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Ocean Acidification Worse than Thought

By Stephen Luntz

When it comes to carbon dioxide’s effects on the acidity of the oceans we need to fear extreme events rather than the average, a study published in Global Change Biology has warned.

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Carbon dioxide was once known as carbonic acid for its acidity when dissolved in water. Higher concentrations in the atmosphere increase the concentration in the upper oceans. This is causing what is known as ocean acidification, although technically the slightly alkaline oceans are becoming closer to neutral (AS, May 2008, pp.31–33).

Emily Shaw, a PhD student at the University of NSW Climate Change Research Centre, examined the natural variability in the pH of seawater around shallow reefs. “At the moment we have a lot of natural processes that cause variability,” says Shaw. “However, the ocean can buffer them. As we increase carbon dioxide levels in the atmosphere we reduce the ability of the ocean to absorb these changes.” As a consequence, not only will the oceans be more acidic on average, but extreme events will fall further from the mean.

Marine plants absorb carbon dioxide during the day but release some at night, changing the local acidity. Low tides produce greater swings in acidity as the effects of biological processes are distributed over a smaller volume of water than when the tides are high.

“In recognising that extreme changes in pH are likely in the future, it is important that further research is done to examine the biological consequences of short-term exposure to extreme carbon dioxide conditions,” says Shaw.

The concern is...

The full text of this article can be purchased from Informit.