The 2022 Diadema antillarum die-off event: Comparisons with the 1983-1984 mass mortality

The 1983-1984 die-off of the long-spined sea urchin Diadema antillarum stands out as a catastrophic marine event because its detrimental effects on Caribbean coral reefs. Without grazing activities this key herbivore, turf and macroalgae became dominant benthic group, inhibiting recruitment compromising reef recovery from other disturbances. In decades that followed, D. populations was slow to non-existent. late January 2022, new mass mortality first observed in U.S. Virgin Islands. We documented spread extent using an online survey. Infected individuals were closely monitored lab record signs illness, while large population Saba, Dutch Caribbean, surveyed weekly before during determine lethality event. Within four months distributed over 1,300 km north south 2,500 east west. Whereas advanced mostly with currents, 2022 has appeared far more quickly geographically distant areas. First observations each jurisdiction often close harbor areas, which, together their rapid appearance, suggests anthropogenic factors may have contributed causative agent. illness sick very similar those recorded die-off: lack tube feet control, spine reaction followed by loss, necrosis epidermis both wild urchins. Affected succumbed fast; within month at had decreased 4.05 per m 2 0.05 . Lethality can therefore be high 99%. full is not currently known. slower summer might indicate coming (temporary) standstill. If case, some will remain unaffected potentially supply larvae downstream areas augment natural processes. addition, several rehabilitation approaches been developed past decade are ready for scale implementation. However, active conservation restoration should distract primary goal identifying cause and, if possible, implementing actions decrease likelihood future events.