The black ice (IMAGE) Aarhus University Caption When the ice becomes badly affected by algae, it is more black than it is white. Previously, researchers believed that the colour was due to dust that settled on the ice. Today, we know that the black colour is caused by tiny algae. Credit Laura Halbach Usage Restrictions May only be used for telling about this research. 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.