Oceans fail the acid test as carbon emissions rise

It is the little mentioned flip side of global warming – the acidification of the world’s oceans. Now new research shows that, as predicted, it is harming sea life.

Even if climate change were not taking place, the process provides compelling cause for reducing emissions of carbon dioxide, for they are powering what scientists believe to be the most profound change in the chemistry of the oceans in millions of years. And its effects cannot be reversed in less than tens of millennia.

The souring of the seas is happening because their waters absorb much of the carbon dioxide released by humanity. Indeed they have so far soaked up about half of the greenhouse gas emitted since the beginning of the industrial revolution, some 500 billion tons of it. This has done the world a service by slowing down global warming – it would already be far out of control if all that pollution had stayed in the atmosphere – but at a cost to the oceans.

The gas dissolves in the water to produce carbonic acid, souring its natural alkalinity. Measurements show that, as a result, the seas have become nearly a third more acidic than they were some 250 years ago, and – according to a report by the blue-chip Royal Society – are now more so than they have been in “hundreds of millennia”.

The acid attacks the normally plentiful calcium carbonate, used by marine life to build protective shells and by corals to construct their reefs. Plankton, which form the base of the oceans’ food chain, are among the species in danger.

Now research by the British Antarctic Survey, the University of East Anglia, the Woods Hole Oceanographic Institution and the US Government’s National Oceanic and Atmospheric Administration has established that the process is indeed damaging marine creatures. It discovered “severe dissolution” of the shells of living pteropods – tiny snails no bigger than a pinhead – near an area of upwelling in the Southern Ocean.

Upwelling water, pushed upwards from the deep sea to the surface, is naturally more corrosive to the type of calcium carbonate used by the snails in the first place, but the scientists found that it was the added acidity brought about by dissolved carbon dioxide that enabled it to case such severe damage. “The finding”, says the British Antarctic Survey “supports predictions that the impact of ocean acidification on marine ecosystems and food webs may be significant.”

A report by the European Project on Ocean Acidification concluded three years ago that the rate of change in oceanic chemistry “is, to the best of our knowledge, many times faster than anything previously experienced over the last 55 million years”. And Prof Ulf Reibesell if the Leibnitz Institute of Marine Sciences in Kiel, Germany, has warned that if the process continues as predicted, the oceans will reach a state unprecedented at any time in the last 20 million years.

Experts add that there is no practical way to turn back the acidification once it has occurred; all that can be down is to let nature take its course, a process that would take tens of thousands of years to return the seas to what they once were.

Britain may be particularly affected. For yet another report, by the marine group Oceana, has concluded that is the third most vulnerable country on earth to the process after Japan and France – because its waters contain one of world’s most productive fisheries, and because the seas around out island are cold and particularly salty, making them especially prone to acidification.

Geoffrey Lean, The Telegraph, 28 November 2012. Article.

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