Ocean acid levels rising with alarming speed

Posted: 1 December 2008

The planet's oceans are acidifying ten times faster than previously predicted according to new research, Don Hinrichsen reports.

Reporting on the result of an eight-year project carried out in the Pacific Ocean, off the coast of Washington State, scientists at the University of Chicago, have found that rising acid levels in surface waters was impeding the ability of calcifying organisms, such as mussels, clams, oysters, coral polyps and crustaceans, to produce the calcium needed to generate their shells.In the case of coral polyps, it is making it more difficult for them to build reefs. These processes are critically dependent on a more alkaline environment.

The bleached staghorn coral turns white and is starving without its symbiotic algae. Photo: Justin Marshall.
The bleached staghorn coral turns white and is starving without its symbiotic algae. Photo: Justin Marshall.
The bleached staghorn coral turns white and is starving without its symbiotic algae.© Justin Marshall
Timothy Wootton, one of the primary scientists involved in the study, said their findings indicated that acidity levels in the ocean were ten times greater than those predicted by the best computer models available.

According to Professor Wootton: "An alarming surprise is how rapidly pH has declined over the study period ... These data point to the urgency of obtaining a globally extensive set of ocean pH data through time, and suggest that our understanding of ocean pH may be incomplete.

"The results showed that variation on ocean pH through time was most strongly associated with increasing atmospheric carbon dioxide, which supports the prediction that increasing release of CO2 to the atmosphere leads to ocean acidification," he concluded.

Ocean sink

Atmospheric carbon dioxide has increased by 100 parts per million since the start of the industrial revolution and they are now at the highest levels in over half a million years.

The world ocean acts as a sink for about one third of all carbon dioxide emissions for which humans arew responsible. As the carbon dissolves in the ocean it forms carbonic acid, which lowers sea water's alkalinity and pH level, making it more acidic.

In 2007, the Intergovernmental Panel on Climate Change (IPCC) predicted that most coral reefs could disappear by the end of this century - victims of rising water temperatures and ocean acidity.

Don Hinrichsen is a Contributing Editor of this website and author of Coastal Waters of the World, Island Press, Washington DC, $60 hb.