Quagga and Zebra Mussel Invasion Risk Map (IMAGE) Ecological Society of America Caption Map of Dreissena invasion risk classes for ecoregions of the contigous US based on calcium concentrations in streams and rivers. Credit Whittier et. al. 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.