Thanks to the marine scientists at the University of South Florida, we now know what has been causing the long spine urchins to die off. It's a specific species of ciliate – called a scuticociliate.
https://scitechdaily.com/sea-urchin...roscopic-menace-behind-massive-die-off-event/
https://scitechdaily.com/sea-urchin...roscopic-menace-behind-massive-die-off-event/