Acid Oceans: A New Twist To Report When Covering Climate Change

February 15, 2005


The increasing levels of carbon dioxide in the atmosphere due to human activities, such as burning fossil fuels and deforestation, is well known. Scientists – with the exception of some skeptics – predict changes in the Earth's climate from rising levels of carbon dioxide and other greenhouse gases.

But rising concentrations of carbon dioxide in the atmosphere are also turning the oceans sour, according to recent scientific reports. This can endanger sea creatures such as clams and coral by weakening shells or exoskeletons. This, in turn, could have major impacts on marine species that feed on shellfish or depend on coral ecosystems.

Commercial fisheries could also be affected, and the protection that coral reefs provide from tsunamis would likely be diminished.

Scientists estimate that the world's oceans have already absorbed about half of the carbon dioxide released by human activities over the past 200 years, since the Industrial Revolution. The pH of the oceans has fallen during that time.

Understanding how carbon dioxide in the atmosphere relates to ocean mollusks and corals requires a little basic chemistry.

The pH scale ranges from 0 to 14, with 7 as neutral. ApH less than 7 is acidic, while a pH greater than 7 is alkaline, or basic.

Surface waters of the world's oceans now have a pH that averages about 8.08, according to Britain's Royal Society. Sea water has already gotten a bit less alkaline due to emissions of carbon dioxide. Two-hundred years ago, the oceans' pH was about 0.1 higher, scientists estimate.

What happens chemically in the ocean when sea water absorbs carbon dioxide is the same process that helps make Coke and Pepsi acidic. (Soda pop, which usually includes citric or phosphoric acid, has a pH of about 3.)

In this process of carbonation, carbon dioxide and water react to form carbonic acid. But oceans differ from the sugary water that soft drink makers bubble carbon dioxide into.

Sea water is what chemists call a buffered solution. This means it has the ability to absorb carbon dioxide and, though its pH drops somewhat, still remain alkaline.

Carbonate ions found in sea water are responsible for this buffering action. (Chemistry detail – the carbonate reacts with the hydrogen in carbonic acid to form bicarbonate.) However, the buffering capacity of the oceans will decrease as their waters take in more carbon dioxide from the atmosphere and carbonate levels decline.

The effects of increased ocean acidity could be wide ranging, with the most severe effects expected in the Southern Hemisphere.

Shellfish, such as oysters and scallops, as well as coral reefs, sea urchins, and starfish are likely to find it difficult to develop and maintain their shells and exoskeletons, which are made of calcium carbonate. This is because calcium carbonate, the same stuff chalk is composed of, will dissolve in sea water unless that water contains a high concentration of carbonate . Some types of plankton, a key part of the oceanic food web, have shells made of calcium carbonate and they may be adversely affected too.

Projections are that by 2100, surface waters of the oceans will experience a pH drop of up to 0.5. That's a sharp drop over a short time, scientists point out, and would be the least alkaline the oceans have been in hundreds of thousands of years or longer.

Journalists who wish to explore this subject further can find more information through the following links:

• The Royal Society (U.K.) 2005 report at: • NOAA article and link to workshop highlights: • pH comparisons of familiar liquids on page 4 of this document:

Cheryl Hogue reports for Chemical & Engineering News.

**From SEJ's quarterly newsletter SEJournal Winter, 2005 issue

Environmental Journalism Fellowship At Kauai Gardens


The National Tropical Botanical Garden annual Environmental Journalism Fellowship program will take place May 8-13, 2006 on the Hawaiian island of Kaua'i. Application deadline is Feb. 27, and acceptance notification on March 8.


NTBG's fellowship provides working journalists in broadcast, print or online media information about ethnobotany and tropical ecosystems. The week-long, intensive course provides deep background in tropical ecology with daily field trips supervised by NTBG's research scientists. Study areas include historic, ancient Hawaiian cultural sites and botanical collections extending back to the period of Hawaiian royalty in the late 1800s.

The congressionally authorized, nonprofit organization offers a rich living classroom for basic concepts in tropical biology, indigenous use of plants for medicine and the ecology of tropical fauna. The Garden is a nesting site for both threatened Green sea turtles and endangered water birds.

Lodging, airport transfer, ground transportation, and meals are provided. Journalists are responsible for their own airfare to and from Lihu`e, Kaua`i, Hawaii. Application information is available at

Requests about the NTBG Environmental Journalism Fellowship may be directed to Dr. Gaugau Tavana, Director of Education, National Tropical Botanical Garden, 3530 Papalina Road, Kalaheo, HI 96741.Telephone: (808) 332-7324 ext. 225 or 251. Fax: (808) 332-9765, Or contact Dr. JoAnn M. Valenti, course coordinator, at, (801) 942-8516.