Acid ocean warning

Scientists have warned that ocean acidification could lead to widespread extinctions of marine animals.

Ocean acidification was high on the agenda of the Climate Change Congress in Copenhagen in March, where scientists predicted that the rate of future ocean acidification would be unprecedented in the last 65 million years.

The acidity of the sea is rising due to increases in atmospheric carbon dioxide from burning fossil fuels. A quarter of carbon dioxide emitted into the atmosphere is absorbed by the sea and forms acid. Since the Industrial Revolution, the acidity of the surface of the sea has risen by 30 per cent.

Higher acidity affects the ability of marine organisms such as shellfish, lobsters and corals to build their skeletons and shells. This could affect the fishing industry and lead to the erosion and loss of coral reefs, which support marine animals, protect shorelines from erosion and flooding, and fuel tourist industries.

Dr Andy Ridgwell, a Royal Society University research fellow at the University of Bristol, said: ‘We’ve known about climate change for many decades, but it’s only in the last ten years or so that we’ve cottoned on to ocean acidification, which we call ‘the other CO2 problem’, the first problem being climate change.’

‘Corals have gone extinct before and they re-emerge in 10-20 million years. If they become extinct now, they could return in 20 million years time. But that’s a lot of future generations who will just have pictures of corals in books.’

Dr Jason Hall-Spencer from Plymouth University has been researching the effects of acidification on marine organisms off the island of Ischia in the Bay of Naples, Italy, where volcanic vents release CO2 into the sea water. Globally, the average pH of the sea is around 8.1, but around the volcanic vents, it can fall as low as 7.4.

Dr Hall-Spencer said: ‘Previous studies have been small-scale, short-term and laboratory-based, so it has been very difficult to predict the wider effects of increasing CO2 emissions on marine life. We show how whole marine communities and ecosystems change due to the long-term effects of acidification.’

The research found there were fewer stony corals, sea urchins and coralline algae in water with a lower pH, and that snails’ shells were dissolving. Dr Hall-Spencer said: ‘Our observations verify concerns, based on laboratory experiments and model predictions, that marine food webs will be severely disrupted and major ecological tipping points are likely if human CO2 emissions continue unabated.’

DIVE MAGAZINE, 2 April 2009. Article.

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