Biosphere 2's artificial reef

The Oracle ecosystem comprises a 700,000-gallon aquarium of artificial seawater, with a community of coral reef life which mimics key aspects of real reef ecosystems.

Dr Langdon says the research suggests that coral growth could be reduced by up to 40% from pre-industrial levels over the next 65 years.

He said: "This is the first real evidence that increasing atmospheric CO2 levels have a negative impact on a major Earth ecosystem."

By the middle of this century, the team believes, rises in CO2 levels, caused mainly by the burning of fossil fuels, will reduce by 30% the carbonate ion concentration of the surface ocean.

Protection

When Dr Langdon changed the carbonate concentration in the Bosphere 2 tank to the projected level, he observed a significant reduction in calcification rates for the coral and coralline algae.

Reefs are home to many species

He believes his research has some significant implications, for example over the role of reefs as natural breakwaters which can give protection against beach erosion.

Dr Langdon is also concerned that reefs stressed by higher CO2 levels, which could be beneficial on land, will be more vulnerable to other threats, like over-fishing or pollution.

He said: "While some terrestrial ecosystems may actually benefit from elevated CO2 levels, that does not appear to be the case for shallow marine ecosystems like a coral reef."