The main causes of mass mortality occasions in sea urchins are pathogens, storms, and excessive temperatures

Meta-Analysis of All Scientific Literature within the Field Finds:

The Leading Causes of Mass Mortality Events in Sea Urchins are Pathogens, Storms, and Extreme Temperatures

• Underwater “COVID” Test: In an extra examine, the analysis workforce developed a brand new, cheap, and non-invasive methodology for underwater genetic sampling utilizing a swab – just like a COVID-19 take a look at.

Two pioneering research by researchers from the School of Zoology and the Steinhardt Museum of Natural History at Tel Aviv University, led by Dr. Omri Bronstein, have recognized the first drivers of sea urchin mass mortality occasions over current many years: pathogens, storms, and excessive temperatures. In addition, Dr. Bronstein and his workforce have developed an revolutionary methodology for genetic sampling in marine environments – utilizing a swab just like a COVID-19 take a look at,  to allow fast and non-invasive monitoring of marine animals and underwater illness outbreaks.

The first examine, printed within the journal Biological Reviews, presents a meta-analysis of all 110 scientifically documented mass mortality occasions (MMEs) amongst sea urchins recorded between 1888 and 2024. Dr. Bronstein and PhD scholar Lisa Schmidt carried out a complete assessment of the historical past of those occasions, exhibiting that almost all reported MMEs originate within the Northern Hemisphere, notably within the United States, Western Europe, and Japan, the place nearly all of analysis and funding are concentrated. The Tel Aviv University researchers labeled 5 primary causes of those occasions and located that 33% have been brought on by pathogens, 25% by catastrophic occasions corresponding to storms and oxygen depletion, 24% by excessive temperatures, 11% by algal blooms, and seven% by human exercise, corresponding to air pollution and habitat destruction.

“This is a meta-analysis of all scientific literature on the subject,” says Dr. Bronstein. “For each mass mortality event, we mapped where and when it occurred, which species were affected, and most importantly — what the causes were. After filtering out hundreds of publications who lacked sufficient credible data to be included in our analyses, ee found that pathogens are the leading cause of mass mortalities among sea urchins. This finding aligns closely with what we are seeing today in the modern wave of die-offs — from the Caribbean to the Red Sea and the Indian Ocean. There is a tendency to attribute everything to global warming, but that is not always accurate. In many cases, mortality is not directly related to heat, as some affected sea urchin species naturally live in even warmer environments. These temperatures may not be optimal, but they are not lethal for these species. The problem is that warming influences many other environmental factors, which can combine into a deadly mix. For example, warmer waters tend to have lower dissolved oxygen and higher pathogen activity.”

In 2023, Dr. Bronstein recognized a mass mortality occasion of long-spined sea urchins (Diadema setosum) alongside the Red Sea coast. He subsequently discovered that the identical pathogen,  a ciliate parasite, accountable for wiping out a associated Caribbean species was additionally responsible. Since that discovery, the outbreak has unfold to the Indian Ocean, reappeared within the Caribbean, and is now thought of a worldwide pandemic threatening sea urchin populations worldwide.

“Sea urchins are vital to coral reef health,” explains Dr. Bronstein. “They are the ‘gardeners’ of the reef: they feed on algae and prevent it from overgrowing and suffocating the corals competing for sunlight. In 1983, the most dominant Caribbean Sea urchin species, Diadema antillarum, died in vast numbers from an unknown reason at the time; algae proliferated uncontrollably, shaded the corals, and the entire ecosystem shifted from coral reefs to algal fields. Even 40 years later, the sea urchin population — and the reefs — have not recovered. We fear that the same process may now occur in other parts of the world where mass die-offs are happening, mainly among the long-spined sea urchin, a relative of the Caribbean species — the black urchin with long spines familiar to everyone. Until recently, it was one of the most common reef urchins in Eilat; today it has almost disappeared from large parts of the Red Sea. This is a very violent event: within less than 48 hours, a healthy population turns into disintegrating skeletons. In some sites in Eilat and Sinai, mortality reached 100%. Later, mass deaths were recorded on Réunion Island in the Indian Ocean, and we are now investigating three additional mass mortality events in the Atlantic and Indian Ocean, and even the Mediterranean Seas. What began as a local mortality event has become regional and then global, posing a threat to coral reefs everywhere.”

To handle one of many main challenges in marine genetic sampling, graduate scholar Mai Bonomo and Dr. Bronstein printed a separate examine in Molecular Ecology Resources, creating a brand new, cheap, and non-invasive methodology for accumulating underwater genetic samples at scale.

“The main tools used today to identify both animals and pathogens are genetic,” says Dr. Bronstein. “But molecular ecology faces a fundamental problem: there’s no simple way to sample DNA from live marine animals underwater. As a result, many studies rely on invasive methods that harm the animal or even require sacrificing it completely to bring it into the lab. Therefore, research in this field is heavily regulated, weighing each case’s scientific value against environmental ethics. For example, sampling is prohibited in marine nature reserves, there are restrictions and bans on shipping samples abroad, including corals and every scientific publication must present the official permits for each sample it reports. Our need to overcome this bottleneck arose from the sea urchin pandemic. Today, there are only two ways to detect diseased urchins: visually, which is too late, as the animals are already dying, or through genetic tools that can detect disease before symptoms appear. But if detecting disease requires removing the animal from the sea, it makes no difference whether it’s sick or not, we end up sacrificing it.”

To overcome this problem, Tel Aviv University researchers developed a specialised underwater genetic sampling equipment that’s sturdy, dependable, cheap, and simple to make use of and it’s already being adopted by analysis teams worldwide, particularly in distant or delicate areas.

“We developed a new tool for underwater DNA sampling that resembles a COVID-19 test,” explains Dr. Bronstein. “At the tip of a particular tube crammed with a preservation liquid is a membrane stopping water penetration, sealed with a clip-cap — very similar to some toothpaste tubes. Just like a COVID take a look at, the researcher gently swabs the floor of the marine animal, with out harming or shifting it. There’s no want to gather mucus as in people — only a mild swipe is sufficient. The swab is then inserted into the tube, piercing the membrane that protects the preservation liquid inside, and the cap is locked to safe the pattern. That’s it. A single researcher can acquire dozens of samples in a single dive, beneath virtually any environmental or depth situations.

 

The equipment has already been examined in difficult environments, together with subject expeditions to Djibouti and Réunion Island, and the outcomes are very promising: samples remained exceptionally well-preserved for months with out refrigeration earlier than arriving at our lab, and nonetheless allowed for delicate genetic analyses. In a large-scale trial we carried out within the Gulf of Eilat, we collected genetic materials from lots of of echinoderms, the group that features sea urchins and starfish, inside only a few months and carried out probably the most intensive genetic evaluation ever carried out on these species within the area. This led to the invention of a number of new species and the reclassification of others beforehand unknown to science. This is an easy and chic answer to one of the persistent technical challenges in marine molecular ecology.”

Links to the articles:

Biological Reviews

Molecular Ecology Resources

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