Deadly pathogen identified as global threat to coral reefs

Tel Aviv University researchers have identified the pathogen responsible for the mass die-off of sea urchins in the Red Sea, a phenomenon that poses a serious threat to coral reefs around the world. This outbreak spread to the Indian Ocean, presenting a dire warning of a potential global pandemic.

Sea urchins, vital protectors of coral reefs, play a vital role in maintaining ecological balance by feeding on algae that compete with corals for sunlight. The disappearance of these “reef gardeners” can seriously disrupt the fragile ecosystem, potentially leading to widespread degradation of coral reefs.

The Tel Aviv University team, led by Dr. Omri Bronstein of the Steinhardt School of Zoology and Museum of Natural History (SMNH), first identified the phenomenon in Eilat.

The team discovered the waterborne pathogen causing these mass deaths: a scuticociliated parasite similar to Philaster apodigitiformis. This pathogen was also linked to the die-off of sea urchins Diadema antillarum in the Caribbean, which led to a catastrophic phase change in coral reefs in 1983.

“The deadly pathogen is carried by water and can affect large areas in a very short time. Even sea urchins raised in the seawater systems of the Eilat Interuniversity Institute of Marine Sciences or the Underwater Observatory were infected and died after the pathogen entered through the seawater system. recirculating seawater,” Bronstein said.

The epidemic, which appeared in December 2022, decimated sea urchin populations in the Red Sea and spread to the Indian Ocean. Researchers estimate it has killed hundreds of thousands of sea urchins worldwide. The two species of sea urchins once dominant in the Gulf of Eilat have completely disappeared, with similar impacts seen in other regions.

Bronstein and his team used molecular genetics tools to identify the pathogen and documented the progression of the disease. Sea urchins die within two days of infection, leaving behind only bare skeletons, often devoured by predators in the process.

Researchers revealed that the outbreak spread along human transportation routes in the Red Sea. Within weeks, the outbreak spread to Dahab, wiping out sea urchin populations that were once abundant in those areas.

The research highlights the rapid and deadly nature of the epidemic, which led to the almost total disappearance of the affected sea urchin species in certain regions. Bronstein highlights the urgent need to establish broodstock populations in isolated cropping systems in order to preserve endangered species and reintroduce them to their natural habitats in the future.

“We need to understand what caused this outbreak at this time,” Bronstein said. “Is the pathogen unknowingly transported by ship? Or has it always been there, erupting now due to a change in environmental conditions? These are precisely the questions we are currently working on.