Acid oceans a threat to mussels, say Scots experts

Acidic water makes mussel shells more brittle. Picture: Getty
Acidic water makes mussel shells more brittle. Picture: Getty
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The world’s mussel population could be under threat as climate change causes the oceans to become more acidic, scientists have warned.

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 mussels need to generate their shells, according to scientists. They also found that mussels may have an in-built biological defence mechanism which boosts shell development when water temperatures rise by 2C.

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.

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“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. 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 temperature of the water was increased by 2C. This might suggest that the mussels are reverting to ancestral evolutionary mechanisms to mitigate the effects of increased acidity. ”

The shellfish industry is worth more than £250m a year to the UK economy with a large part accounted for by mussels and oysters, the UK Department for Environment, Food and Rural Affairs reported in 2012.

Mussels contribute around £7m to the Scottish economy alone, with other shellfish accounting for £1.4 million, according to the Scottish Government’s marine atlas, published in 2011.

WWF Scotland director Lang Banks said: “This important research adds to our growing knowledge about the potential harmful impacts of climate change upon our marine environment. While some marine species will be able to adapt, many others will not. This is not only bad news for those affected species, but bad news for any communities or businesses that depend upon those species for their livelihoods.”

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