An alert on ocean acidity

Carbon dioxide emissions from man-made sources are causing the acidity level of the world’s oceans to rise at what is probably the fastest rate in 65 million years, threatening global fisheries that serve as an essential food source for billions of people, according to a new United Nations report.

Roughly 25 percent of the carbon dioxide generated by the combustion of fossil fuels enters the oceans, and as the gas dissolves in seawater it changes into carbonic acid. One result has been a rapid alteration in ocean chemistry that is already affecting marine organisms.

The acidity of the oceans has grown 30 percent since the beginning of the Industrial Revolution. At current emission rates, ocean acidity could be 150 percent higher by the end of the century, the report states.

Marine life and coral reefs have already shown vulnerability to rising levels of acidity, and the changes expected in coming decades are severe enough that they could have a serious impact on the ability of people around the world to harvest needed protein from the seas, according to Carol Turley, senior scientist at Britain’s National Oceanography Center and the lead author of the report.

“We need to start thinking about the risk to food security,” Dr. Turley said in a statement.

The report also warns that the rise in ocean acidity poses a severe threat to coral reefs, which are already under stress from pollution and the warming of oceans — a concern shared by a growing number of marine scientists.

Acidification could conceivably wipe out most of the world’s already ailing coral reefs within a generation or two, said John Veron, former chief scientist of the Australian Institute of Marine Science, in an essay posted this week on the Web site Yale Environment 360.

“The potential consequences of such acidification are nothing less than catastrophic,” Dr. Veron wrote.

As acidification continues, coral and marine organisms like shellfish will begin to suffer from osteoporosis — an inability to fix calcium into shells and other structures.

“No doubt different species of coral, coralline algae, plankton and mollusks will show different tolerances, and their capacity to calcify will decline at different rates,” Dr. Veron wrote. “But as acidification progresses, they will all suffer from some form of coralline osteoporosis.”

“The result will be that corals will no longer be able to build reefs or maintain them against the forces of erosion,” the article continues. “What were once thriving coral gardens that supported the greatest biodiversity of the marine realm will become red-black bacterial slime, and they will stay that way.”

John Collins Rudolf, New York Times Green blog, 8 December 2010. Article.

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