The world's oceans are becoming acidic at a faster rate than at any time in the last 65 million years, threatening marine life and food supplies across the globe, according to a new study.
Louise Gray, The Telegraph 15 Feb 10;
Researchers from the University of Bristol looked at how levels of acid in the ocean have changed over history.
They found that as ocean acidification accelerated it caused mass extinctions at the bottom of the food chain that could threaten whole ecosystems in the future.
The rapid acidification today is being caused by the massive amount of carbon dioxide being pumped out by cars and factories every year, which is absorbed by the water. Since the industrial revolution acidity in the seas have increased by 30 per cent.
The last time such a fast change occurred is thought to be 65 million years ago, when some natural event caused ocean acidification and the dinosaurs died out.
The study looked at sediments from around 55 million years ago, when temperature rose by up to 6C and acidification was occurring at a similar rate as today.
It found widespread extinction of tiny organisms that live on the bottom of the ocean. Ocean acidification can dissolve the carbonate shells of marine organisms and cause muscle wastage and dwarfism in other species.
Andy Ridgwell, lead author of the paper published in Nature Geoscience, said it could mean problems for humans in the future.
"Unlike surface plankton dwelling in a variable habitat, organisms living deep down on the ocean floor are adapted to much more stable conditions. A rapid and severe geochemical change in their environment would make their survival precarious.
"The widespread extinction of these ocean floor organisms during the Paleocene-Eocene greenhouse warming and acidification event tells us that similar extinctions in the future are possible," he said.
Dr Ridgwell said acidification is actually occurring much faster today than in the examples they looked at from the past therefore "exceeding the rate plankton can adapt" and theatening the basis of much of marine life. This would mean fish and other creatures further up the food chain that human beings eat may be affected as soon as the end of this century.
"There is lots of concern about major disruption to ecosystems. Certainly coral reefs will be eroded, that has an impact on other species. We could see marine ecosystems affected this century," he said.
:: A separate study published in Geoscience found that the glaciers on Greenland are melting much faster than expected because of ocean currents bringing warm water into the area. If the warming continues it could cause sea levels to rise by 3ft, three times as much as previous estimates, by 2100.
Oceans' acidity rate is soaring, claims study
Steve Connor, The Independent 15 Feb 10;
The rate at which the oceans are becoming more acidic is greater today than at any time in tens of millions of years, according to a new study.
Rapidly rising concentrations of carbon dioxide in the atmosphere mean that the rate of ocean acidification is the fastest since the age of the dinosaurs, which became extinct 65m years ago, scientists believe.
The oceans are likely to become so acidic in coming centuries that they will become uninhabitable for vast swathes of life, especially the little-studied organisms on the deep-sea floor which are a vital link in the marine food chain.
Scientists have concluded, in a study published today in the journal Nature Genetics, that the current rate of ocean acidification is up to 10 times faster than 55m years ago – the last time the deep oceans became so acidic.
This is because of the speed at which carbon-dioxide concentrations are rising in the atmosphere. This carbon dioxide dissolves in seawater at the sea surface to form carbonic acid. The increased acidity of the water affects the amount of dissolved carbonate minerals that are available for marine organisms to use in forming their shells and hard skeletons.
When the oceans became acidified in a similar way about 55m years ago, it resulted in a mass extinction of deep-sea marine organisms, especially those living in the sediments of the sea floor, which can be studied geologically through changes to rock formations, said Dr Andy Ridgwell of the University of Bristol.
"Unlike surface plankton dwelling in a variable habitat, organisms living deep down on the ocean floor are adapted to much more stable conditions. A rapid and severe geochemical change in their environment would make their survival precarious," he said.
Studies also suggest that temperatures of the surface ocean rose, and carbon-dioxide levels increased over a period of a few thousand years.
The latest study compared these changes with predicted changes to ocean acidity resulting from continuing increases in concentrations of man-made carbon dioxide expected this century.
