Climate change will leave a sour taste in our mouths – literally: Study shows ocean acidification affects the flavour of shellfish

Photo credit: Alamy

Photo credit: Alamy

It is a popular appetiser at this time of year, but Marie Rose could soon be a lot less paletable, according to a new study.

Marine biologists have found that shellfish take on a sour flavour if they are reared in slightly acidified sea water. They warn that as the planet’s oceans grow more acidic, due to rising carbon dioxide levels, many of our favourite seafoods could become less appetising.

Climate change experts predict that over the next century, the acidity levels of the world’s oceans could drop from pH8 to pH7.5. Many have warned this could lead to shrimps and prawns struggling to build the shells and skeletons they need to survive.

Now, in the first study to test how ocean acidification could impact on the taste of seafood, researchers at the University of Gothenberg and Plymouth University, found it will also affect their taste.

Dr Sam Dupont, a marine biologist at the University of Gothenberg who led the study, said: ‘Understanding how seafood will be influenced by coming environmental changes such as ocean acidification is a research priority.

‘One major gap in knowledge relates to the fact that many experiments are not considering relevant end points related directly to production and product quality that can have important repercussions for consumers and the seafood market.

‘These results help to prove the concept that ocean acidification can modulate sensory quality of the northern shrimp.’

The researchers, whose work is published in the Journal of Shellfish Research, put hundreds of northern shrimp Pandalus borealis into two tanks of water for three weeks.

They were either placed in sea water with a pH of 8 – about the same acidity levels as seen in oceans currently – or in a more acidic tank with a pH of 7.5, which is what experts predict could be the acidity of the world’s oceans by 2100.

Both tanks were kept at 11°C (51°F) before they were then assessed by in a taste test by a sensory panel of 30 connoisseurs, who rated them for appearance, texture and taste.

Decreased pH reduced the score significantly for appearance and taste, but not for texture.

Shrimp raised in the waters with the lower pH were 2.6 times more likely to be rated as the worst tasting, while those reared in the less acidic water were 3.4 times more likely to be judged the tastiest.

Also the 63 per cent of the shrimp from the acidic water died during the three weeks.

The results could have profound implications for the seafood industry as it suggests shellfish will become harder as their numbers dwindle, but also demand could decrease as people lose their taste for them.

Dr Dupont added: ‘More research is now needed to evaluate impacts on other seafood species, socioeconomic consequences, and potential options.’

The world’s oceans are thought to absorb approximately half of the carbon dioxide emitted into the atmosphere by dissolving it.

However, when carbon dioxide dissolves in sea water, it forms carbonic acid, causing the pH of the oceans to decrease.

At the moment the oceans are a weak alkaline, so ocean acidification actually refers to making the world’s seas less alkaline.

The impacts of ocean acidification were largely overlooked until the Royal Society published a report in 2005 and in its recent report, the UN Intergovernmental Panel on Climate Change said that the acidity of the world’s oceans has already dropped by 0.1 pH unit since preindustrial periods.

It predicts that this will continue to fall by a further 0.4pH units by 2100.

This acidification leads to lower levels of calcium carbonate in sea water, making it harder for shellfish to form their shells.

Popular seafood like crabs, prawns, mussels, lobsters, clams and oysters all rely upon this chemical as the main building block for their shells.

As many of these species are at the lower end of the marine food web, they provide vital sources of food for fish and other animals.

As their numbers dwindle, larger fish and marine mammals will also struggle to find the nutrients they need.

Professor Kevin Flynn, from the Centre for Sustainable Aquatic Research at Swansea University, told MailOnline: ‘Ocean acidification has the potential to significantly alter ocean life, including fisheries.

‘However, we know very little just now except pieces of the jigsaw. Outputs from research gives contrasting opinions; some indicate little change while others indicate potential for significant change.

‘Changes in taste of seafood could be the least of our problems…the species may not be there to harvest in the first place.

‘Under ocean acidification the food chain as we know it may change, and with it our tastes in seafood will have to change as well.’

Richard Gray, Daily Mail, 22 december 2014. Article.

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