Taking Global Warming for a Swim

by Matt Getty

April 1, 2010

Tom Arnold, associate professor of biology, tests the FOCE system at the Sanibel-Captiva Conservation Foundation Marine Laboratory in Sanibel, Fla.

Associate Professor of Biology Tom Arnold wants to take the conversation about greenhouse gases and carbon emissions out of the air and into the ocean.

“Everybody has been worried about the CO2 in the atmosphere, but when CO2 enters the ocean, it essentially carbonates the water—they call it ocean acidification,” he explains. “Imagine if you took a piece of chalk and dropped it into a Coke can. It’s going to fizz and dissolve, right? Well, chalk is very similar to what coral skeletons, scallop shells and oyster shells are made of, and even slight drops in ocean pH caused by carbonation can dissolve skeletons and shells or prevent them from forming in the first place.”

Just imagining chalk fizzing in a can of soda, however, isn’t enough to convince skeptics that carbon is a threat to the world’s oceans. Scientists like Arnold, who has long studied distressed underwater organisms like sea grass, need to show exactly how the 0.2 unit drop in ocean pH expected during the next 50 years will affect coral reefs and shellfish populations.

“Now that we’ve recognized the magnitude of the problem, everybody wants to study it,” he says, “but we hadn’t come up with a device that could show how underwater organisms would react to increased acidification.”

So last year Arnold built that device—the free-ocean-carbon-enrichment (FOCE) system. Powered by solar energy, the FOCE system acidifies a small amount of ocean water in a series of 18-inch-diameter underwater chambers, enabling scientists to observe the effects of future increases in ocean acidification.

Having field tested it last summer in Sanibel, Fla., Arnold is seeking funding for a prolonged study with the FOCE system and enlisting a team of Dickinson students to collaborate on that study. Knowing that scientists are already behind the curve on attacking this problem, he’s eager to use the first-of-its-kind device to show how climate change, if unchecked, threatens vital underwater ecosystems like the Great Barrier Reef.

“The scary thing is very few people were paying any attention to ocean acidification, even in the scientific community,” Arnold says. “So now we’ve got to move fast. The ocean has already decreased 0.1 pH units on average. … This is already happening—and it’s happening pretty quickly.”