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Time to address threat of ocean acidification's impact on key members of ecosystem

Scientists' warnings about global climate change have been a hard sell in some quarters over the years because the consequences unfold over the course of decades, too slow to even seem tangible. For every ice sheet chunk that falls into the ocean, there's one weekend of really heavy snow to restore complacency.

The potential for damage to the oceans is a similarly abstract concept. The perils faced by marine ecosystems as temperatures rise are literally obscured from view under a blue facade. But a small legion of researchers, including several at Scripps Institution of Oceanography at the University of California, San Diego, are hoping to make these crises plain to even the most casual of observers.

A subtle problem only now being duly appreciated is ocean acidification. Vast increases in atmospheric carbon dioxide concentration in the past century have overwhelmed the natural systems that process the gas. When an extra helping of the gas is added to the oceanic mix, more combines with seawater to form carbonic acid.

This acid isn't nearly as strong as, say, hydrochloric acid, but its increasing presence has made oceans 30 percent more acidic than they were in pre-industrial times. Scientists know even seemingly minor fluxes of pH can have profound impacts on several species of organisms that make shells or skeletons out of calcium carbonate. More carbonic acid means less of the carbonate that corals, pteropods (relatives of garden snails) and other key ecosystem members need to form the structures they call home. Thus, creatures at the base of marine food webs and the world's largest biological structure, Australia's Great Barrier Reef, face a threat not just from ocean warming alone, but also from the chemical changes that accompany them.

It's hard to know at this point what the full extent of the consequences of increasing acidity in the oceans will be. It's possible damage will reverberate through ecosystems causing collapses of fish stocks we rely on for food. Needless to say, finding out what's happening won't get any easier unless we make an adequate attempt to understand what's happening. Scripps is calling for the establishment of a steady documentation of changes in ocean chemistry. This measurement series would be similar to the "Keeling Curve," the chart devised by Scripps's Charles David Keeling that has famously depicted the steady rise in global atmospheric carbon dioxide concentrations since the mid-20th century.

By now, no credible scientist disputes the evidence that people are changing climate to ends unknown. Few policymakers oppose taking prudent measures to address this potential threat. Now researchers and legislators need to task themselves with refocusing at least a portion of ocean chemistry research on this problem. In recent years, the Department of Energy ceased its monitoring of ocean carbon levels, arguing that the less comprehensive efforts of other federal agencies are adequate. In fact, they are not. We need an integrated and sustained observation program appropriate to the importance of this issue.

Monroe is editor of UCSD's Scripps Institution of Oceanography Explorations online magazine. Send comments to editor@sddt.com. All letters are forwarded to the author and may be used as Letters to the Editor.

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