Audio: Listen to marine ecologist Joanie Kleypas discuss ocean acidification with New Scientist’s Ivan Semeniuk (mp3 file, 7MB). Listen to all the New Scientist podcasts here.

A few years ago, Victoria Fabry saw the future of the world’s oceans in a plastic jar. She was aboard a research vessel in the frigid waters of the North Pacific, carrying out experiments on a species of pteropod called Clio pyramidata – frisky little molluscs with shells up to a centimetre long and flaps on their bodies that they use to swim in a way that resembles butterfly flight.

Something strange was happening in Fabry’s jars. “The pteropods were still swimming like billy-o, but their shells were visibly dissolving,” says Fabry, a biologist from California State University San Marcos. “I could see it with the naked eye.”

She realised that the animals’ respiration had increased the carbon dioxide concentration in the jars, which had been sealed for 48 hours, changing the water’s chemistry to a point where the calcium carbonate in the pteropods’ shells had started to dissolve. Fabry and her colleagues were aware that at some point in the future the massive influx of carbon dioxide from human activity might reduce the alkalinity of the oceans. “But this was way before anybody thought such a trend would affect organisms like these.” What Fabry had stumbled on was a hint of “the other CO 2 problem”.

It has taken several decades and hundreds of millions of dollars’ worth of research for climate change to be recognised as a serious threat. But another result of our fossil fuel habit – ocean acidification – …