An apocalyptic serial killer of sea urchins is on the loose, scientists are warning—and the path of destruction it’s created in recent years is likely more devastating than we knew.
An international team of researchers has documented a mass die-off of black sea urchins (Diadema africanum) that began in the Canary Islands around mid-2022. The loss of life was so extensive that it could lead to a permanent local extinction of the species, they found. Even worse, the outbreak appears to be just one chain in an ongoing epidemic that threatens to rout sea urchin populations across the globe.
“D. africanum mass mortalities in the Canary Islands may represent a potential link in what may be considered a marine pandemic,” the authors wrote in their paper, published last month in the journal Frontiers in Marine Science.
A mass extinction
Times have been tough for Diadema sea urchins these past few years.
Since 2022, there have been numerous urchin die-offs, or mass mortality events, in the waters of the Atlantic and Indian Oceans. The earliest known and most notable of these outbreaks devastated populations of the long-spined sea urchin (Diadema antillarum) living around the Caribbean Islands and Florida. More recently, there was another die-off recorded in the Gulf of Oman starting in 2023 (near Iran and Pakistan) and another recorded off the coast of Réunion Island near southern Africa in 2024.
Concurrent to these outbreaks, the study researchers say, D. africanum urchins living in the Canary Islands near northwestern Africa began to die off en masse between 2022 and 2023. It’s only now, though, that they’ve been able to comprehensively assess what happened to the urchins, thanks in large part to data collected by citizen scientists.
D. africanum urchins in the Canary Islands have bounced back from other die-offs with relative ease, even as recently as 2018. The sheer amount of destruction documented this time around was unprecented, however. Across several islands, they found no signs of juvenile urchins living in the area after the initial die-off.
“In other words, the die-off of the adult urchins has been so widespread that the species is no longer able to produce a next generation; if no recruitment occurs, the species may disappear from the region’s ecosystem,” said study author Omri Bronstein, a zoologist at Tel Aviv University, in a statement released by Frontiers, the study’s publisher.
A dire warning sign
If that isn’t bad enough, the location and timing of this die-off is also concerning. It’s possible, though still not confirmed, that the Canary Island outbreak is the missing link tying the Atlantic Ocean die-offs to the later die-offs seen in the Indian Ocean. And if that’s true, then we’re probably looking at a pandemic that could continue to spread wider into the Pacific Ocean and beyond.
Sea urchins are crucial to their shallow tropical environments since they feed on and keep algae populations in check that might otherwise threaten the survival of coral reefs. So the loss of these invertebrates could have untold destructive effects on other marine life.
Scientists have made some headway on the urchin problem. In 2023, a research team conclusively discovered at least one major cause of the Caribbean die-off: a particular species of ciliate—microscopic protists with hair-like projections called cilia. Different researchers have since linked the pathogen to other recent die-offs as well.
Because no specimens were collected at the time, researchers say they still can’t conclusively link the Canary Island outbreak to the same cause. But it’s clear more has to be done to protect the world’s remaining sea urchins from whatever is coming after them.
