Ocean Acidification

Chemists first theorized the process commonly referred to as “ocean acidification” in the 1970s, but only during the past few years have researchers begun to fully appreciate the threats it poses to ocean inhabitants such as corals and fish.

With few major studies yet completed, researchers over the past few years have been encouraging the U.S. to launch a coordinated ocean acidification research program. Authorized in March but not yet funded, the program’s overarching goal will be to decipher ocean acidification’s biological and economic impacts to enable informed and adequate response to the issue.

Ocean acidification is not a climate change per se, but rather a separate, though closely linked, problem. The oceans naturally absorb huge quantities of carbon dioxide, a weak acid, from the atmosphere, which sets off a string of chemical reactions in seawater. This reaction includes conversion of calcium carbonate, which helps control pH levels and is used by many animals to build their shells into a form that is biologically unusable.

Oceans 30 Percent More Acidic than in 1750

So, more carbon dioxide in the atmosphere means more dissolving in the ocean, causing calcium carbonate concentrations to drop, along with pH. Hence, the name ocean acidification, though the oceans are actually still basic, with a pH above 8. (Journalists and other communicators educating lay audiences on important ocean acidification issues should make sure their audiences understand that the waters are indeed basic and not actually acidic.)

Monitoring shows that the oceans have already become 30 percent more acidic since 1750, a problem that Energy Secretary Steven Chu recently testified might eventually put the entire ocean food chain at risk.

In limited experiments, lower pH causes problems such as slowed coral reef building, establishing a threshold beyond which reefs actually dissolve more quickly than corals can build them. This condition doesn’t mean a reef is “dead,” but as Joanie Kleypas, a prominent acidification researcher from the National Center for Atmospheric Research in Boulder, Co., puts it, “That’s not the side of the line we want to be on.” Another concern is that the process may generally weaken corals, making them more susceptible to other problems.

Risks to Food Web, Even as Some Species May Benefit

Other animals such as sea urchins and various forms of plankton do less calcification, or shell building, as calcium carbonate levels decrease. Such changes could have major repercussions for food webs if they lead to significant population reductions. Surprisingly, though, some experiments have found that some species of lobsters, shrimp, and other crustaceans actually calcify more as carbonate levels drop.

So many questions remain open about the ways that various animals will ultimately fare, and how well they might be able to adapt, that the net effects of ocean acidification can’t yet be predicted. This concern has driven scientists to call for legislation to establish a coordinated and substantially expanded U.S. research program.

“To date the amount of research on ocean acidification has been very small,” says Richard Feely, a chemical oceanographer at NOAA’s Pacific Marine Environmental Laboratory in Seattle, Wa., and a strong advocate of expanded acidification research. Kleypas echoes that sentiment. “In the U.S., we keep saying we’ve got to get this research going, we’ve got to get this research going,” she says, “In Europe they’ve already got some pretty big programs spun up, but here we are still crying.”

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Mark Schrope, The Yale forum on climate change & the media, 28 September 2009. Full article.