Scientists fear for future of world’s mussel stocks as oceans turn more acidic

Mussel shells become more brittle when they are formed in more acidic water, Glasgow University has reported in the Royal Society journal Interface. Carbon dioxide in the atmosphere causes the oceans to become more acidic and reduces the concentration of the minerals that mussels need to generate their shells, according to scientists.

However, they also found that mussels may have an in-built biological defence mechanism that boosts shell development when water temperatures rise by 2C.

Research associate Dr Susan Fitzer said: “What we’ve found in the lab is that increased levels of acidification in their habitats have a negative impact on mussels’ ability to create their shells.

“We worked with colleagues in our School of Engineering to examine the toughness of the shells of the mussels in the more acidic water against those in control conditions.

“What we found was that the calcite outer shells of the mussels past a certain threshold of acidity was stiffer and harder, making it more brittle and prone to fracture under pressure, and the aragonite inner shell became softer.”

She added: “This could mean that mussels growing in the wild in the future could be more vulnerable to attack from predators, as well as from the effect of ocean forces.

“As blue mussels are commonly used for human consumption, it could also have an effect on the yields of mussels available for the fishing industry.

“However, we also found that the effect on the mussels’ shells was reduced when the water temperature was increased by 2C. This might suggest that the mussels are reverting to ancestral evolutionary mechanisms to mitigate the effects of increased acidity.

“We’re planning to continue our research in this area in the future.”