Adapting to an acid ocean

Posted on the EPOCA blog 17 May 2011

Acidification has been called the ‘evil twin’ of warming waters when it comes to climate change’s impacts on the ocean. The ocean has become 30% more acidic since the industrial revolution, a trend that is expected to have devastating impacts on corals and any marine life with a carbonate shell — one study has even shown that acidification can interfere with some fish’s sense of smell and homing abilities (Munday P., PNAS, 106, 1848-1852; 2009).

Researchers are starting to investigate whether some organisms might be able to evolve their way out of the problem. BC’s sea urchins might be able to do just that, PhD student Jenn Sunday of Simon Fraser University near Vancouver, Canada, told the Society of Conservation Biology’s International Marine Conservation Congress on Sunday.

Sunday bred both mussels and urchins and exposed them to water at pH 8.1 (fairly normal for today), and pH 7.8 (expected by 2100). She measured the length of larvae produced from the matings (bigger larvae being healthier), and found that urchins had a much broader range of variability in their offspring size than the mussels. From that, along with an estimate of the heritability of this feature, she says it’s very possible the sea urchin larvae will be able to evolve back to their normal size within 50 years, while the mussels don’t stand a chance. The study is only preliminary — Sunday says she didn’t have enough larvae in her study to narrow the heritability ranges to a reasonable degree, and there are a bunch of other unknowns, including the reproduction rate of these species. If urchins only replace 10% of their population each year, as one study has hinted, then they won’t be able to keep up with acidification. But if it’s as high as 30% — which it very well could be — then they have a very good chance.

Other organisms might also fare well. Previous studies have shown that British Columbia’s common sea stars actually grow faster and eat more in acidic conditions (Gooding, R.A, Harley C.D.G, and Tang E. PNAS Early Edition May 25, 2009). It could be that more food and an increased metabolism might outweigh the effects of acid waters, says Sunday.

Stephen Palumbi, director of Stanford University’s Hopkins Marine Station, thinks there’s a lot of good research to be done on the possible evolutionary responses of ocean creatures to acidification. “How many animals regulate their temperature? Some. How many regulate their acidity? Every single one,” he says. It would also be interesting, he adds, to see if and how communities can alter the acidity of their local surroundings. “Can a healthy ecosystem regulate pH?” he wonders. If so, that would provide yet another good reason to repair marine systems.

Ivan Semeniuk on behalf of Nicola Jones. Nature News blog, 15 May 2011. Article.