Free-swimming snails show shell damage in water conditions that are likely to become more prevalent as the climate warms. By 2050, the top 200 metres of the Southern Ocean are likely to become under-saturated in a form of calcium carbonate called aragonite — a component of many shells. If aragonite structures are placed in waters in which the saturation state is less than one, they gradually dissolve.


Geraint Tarling of the British Antarctic Survey in Cambridge, UK, and his team analysed the shells of Limacina helicina antarctica pteropods (pictured) captured from the top 200 metres in an upwelling region of the Southern Ocean in 2008. Their shells were thinner and more porous than those captured elsewhere. In the laboratory, eight days of immersion in waters with a saturation state of between 0.94 and 1.12 produced similar levels of damage. Aragonite-shelled animals, important to food and carbon cycles, may decline sooner than expected in the Southern Ocean, the authors say.

Nature Geosci. (2012)