Since the birth of the industrial revolution, ocean pH has dropped by 0.1 units. That might not sound like much until you realise that a 0.1 unit fall is a 30% increase in acidity¹. And, with predictions that ocean pH will continue plummeting²（垂直落下） , ecologists are becoming increasingly concerned about the impact of ocean acidification on marine³ populations. Brian Gaylord and his colleagues from the University of California at Davis explain that the open-coast mussel（蚌） , Mytilus californianus, is a foundation species for many coastal⁴ ecosystems⁵ on the exposed northwestern coasts of North America, yet no one knew how ocean acidification might affect this keystone organism. So, the team decided⁶ to find out how a fall in pH might impinge on（影响，撞击） the earliest settlers to colonise an exposed rocky outcrop, M. californianus larvae⁷, and publish their discovery that the larvae are significantly weakened by ocean acidification in The Journal of Experimental Biology at http://jeb.biologists.org/content/214/15/2586.abstract. Growing freshly fertilized⁸ M. californianus larvae in seawater laced with carbon dioxide ranging from the modern level of 380 p.p.m.CO2 up to a 'fossil-fuel intensive' scenario⁹ of 970 p.p.m.CO2, the team allowed the larvae to develop for 8 days. Then they analysed the strength, size and thickness of the larvae's shells and found that acidification of the mollusc's seawater has a strong impact on shell strength. Shockingly, the shells of 5 day old larvae raised in 970 p.p.m.CO2 were 20% weaker than those of larvae reared at the current CO2 level, while the shells of larvae reared at 540 p.p.m.CO2 were only 13% weaker. The team also found that after 8 days at 970 p.p.m.CO2 the shells were up to 15% thinner and 5% smaller, and the body masses of the molluscs within the shell were as much as 33% smaller than those of mussels grown at modern CO2 levels.

'The observed ocean acidification-induced decrease in shell integrity in M. californianus represents a clear decline in function,' say Gaylord and his colleagues, who also warn that, 'Such reductions may in fact be common in bivalves（双壳类） .' Outlining the potential ecological¹⁰ consequences of ocean acidification, the team suspects that larvae weakened by rising CO2 levels could develop more slowly or, alternatively, they could be more vulnerable to predation, more susceptible¹¹ to stress and at greater risk of desiccation（干燥） . Ultimately these factors could conspire¹² to reduce the mussel's survival and destroy the delicate balance that exists in today's coastal ecosystems.