Nature Geosci. 10.1038/ngeo755 (2010)

Credit: NASA

Marine plankton survived a period of intense ocean warming and acidification some 55 million years ago. But their future descendants might not be so lucky, suggests a new study.

Using an Earth-system model called GENIE-1, Andy Ridgwell and Daniela Schmidt of Bristol University in the UK compared possible future levels of ocean acidity to those experienced during the Palaeocene-Eocene Thermal Maximum (PETM), a period of warming during which a massive amount of carbon was released into the atmosphere. Ridgwell and Schmidt ran their model assuming a 'business as usual' greenhouse gas emissions scenario until 2100 and a linear decline in emissions thereafter. This gives a total carbon release of 2.18 trillion tonnes, similar to the amount thought to have been released during the PETM.

They found that in the future the deep ocean could become undersaturated with carbonate, the mineral form of carbon used by calcareous organisms for building shells and skeletons, to an even worse extent than during the PETM. At the ocean surface, the rate of acidification could exceed that experienced during the PETM, potentially challenging the ability of plankton to adapt.