A marine microorganism believed to have originated in the Caribbean is causing mass die-offs of sea urchins in the Red Sea and Indian Ocean and threatens to spread across the planet, a new study warns. Because sea urchins play an important role in the health of coral reefs, a “pandemic” could have serious consequences.
a ciliate protozoan belonging to the parasitic genus Philasterkills all sea urchins it infects within days, Israeli researchers report in a review Current Biology.
The same microorganism probably caused the mass kill of sea urchins of the species Hairy diadem In the Aegean in 2022.
This particular species of sea urchin, which has 30 cm long venomous stings, is an alien species in the Mediterranean, as it comes from the Red Sea.
Thousands of dead sea urchins washed up on Reunion Island in the Indian Ocean last year (Jean-Pascal Quod)
The Hairy diadem It is endemic to the Red Sea, where the outbreak began in late 2022, first in the Gulf of Aqaba and then south along the coast of the Sinai Peninsula in Egypt. Then it reached Reunion Island near Madagascar in the Indian Ocean.
Except for hedgehogs of the genus Diademthe parasite has also been found to attack a related genus Echinothrixwhich increases the potential impact.
The spread in the Indian Ocean is now a concern as the protozoan moves eastward to the tropical waters of the Coral Triangle in Asia and the Great Barrier Reef in Australia.
The poisonous sea urchin Diadema setosum is an alien species in the Mediterranean Sea (Wikimedia Commons)
Sea urchins are important for protecting corals, he said Reuters o Omri Bronstein, a zoologist at Tel Aviv University. He described sea urchins as “lawn mowers” because they eat algae that would otherwise cover corals and deprive them of light.
Algae in the Gulf of Aqaba has already started to multiply, he said.
“When the mass die-offs started in the Red Sea, it was so sudden and violent that our first thought was that it was some kind of pollution or something else very serious but very localized,” he said.
It remains unknown how the parasite was spread, but suspicions point to ships’ ballast water, as cases outside the Sinai have emerged near a port that receives ferries north from the Jordanian city of Aqaba.