Almost half the carbon dioxide from the past two centuries of industry has been absorbed by the world's oceans, researchers say, causing changes in ocean chemistry that pose a long-term risk to corals and shell-forming marine life. The findings suggest that burning fossil fuels such as coal and oil could have ecological consequences by the end of the century that go beyond the present concern with carbon dioxide as a greenhouse gas that can contribute to global warming. The research was published this week in the journal Science. Oceanographer Christopher Sabine, of the National Oceanic and Atmospheric Administration in Seattle, and his colleagues found that oceans absorbed 48 per cent of the carbon dioxide emissions from fossil fuel burning and cement manufacturing between 1800 and 1994, or about 118 billion metric tonnes of carbon. Dr Sabine said the oceans still had the capacity to take up carbon dioxide "for thousands of years". But the impact on marine life could be felt much quicker. A companion study, led by the Atmospheric Administration marine chemist Richard Feely, of the Pacific Marine Environmental Laboratory in Seattle, says the dissolution of acidic carbon dioxide in ocean surface waters can decrease their alkalinity. If, as some computer models suggest, the concentration of carbon dioxide in the atmosphere increases to as much as 800 parts per million by century's end - up from about 380 parts per million now - the authors say corresponding changes in seawater chemistry "can potentially have significant impacts on the biological systems in the oceans in ways we are only beginning to understand". Of primary concern are the many molluscs, corals and single-celled creatures that use ingredients in seawater to build their shells and other hard parts. They pull carbonate ions out of the water and make a hard material called calcium carbonate or limestone. As the concentration of carbon dioxide increases in seawater, the carbonate ion concentrations decrease. At depths where the ion levels fall too low, the calcium carbonate shells are likely to start to dissolve and the creatures die. By Earl Lane in Washington Newsday, The Boston Globe Source : www.smh.com.au
