The plague that destroyed the sea urchins in Eilat has spread to the Indian Ocean and threatens to destroy sea urchin populations all over the world
Follow-up research by Tel Aviv University reveals that the deadly plague which was revealed last year And which destroyed the sea urchins in Eilat, spread along the Red Sea and also slipped into the Indian Ocean. According to the researchers, what initially seemed like a serious but local epidemic, spread very quickly into a regional epidemic and now appears to be a global epidemic. The sea urchins are considered the "gardeners" of the coral reefs, they feed on the algae that compete with the corals and threaten them, and their destruction could cause severe damage to the coral reefs around the world.
How did the sea urchin population disappear from Eilat Bay?
The research was conducted under the leadership of Dr. Omri Bronstein from the School of Zoology in the George S. Wise Faculty of Life Sciences and the Steinhardt Museum of Nature at Tel Aviv University, and research students Lehan Roth, Gal Avitar, Lisa Schmidt and Mai Bonomo. In addition, an international team of partners, including researchers from the countries of the region and Europe took part in a study that covered thousands of kilometers of coral reefs. The alarming findings were published in the prestigious journal Current Biology.
The researchers estimate that since December 2022, the date when the epidemic broke out in the Gulf of Eilat, most of the populations of the sea urchin species affected by the disease in the Red Sea and an unknown number, estimated at hundreds of thousands, of sea urchins all over the world have been eliminated. They also point out that since the discovery of the plague in the coral reef in Eilat - the two species that were until then the most common in the Gulf have completely disappeared.
Who will protect the 'gardeners' of the coral reef?
As part of the follow-up study, the team of researchers from Tel Aviv University identified with the help of molecular-genetic tools the pathogen responsible for the mass mortality of sea urchins (of the species Diadema setosum) in the Red Sea: a ciliate pathogen of the Scuticociliate type. The researchers explain that this is the same single-celled parasite that was found responsible for the mass mortality of the sea urchin populations in the Caribbean about two years ago and which led to the collapse of the coral reef there.
As stated in December 2022, Dr. Bronstein was the first researcher to detect a mass death of sea urchins of the long-spined nazrite type, those black sea urchins with long spines that were common in the northern Gulf of Eilat, Jordan and Sinai. In addition, Dr. Bronstein and his team discovered for the first time that the plague is also deadly For other related species, following the outbreak of the plague, thousands of hedgehogs died a quick and violent death - within two days Healthy became a skeleton without tissue. As a result, most of the urchins were killed while they were dying and unable to defend themselves. According to estimates, only a few individuals of urchins remain in the coral reef in Eilat.
Dr. Bronstein explains that sea urchins in general, and the long-spined urchin in particular, are considered key species that are essential for the healthy functioning of the coral reef. They are the 'gardeners' of the reef - they feed on the algae and prevent them from taking over and 'suffocating' the corals that compete with them for sunlight.
According to Dr. Bronstein, the most significant and studied mass mortality to date occurred in 1983, when a mysterious disease that spread in the Caribbean wiped out most of the sea urchins of the species Diadema antillarum - relatives of the sea urchins from Eilat. As a result, the algae spread uncontrollably, hiding the corals from light The sun and the entire reef has undergone a change from coral reef to algae fields as well, even though it has died The largest one in the Caribbean occurred already 40 years ago, the population of sea urchins and with them the coral reefs there did not return to their previous state and repeated mortality events were observed throughout the years.
In 2022, the disease returned and broke out in the Caribbean, affecting populations and surviving individuals, but this time the researchers had the scientific and technological tools to decipher the forensic evidence, and a group of researchers from Cornell University successfully identified the cause of death as a pathogenic parasite from the ciliate family.
From a local epidemic to a deadly global epidemic
"This is an ecological disaster of the first order that threatens the population of sea urchins all over the world," says Dr. Bronstein and emphasizes: "It turns out that the mass mortality that we detected in Eilat in 2023 has spread along the Red Sea and even beyond it, in Oman, and it is even hitting Reunion Island these days in the Indian Ocean".
According to him, it is a deadly water-borne pathogen that can infect large areas in a very short period of time. Even urchins raised in seawater systems for research purposes at the Inter-University Institute in Eilat, or in the underwater observatory, were infected and died, because the pathogen was able to enter through the pumping systems.
"The underwater spectacle is almost surreal: to see a species that was so dominant in a certain environment simply wiped out in a period of hours. The thousands of skeletons that roll on the bottom disintegrate and disappear in a very short period of time, so even evidence of what happened is very difficult to find"
"Death, as mentioned, is quick and violent. Our research team was able to record for the first time all the stages of the disease, from the moment of infection to the expected death, in unique systems set up at the Inter-University Institute in Eilat. Also, our work witnesses knew of one species of sea urchin that was affected of this pathogen - the Caribbean species, and one could perhaps hope that even if the damage is severe, nature will find compensation mechanisms such as, for example, an increase in the populations of species Other urchins. Unfortunately, in the new study we show that even related species, such as the species that exists in the Red Sea, and even other species from the same family, are exposed and susceptible to the disease," adds Dr. Bronstein.
Another interesting finding that emerged from the current study shows that the progress of the plague goes through the axis of human movement. "Already when publishing our report last year, we knew about deaths occurring in Aqaba, but we still haven't detected signs of deaths in Sinai. The first point where the deaths appeared in Sinai was near the small port in Nuaiba, which is reached by ferries from Aqaba in Jordan. Two weeks later the plague had already spread to Dahab. The underwater spectacle is almost surreal: to see a species that was so dominant in a particular environment simply wiped out in a matter of hours. The thousands of skeletons that roll on the bottom disintegrate and disappear in a very short period of time, so even evidence of what happened is very difficult to find."
According to Dr. Bronstein, there is currently no way to help the infected sea urchins or to immunize them against the disease, but breeding nuclei of species at risk must be quickly established in breeding systems completely isolated from the sea, so that in the future we can return them to the wild.
"Unfortunately, we have no way to fix nature, but we can definitely fix ourselves. First and foremost, we need to understand what caused this outbreak now? Is it an accidental transfer of the pathogen by a vessel? Or has the pathogen always been here, and just a change in environmental conditions Made him explode? These are the exact questions we are working on these days.'
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