Marine biologists break out in a cold sweat when they think about the impact of greenhouse gases on the oceans. It's not just the fact that global warming raises the temperature of the sea. Scientists are also worried about acidity. The burning of fossil fuels pumps carbon dioxide into the atmosphere, and when it gets absorbed by seawater, it turns into carbonic acid and makes the oceans more acidic.
Warmer waters are stressful for marine life, making organisms like coral more vulnerable to disease. A lower ocean pH--i.e. a more acidic environment--makes it harder for marine invertebrates to construct their shells. But there has been little work looking at the combined effects of warmer waters and stronger acidity.
At a symposium here yesterday, physiologist Gretchen Hofmann of the University of California, Santa Barbara, reported that the combination can be deadly for the purple sea urchin, Strongylocentrotus purpuratus, that she works on. DNA studies are also revealing details about how the urchins battle the stress. "This is cutting edge," says marine ecologist Jane Lubcencko of Oregon State University in Corvallis.