Carbon dioxide, created in large part by burning fossil fuels, becomes carbonic acid when it dissolves in salt water and corrodes the shells of marine organisms.
"If CO2 from human activities continues to rise, the oceans will become so acidic by 2100 it could threaten marine life in ways we can't anticipate," said Ken Caldeira, a co-author of the report who recently joined Carnegie Institute's Department of Global Ecology in Stanford, Calif.
Royal Society Chairman John Raven called for "decisive and significant" action by G8 world leaders meeting next week in Scotland to reduce carbon dioxide emissions.
"The oceans play a vital role in the earth's climate and other natural systems which are all interconnected," Raven said. "Failure to do so may mean that there is no place in the oceans of the future for many of the species and ecosystems that we know today."