Shells as seawater sensors (IMAGE) Iowa State University Caption Alan Wanamaker of Iowa State University collects clam shells from the Gulf of Maine. Wanamaker's lab analyzes shell layers to build a history of seawater characteristics, including temperature, ocean currents and water sources. Credit Photo by Erin Beirne Usage Restrictions None License Original 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.