OCEAN ACIDIFICATION ACCELERATES
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 in 65 million years. The change may be too fast for marine animals to adapt.
Scientists 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. Their research
appears in Nature Geoscience.
During this event, which saw a 5-6°C increase in surface water temperature, the oceans acidified and dissolved large quantities of carbonate rocks. All this happened over thousands of years - very sudden from a geological viewpoint. The tiny animals and plants that make up the plankton at the surface of the sea did not suffer much during the event, perhaps because they moved to cooler waters or had time to adapt to changing conditions. Even so, the Palaeocene-Eocene acidification was severe enough to kill off many benthic foraminifers, tiny organisms that live at the bottom of the sea protected by calcium carbonate shells.
This mass extinction has been linked to the high levels of carbon dioxide dissolved in seawater making it difficult for foraminifers to build their shells.
Nowadays, ocean chemistry may be changing even faster. 'What we found was a geologically unprecedented rate of acidification,' says co-author Dr Andy Ridgwell. The change seen today is taking place over hundreds of years, and this could be too much for marine life to handle. 'Given that we had an extinction in the past, it's quite possible that this will happen again in the future,' Ridgwell explains.
Benthic foraminifers might not attract as much sympathy as giant pandas, but their demise 'has implications for the cycling of nutrients and it's a good indication of the extent to which we're affecting the oceans,' he adds, suggesting that even ocean organisms may struggle this time.
Scientists have an idea of the consequences of ocean acidification on marine animals such as foraminifers or corals thanks mainly to experiments. But how will animals adapt to changing conditions? 'Experiments don't tell what will happen over 100 years', says Ridgwell. 'And we can't wait 100 years.'
Editorial Comment : Excellent far-sighted article -= should encourage more youngsters to take up marine biological research !!