Current and future increases in ocean acidity – brought about by rising levels of carbon dioxide – could be detrimental to commercially and ecologically valuable shellfish populations, according to researchers at Stony Brook University in New York state, who found that shellfish larvae are extremely sensitive to CO2 concentrations in seawater.

The world’s oceans absorb up to half of all atmospheric CO2 derived from human activity. This increases the acidity of seawater, which, in turn, lowers the concentration of calcium carbonate, the compound from which shellfish make their shells.

In laboratory experiments, Professor Chris Gobler and PhD candidate Stephanie Talmage monitored the growth and survival of the larval stages of hard clams, bay scallops and eastern oysters exposed to varying levels of CO2. A 50 per cent decline was observed in the survival rates of clam and scallop larvae raised in seawater with CO2 concentrations expected by the end of this century. All three species also took longer to develop into the juvenile stage.

Even a small change in the timing of larval development could have a significant effect on survival into the juvenile stage, according to Talmage, since shellfish larvae are free-swimming and particularly vulnerable to predation.

‘We have seen our oceans threatened by overfishing, harmful algal blooms and warming,’ said Gobler. ‘Our findings suggest ocean acidification poses an equally serious risk to our ocean resources.’

Puffin O’Hanlon
January 2010