Ocean acidification is speeding up

Carbon dioxide released from fossil fuels and dissolved in the ocean is making seawater more acidic and causing trouble for marine life. Now a new model suggests that seawater is acidifying at a rate that exceeds anything seen on Earth over the past 65 million years. The speed of change may in fact be faster than what marine animals can cope with.

Dr Andy Ridgwell and colleague Dr Daniela Schmidt, from the University of Bristol, developed a model to compare current predictions of ocean acidification with what happened during a greenhouse gas event 55 million years ago, called the Palaeocene-Eocene thermal maximum (PETM).

During this event, which saw a 5-6°C increase in surface water temperature, the oceans acidified and a massive amount of carbonate rocks was dissolved as a consequence. All this happened over thousands of years. It may look like a lot of time, but on a geological scale it was very sudden.

The tiny animals and plants that make up the plankton at the surface of the sea did not suffer much during the event, possibly because they migrated to cooler waters or because they had time to adapt to the new conditions. Even so, the Palaeocene-Eocene acidification event was severe enough to cause the extinction of many benthic foraminifers, tiny organisms that live at the bottom of the sea protected by calcium carbonate shells.

Sara Coelho, Planet Earth online, 15 February 2010. Full article.

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