Feely and his research team found in laboratory test that the water near the ocean surface with added con can cause shells of marine animals, including corals, snails and p to dissolve. Carbon dioxide levels that may occur in the seas by the end of the century could reduce the amount of calcium in shells by 25 to 45 percent, the researchers said. That process hasn't yet been studied in the oceans, he noted, but the lab findings indicate a need for concern.