Two groundbreaking studies from Tel Aviv University have shed light on the alarming mass mortality events of sea urchins, identifying primary drivers such as pathogens, storms, and extreme temperatures. Led by Dr. Omri Bronstein, researchers from the School of Zoology and the Steinhardt Museum of Natural History have also pioneered a novel method for genetic sampling in marine environments, offering a non-invasive approach akin to a COVID-19 swab test.
The first study, published in Biological Reviews, provides a comprehensive meta-analysis of 110 scientifically documented mass mortality events (MMEs) among sea urchins from 1888 to 2024. Dr. Bronstein and PhD student Lisa Schmidt found that the majority of these events occurred in the Northern Hemisphere, particularly in the United States, Western Europe, and Japan, where research and funding are most concentrated. The study classified the causes of these events, revealing that 33% were due to pathogens, 25% to catastrophic events like storms and oxygen depletion, 24% to extreme temperatures, 11% to algal blooms, and 7% to human activities such as 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.”
Understanding the Global Sea Urchin Pandemic
In 2023, Dr. Bronstein identified a mass mortality event of long-spined sea urchins (Diadema setosum) along the Red Sea coast, attributing it to a ciliate parasite also responsible for a similar event in the Caribbean. This pathogen has since spread to the Indian Ocean and reappeared in the Caribbean, marking a global pandemic threatening sea urchin populations worldwide.
Sea urchins play a crucial role in maintaining coral reef health by feeding on algae and preventing it from overgrowing and suffocating corals. Dr. Bronstein warns that the current wave of die-offs could lead to ecological shifts similar to the 1983 event when the Caribbean sea urchin population collapsed, resulting in algal dominance over coral reefs.
“Sea urchins are vital to coral reef health,” explains Dr. Bronstein. “They are the ‘gardeners’ of the reef.”
Mass die-offs have been recorded in regions such as Eilat and Sinai, with mortality rates reaching 100% in some areas. The phenomenon has escalated to a global scale, posing a significant threat to coral reefs across the Atlantic, Indian Ocean, and even the Mediterranean Seas.
Innovations in Marine Genetic Sampling
Addressing the challenges of marine genetic sampling, graduate student Mai Bonomo and Dr. Bronstein have developed a new, non-invasive method for collecting underwater genetic samples. This method is detailed in a separate study published in Molecular Ecology Resources.
“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.”
The innovative sampling kit, already adopted by research groups worldwide, allows for rapid and non-invasive collection of genetic material. It resembles a COVID-19 test, where researchers gently swab the surface of the marine animal without causing harm. This method has proven effective in various challenging environments, preserving samples for months without refrigeration.
A Simple New Tool for Rapid, Non-Invasive Sampling
The Tel Aviv University team has successfully tested the kit in locations such as Djibouti and Réunion Island, achieving promising results. In a large-scale trial in the Gulf of Eilat, they collected genetic material from hundreds of echinoderms, leading to the discovery of new species and the reclassification of others.
“We developed a new tool for underwater DNA sampling that resembles a COVID-19 test,” explains Dr. Bronstein. “A single researcher can collect dozens of samples in one dive, under almost any environmental or depth conditions.”
Implications and Future Directions
The findings from these studies highlight the urgent need for global awareness and action to protect sea urchin populations and, by extension, coral reef ecosystems. The innovative genetic sampling method offers a promising tool for ongoing monitoring and research, potentially aiding in the early detection of disease outbreaks and the preservation of marine biodiversity.
As the global sea urchin pandemic continues to unfold, researchers and conservationists are called to collaborate in mitigating the impacts of these mass mortality events. The development of non-invasive sampling techniques represents a significant step forward in marine conservation, offering hope for the future of coral reefs and the diverse life they support.
