Climate Change: Marine Snail Shells Dissolved by Acid Ocean

The shells of marine snails are being dissolved by ocean acidification, caused by carbon dioxide produced by burning fossil fuels.

The finding is the first evidence that ocean acidification is damaging marine wildlife and scientists believe it could have a massive impact on ecosystems.

Researchers from the British Antarctic Survey and the University of East Anglia found that marine snails, named pteropods, which live in the seas around Antarctica, are being dissolved by ocean acids.

Pteropods are the size of a pinhead - around 1cm - and they live to depths of 200m, so are relatively close to the ocean surface.

They are a valuable food source for birds and fish and play an important role in the oceanic carbon cycle - the method by which carbon is absorbed and released by the ocean.

Geraint Tarling, from BAS, said: "Pteropods are an important food source for fish and birds as well as a good indicator of ecosystem health.

"The tiny snails do not necessarily die as a result of their shells dissolving, however it may increase their vulnerability to predation and infection consequently having an impact to other parts of the food web."

Pteropod shells are made of calcium carbonate - or aragonite - which dissolves rapidly when its saturation in seawater falls below a certain level. Normally, this level is about 1km, but scientists predict the 'threshold' could reach the surface by 2100.

Ocean acidification is caused by the uptake of carbon dioxide from the atmosphere. In a process known as upwelling, cooler and nutrient-rich water is pushed towards the ocean surface, replacing the warmer and nutrient-deficient surface water.

Upwelled water is more corrosive to aragonite. The addition of acids to the water means the snail shells are dissolved "severely".

"Human-induced carbon dioxide contributed"

Dr Nina Nina Bednarsek, from the National Oceanic and Atmospheric Administration, said: "We know that the seawater becomes more corrosive to aragonite shells below a certain depth - called the 'saturation horizon' - which occurs at around 1000m depth.

"However, at one of our sampling sites, we discovered that this point was reached at 200m depth, through a combination of natural upwelling and ocean acidification.

"Marine snails - pteropods - live in this top layer of the ocean. The corrosive properties of the water caused shells of live animals to be severely dissolved and this demonstrates how vulnerable pteropods are.

"Ocean acidification, resulting from the addition of human-induced carbon dioxide, contributed to this dissolution."

The United Nations is currently in talks over a new climate change pact in Qutar. Three years ago, attempts to create a new climate treaty failed in Copenhagen, but the UN gave itself until 2015 to come to a new agreement.

The concentration of greenhouse gases, such as carbon dioxide has increased by 20 per cent since 2000, a recent UN report said.

However, climate change activists criticise the treaty talks, with many saying they are progressing too slowly.

Martin Kaiser, Greenpeace climate campaigner, said: "Climate change is no longer some distant threat for the future, but is with us today.

"At the end of a year that has seen the impacts of climate change devastate homes and families around the world, the need for action is obvious and urgent."