The shift disrupts ocean chemistry and attacks the “building blocks needed by many marine organisms, such as corals and shellfish, to produce their skeletons, shells and other hard structures”, they said.
On some projections, levels of acidification in 80 per cent of Arctic seas would be corrosive to clams that are vital to the food web by 2060, it said.
And “coral reefs may be dissolving globally” if atmospheric levels of carbon dioxide were to rise to 550 parts per million (ppm) from a current 387 ppm
Corals are home to many species of fish.
“These changes in ocean chemistry are irreversible for many thousands of years and the biological consequences could last much longer,” they said.
Martin Rees, president of the Royal Society, the British science academy, said there may be an “underwater catastrophe”.
“The effects will be seen worldwide, threatening food security, reducing coastal protection and damaging the local economies that may be least able to tolerate it,” he said.
The academies said that if current rates of carbon emissions continue until 2050, computer models indicate “the oceans will be more acidic than they have been for tens of millions of years”.