Diatom Red (IMAGE) UiT The Arctic University of Norway Caption Diatoms have valves that easily dissolve in salty ocean water. But they leave traces of molecules in the sediments that scientists can look for to determine how the populations of algae developed in the past. Credit Ulrike Hoff Usage Restrictions No derivatives. Attribution 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.