Scientists establish reason for Caribbean sea urchin die-off

Final 12 months, sea urchins within the Caribbean began getting sick — shedding their spines, dying off and throwing reef ecosystems into chaos. Now, scientists suppose they’ve caught the killer on this marine homicide thriller.

A tiny single-celled parasite is accountable for the huge die-off, researchers reported Wednesday within the journal Science Advances.

“The case is closed,” stated examine writer Mya Breitbart, a marine microbiologist on the College of South Florida.


These long-spined sea urchins, or Diadema antillarum, are prickly black creatures that disguise out in reefs throughout the Caribbean. They play a key function as “lawnmowers” of the reef, Breitbart stated, consuming up the algae that grows on corals.

However in January 2022, these animals began exhibiting unusual signs — their sharp spines drooping and falling off, their suction-cup toes dropping their grip — earlier than dying off in droves, from the Virgin Islands to Puerto Rico to Florida.

For marine scientists, it was deja vu: One other die-off swept by means of the area within the Eighties and slashed sea urchin populations by round 98%.

Caribbean coral

A Cornell College graduate scholar collects a swab pattern from the floor of corals in St. Thomas, U.S. Virgin Islands, in September 2022. Researchers reported {that a} tiny single-celled parasite brought on an enormous 2022 die-off of sea urchins within the Caribbean Sea. (Ian Hewson/Cornell College by way of Alokito Mymensingh 24)

That case was by no means solved. However this time, a global group of researchers jumped into motion, taking samples from sick urchins and wholesome ones throughout the Caribbean to search for genetic clues.

They didn’t see indicators of viruses or micro organism, stated examine writer Ian Hewson, who researches marine ailments at Cornell College. However they did spot traces of tiny single-celled organisms referred to as ciliates, which solely confirmed up within the sick urchins.

Although most ciliates don’t trigger illness, this sort has been linked with different aquatic outbreaks, making it a main suspect, Hewson stated.


To substantiate they’d caught the killer, scientists positioned the parasites in tanks with wholesome urchins grown in captivity to see how they’d react. Out of 10 urchins who have been pitted in opposition to the tiny creatures, 60% of them died — after exhibiting the identical signs researchers have been seeing within the wild.

It is doable that this identical parasite additionally brought on the die-off within the Eighties, however scientists can’t ensure, Breitbart stated.

And so they haven’t found out a option to deal with the diseased urchins. However they’re hopeful that figuring out the supply of the die-offs will assist preserve the reefs, particularly as soon as they be taught extra about how the parasites unfold, Breitbart stated.

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These urchin deaths and different stresses have already remodeled the reefs, added Don Levitan, a marine scientist at Florida State College who was not concerned with the examine.

Again earlier than the primary sea urchin die-off, Levitan recalled seeing reefs within the U.S. Virgin Islands blanketed within the spiny creatures. Now, these reefs look a lot totally different — choked by algae, struck by coral illness and wired from rising temperatures.

“Coral reefs within the Caribbean are in hassle,” Levitan stated. “We’re at a unique place than we have been 30, 40 years in the past.”

Peter Johnson