image: Prof. Omri Bronstein
Credit: Tel Aviv University
The mass mortality event was documented in the Canary Islands
Researchers now fear that the pattern observed in the Canary Islands mortality event will also emerge in other regions around the world, where unprecedented mass die-offs of sea urchins have been recorded in recent years.
A global study by an international research team, including Prof. Omri Bronstein of the School of Zoology, Wise Faculty of Life Sciences and the Steinhardt Museum of Natural History at Tel Aviv University - who is leading global efforts to study the wave of sea urchins mass mortalities around the world, presents new and particularly alarming findings: for the first time, evidence of apparent local sea urchin extinction has been found in the Canary Islands.
The study revealed that the genus Diadema (the long-spined black sea urchins many of us are familiar with) is no longer able to produce offspring at this site — a finding that likely indicates local extinction.
The study was carried out by an international consortium including Tel Aviv University scientists in collaboration with researchers from Spain and the Canary Islands. The findings were published in the journal Frontiers in Marine Science.
Prof. Bronstein describes the sequence of events over recent decades: “In 1983–84, a mass mortality event of Diadema sea urchins was recorded in the Caribbean islands in the western Atlantic Ocean. This die-off triggered a dramatic ecological shift in the region: with the sea urchins — the habitat’s primary algae grazers — gone, vast algal fields spread, blocking sunlight and causing severe, irreversible damage to coral reefs in the region. In 2022, another mortality event struck the Caribbean, and for the first time the pathogen responsible for the lethal disease was identified. This epidemic spread to the Red Sea by 2023, and by 2024 it was also detected in the Western Indian Ocean, off the coast of Reunion.”
In the current study, a formerly undetected mass mortality event was identified in the Canary Islands, off the coast of Morocco in the eastern Atlantic Ocean, which in fact occurred as early as mid-2022. According to the researchers, this event represents the “missing link” in the disease’s geographic spread. The study also revealed a particularly troubling finding, which likely points to the potential local extinction of the species in the Canary Islands. The study was based on extensive observational data collected through local citizen science, alongside scientific surveys, satellite data analysis (remote sensing), and the collection of samples from the seafloor by the research team.
Prof. Bronstein explains: “Sea urchins reproduce by releasing sperm and eggs into the seawater, where fertilization produces millions of embryos that drift as plankton in the water column. After several days to weeks (depending on the species), the larvae settle on the seabed and develop into juvenile urchins — a process known as ‘recruitment.’ In this study, we discovered that for the first time in history, there are no new juvenile urchins being recruited across several Canary Islands, indicating that the recruitment process has halted since the extensive mortality event that took place there. In other words, the die-off of the adult urchins has been so widespread that the species is no longer able to produce a next generation, if no recruitment occurs, the species may disappear from the region’s ecosystem.”
The researchers note that sea urchin populations are typically characterized by fluctuations — they often decline and later recover. This time, however, the situation is far more severe and appears to be an extinction event rather than a transitional phase. The researchers warn that the pattern observed in the Canary Islands may also unfold in other regions around the world where unprecedented sea urchin mass mortality events have been recorded in recent years — including the Red Sea coast and the coral reef of the Gulf of Eilat.
Prof. Bronstein concludes: “In this study, we identified a mass mortality event of sea urchins that occurred in mid-2022 in the Canary Islands. In its aftermath, it became clear that the affected species is no longer capable of successfully reproducing in this area — a finding that may lead to local extinction, which is expected to have severe ecological consequences. A likely outcome would be the uncontrolled proliferation of algae, which would affect the entire ecosystem — although at this stage, it is difficult to predict exactly in what way.
Link to the article:
https://www.frontiersin.org/journals/marine-science/articles/10.3389/fmars.2025.1665504/full
Journal
Frontiers