming is causing changes in ocean temperatures and precipitating a rise in sea levels. Still off the radar for many, though, is that carbon dioxide emissions are making the ocean more acidic. When carbon dioxide (CO2) is absorbed by seawater, carbonic acid is formed, reducing the water’s pH level and the concentration of carbonate ion. This process is commonly called ocean acidification. Perhaps surprisingly, ocean acidification is considered one of the most serious consequences of increased CO2 in the atmosphere.

It is estimated that the ocean has absorbed more than 528 billion tons of CO2 from the atmosphere – about one-third of human-caused carbon emissions – since the beginning of the industrial revolution.

On the one hand, the ocean’s absorption of CO2 helps reduce the amount of greenhouse gases in the atmosphere – a positive, useful function in these dire times. On the other hand, the ocean’s absorption of CO2 and the ensuing drop in seawater pH level has widespread and devastating effects on marine and human life. The lower pH level inhibits the ability of many marine plants and animals to build their shells and skeletal structure, in some cases even dissolving the shells. Ocean acidification is particularly harmful to surface and deep-water corals, plankton, snails, lobsters, clams, oysters and other mollusks.

Beyond individual organisms, ocean acidification holds broad repercussions for entire ecosystems – and human survival. The plant and animal organisms most affected by ocean acidification provide critical habitat and food sources for other organisms. Simply put, if life “lower” on the food chain dies, eventually we do, too. Ocean acidification exacerbates problems already faced by fisheries and marine ecosystems, including over-fishing, pollution, excess nutrients, invasive species and habitat destruction.

Carbon emissions from human activity have led to a 30 percent increase in the acidity of ocean surface waters. Scientists and researchers estimate that seawater pH will drop rapidly to 7.7 from a normal 8.1. In June, 70 of the world’s science academies came together in Bonn, Germany, to warn of dire consequences for food production and the livelihoods of millions if the issue of ocean acidification is not addressed. Their joint statement asserts that oceans are more acidic now than they have been for 800,000 years.

“The effects will be seen worldwide, threatening food security, reducing coastal protection and damaging the local economies that may be least able to tolerate it,” said Martin Rees, president of the Royal Society, the national academy of science of the U.K. and the Commonwealth.

In short, ocean acidification is a result of excessive, human-generated CO2 emissions. Through basic chemical reactions, the atmospheric CO2 emissions absorbed by seawater lead to a drop in the oceans’ pH balance, in turn causing one of the most significant impacts of rising CO2 levels.

As usual, we have the capacity to change this destructive course. The question remains whether we will choose to do so, and do so quickly enough.

Keep it Green,


Mother Nature Network (, The Miami Herald, 27 July 2009. Article.

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