Greenhouse gases called threat to Pacific life

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SAN FRANCISCO -- The Pacific Coast is becoming saturated with carbon dioxide -- the major greenhouse gas -- making ocean waters more acidic and threatening a wide variety of marine organisms from Canada to Mexico, government scientists report.The world's oceans absorb millions of tons of the global warming gas each year, helping to slow the pace of climate change. But the benefit is far outweighed by extreme and damaging changes in the water's chemistry, according to seagoing oceanographers.In separate recent reports in the journal Science and in congressional testimony, the scientists warn that the rate of "ocean acidification" is increasing, and say damage to some of the most important living organisms in the sea's food web is becoming more apparent.The acid can endanger all kinds of marine animals, from the shells of microscopic plankton to the beaks of giant squid, biologists are finding from laboratory experiments and seagoing studies.Richard Feely, a chemical oceanographer in Seattle with the National Oceanic and Atmospheric Administration, estimates that the world's oceans have become at least 30 percent more acidic since the Industrial Age began more than 200 years ago. If greenhouse gas emissions continue uncontrolled, the world's oceans in this century will become 150 percent more acidic than they are today."While the changes are alarming, it's nearly impossible to predict how this unprecedented acidification will affect entire ecosystems," says Ken Caldeira, an atmospheric scientist with the Carnegie Institute's Department of Global Ecology at Stanford.Caldeira and his colleagues raise the issue in Science. Two weeks ago in the same journal, Feely's team reported on their most recent ocean survey along the West Coast and over the continental shelf. They were aboard NOAA's oceanographic research ship, Wecoma, sailing more than 2,000 miles from Queen Charlotte Sound in British Columbia to San Gregorio in Baja California.During May and June 2007, researchers on Wecoma took repeated samples of the upwelling water that rose from the deep sea bottom onto the continental shelf, where depths range from 120 to 1,200 feet. They discovered that the water had been heavily saturated with carbon dioxide and acidified as it lay on the bottom for 50 years.On another NOAA ship, the MacArthur II, water sampling by Feely's team revealed that the acidified water reached all the way to the surface, the scientists reported.Each spring along the West Coast, winds from the northwest blow strongly across the sea surface toward the shore and generate strong upwelling currents, Feely explained. The upwelling, in turn, brings water saturated with carbon dioxide from the deep bottom toward the surface. Then, as the gas mixes with seawater, it becomes carbonic acid, and when that acidity of the water becomes strong enough, it can dissolve the calcium carbonate shells of many of the sea's most important animals.Scientists have already reported the severe damage that acidity in seawater is causing to corals.But mussels, oysters, crabs, urchins, squid, and the kind of microscopic carbonate-shelled plankton that form the diet of creatures ranging in size from krill to whales are also organisms that can fall prey to increases in the ocean's acidity, Feely said.(E-mail David Perlman at dperlman(at)sfchronicle.com)(Distributed by Scripps Howard News Service, www.scrippsnews.com.)