A deadly pathogen responsible for the mass die-off of sea urchins in the Red Sea has spread to the Indian Ocean, potentially endangering vital coral reef ecosystems worldwide, Israeli researchers warned on Tuesday.

“This is a first-rate ecological disaster. Sea urchins are vital to the health of coral reefs. They act as the ‘gardeners’ of the reef by feeding on algae, preventing it from overgrowing and suffocating the coral, which competes with algae for sunlight,” said Dr. Omri Bronstein of Tel Aviv University who is leading an international research team tracking the sea urchin pandemic.

Originating from the Red Sea and previously devastating sea urchin populations in the Caribbean, the pathogen, a highly aggressive ciliate parasite, poses a global risk.

Coral reefs act as nurseries and habitats for countless marine species, providing shelter, food, and protection from predators. They also serve as a natural barrier, reducing coastal erosion and buffering against storm damage. Coral reefs also trap carbon that would otherwise be released into the atmosphere, helping mitigate the impact of climate change.

The findings, published in the peer-reviewed journal Ecology, confirm that the same pathogen has caused catastrophic mortality events in sea urchin populations from the Red Sea to Réunion Island in the Indian Ocean. Bronstein describes the situation as “a first-rate ecological disaster,” noting that mortality rates in affected areas exceed 90%, with some sites experiencing total population collapse.

Within two days of contracting the parasite, a healthy sea urchin becomes a skeleton with massive tissue loss. While some corpses are washed ashore, most sea urchins are devoured while they are dying and unable to defend themselves, which could speed up contagion spread by the fish who prey on them.

Historical parallels add to the urgency. In 1983, a mysterious disease wiped out most Diadema sea urchins in the Caribbean, shifting the region from a coral-dominated ecosystem to an algae-dominated one. When the pathogen reappeared in the Caribbean in 2022, researchers identified the culprit as a Scuticociliate parasite. By 2023, the disease had spread to the Red Sea, where Bronstein reported mass die-offs among long-spined sea urchins within just 48 hours.

Recent genetic analyses by the researchers confirm that the same pathogen is responsible for similar events in the Indian Ocean.

“Now it’s a global event, a pandemic,” he warned. While the Pacific Ocean remains unaffected for now, the team is actively investigating potential risks, as the region hosts some of the largest and most biodiverse coral reefs in the world.

Monitoring these outbreaks is fraught with challenges. The vastness and remoteness of underwater environments mean that many mortality events might go unnoticed. “If we miss the mortality event by even a couple of days, we might find no trace of the extinct population,” Bronstein explained.

The researchers have developed two hypotheses to explain the pathogen’s spread. One suggests the pathogen traveled in the ballast water of cargo ships. The other suggests that rising sea temperatures and changing marine environments have made the pathogen more virulent.

“There is no Pfizer or Moderna for sea urchins,” said Bronstein.

Efforts are instead focused on prevention, early detection, and breeding programs to ensure the survival of unaffected populations.

In collaboration with the Israel Aquarium in Jerusalem, Bronstein has established a breeding nucleus for Red Sea sea urchins. This controlled environment, isolated from seawater, allows researchers to study the species and develop genetic tools for early disease detection. The aim is to create a reliable reserve population for future reef restoration efforts.

These efforts parallel the development of “underwater COVID tests” for sea urchins, which would enable early identification of the pathogen in seawater samples.

Said Bronstein, “We are racing against time to understand and contain this pandemic before it reaches even more of the world’s reefs.”