Ocean acidification

Carla Edworthy tells us about the threat to the world’s marine environment, and research advances in South Africa

It is now widely accepted that ever-increasing emissions of carbon dioxide (CO2) from fossil-fuel burning and other human activities are causing global climate change. Some of the better-known consequences for our oceans are increasing temperatures, sea level rise and more frequent or intense storm events. But by continuously releasing CO2 into the atmosphere, humans are significantly altering the chemistry of the oceans too. Although it is not as widely known, ocean acidification is considered the ‘evil twin’ of global climate change.

The oceans act as a giant sink for carbon because CO2 dissolves rapidly in seawater, initiating a succession of chemical reactions. The ultimate result of these reactions is a decline in the pH of seawater. Although the global average pH is currently about 8.1, this is slowly decreasing as CO2 continues to be absorbed by the oceans from the atmosphere. By the end of the century, the global average pH is predicted to fall to approximately 7.7 if global CO2 emissions continue unabated, which is considered a worst case scenario. Since pH is measured on a log scale, a drop in pH of one unit actually represents a tenfold decrease in acidity. This means that even a small change in pH significantly changes the acidity of seawater.

SAIAB, 12 July 2021. Article.

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