Ocean acidification may contribute to global shellfish decline

Washington, October 27 (ANI): In a new study, scientists have found that ocean acidification may contribute to global shellfish decline, as elevated carbon dioxide (CO2) concentrations impede growth and survival of bivalve larvae.

Researchers at the Stony Brook University in the US carried out the study.

In the study, Stephanie Talmage and Professor Chris Gobler showed that the larval stages of these shellfish species are extremely sensitive to enhanced levels of carbon dioxide in seawater.

"In recent decades, we have seen our oceans threatened by overfishing, harmful algal blooms, and warming. Our findings suggest ocean acidification poses an equally serious risk to our ocean resources," said Gobler.

During the past century, the oceans absorbed nearly half of atmospheric carbon dioxide derived from human activities such as burning fossil fuels.

As the ocean absorbs carbon dioxide it becomes more acidic and has a lower concentration of carbonate, which shell-making organisms use to produce their calcium carbonate structures, such as the shells of shellfish.

In lab experiments, Talmage and Gobler examined the growth and survivorship of larvae from three species of commercially and ecologically valuable shellfish.

They raised the larvae in containers bubbled with different levels of carbon dioxide in the range of concentrations that are projected to occur in the oceans during the 21st century and beyond.

Under carbon dioxide concentrations estimated to occur later this century, clam and scallop larvae showed a more than 50 percent decline in survival.

These larvae were also smaller and took longer to develop into the juvenile stage.

Oysters also grew more slowly at this level of CO2, but their survival was only diminished at carbon dioxide levels expected next century.

"The longer time spent in the larval stage is frightening on several levels. Shellfish larvae are free swimming. The more time they spend in the water column, the greater their risk of being eaten by a predator," said Talmage.

"A small change in the timing of the larval development could have a large effect on the number of larvae that survive to the juvenile stage and could dramatically alter the composition of the entire population," she added.

"We've blamed shellfish declines on brown tide, overfishing, and local low-oxygen events. However, it's likely that ocean acidification also contributes to shellfish declines," she said.

Talmage and Gobler hope their work might help improve the success rate of shellfish restoration projects. (ANI)