Acidic oceans: fish lose ability to smell danger

Fish face losing their ability to smell danger as the oceans grow more acidic, new research has revealed.

Marine biologists studying the impact of ocean acidification, which occurs when carbon dioxide dissolves in seawater, have found it affects the ability of fish to smell.

They have discovered that young fish reared in water with elevated levels of carbon dioxide in the water become unable to distinguish the scent of predators and even seem attracted to their smell.

The researchers, who will reveal their findings at a conference in Belfast on fish and climate change later this month, showed that in the wild, these fish larvae take greater risks, swimming further from shelter that might hide them from predators.

More of the fish larvae also die in the wild, sparking fears that fish populations could struggle to survive and replenish themselves as oceans become more acidic.

Scientists predict that the world’s oceans will grow increasingly acidic as levels of carbon dioxide in the atmosphere rise due to human activity and dissolve in the sea.

It is already known that ocean acidification will be catastrophic for shellfish as the weakly acidic water makes it harder for them to grow shells.

But this is the first evidence that suggests ocean acidification could also affect fish directly.

Professor Philip Munday, who carried out the research at the school of marine and tropical biology at James Cook University in Queensland, Australia, said: “As atmospheric carbon dioxide increases, so douse the amount dissolved in the sea.

“We have found that levels of carbon dioxide that could occur in the ocean by the end of this century affects the sense of smell and behaviour of fish larvae.

“They exhibit riskier behaviour which makes them more prone to predation.”

The researchers tested the effect of raised carbon dioxide levels in the sea on clown fish and damselfish larvae.

Richard Gray, Telegraph, 18 July 2010. Full article.

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