Death of the Coral Reef 'Lawn-mowers'

Long-spined sea urchins eat the algae growing on coral reefs. If this algae remains in place, stops the coral organisms feeding effectively, So, the presence of Long-spined sea urchins, keeps reefs in a healthy condition. There's recently been, however, from the US to the Caribbean, a massed die-off of urchins. Why? (https://www.theguardian.com/environment/2023/apr/24/scientists-discover-why-sea-urchins-are-dying-off-from-us-to-the-caribbean). A study, in Science Advances, has implicated infection by a single cell parasite in the mass urchin die-off. There was a similar event in the 1980s, when 98% of Long-spined sea urchins were wiped out. It's probable that the same parasite, philaster, was involved but no samples were collected at that time. Having a better understanding of complex interactions can help improve reef conservation.