Purple Sea Urchins, before Die-Off (IMAGE) University of California - Davis Caption These are tide pools of purple sea urchins, who experienced nearly 100 percent mortality after a die-off in Northern California in 2011. Credit Laura Jurgens/UC Davis Bodega Marine Laboratory Usage Restrictions Provide credit. 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.