Affected Terrapin Turtles (IMAGE) University of Missouri-Columbia Caption When diving for long periods of time, turtles use stored calcium in their shells to help maintain a normal physiological state while they hold their breath. Exposure to PCBs could affect their ability to do this. Credit University of Missouri Usage Restrictions None License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.