Ocean's “ecosystem engineers” vanish in simultaneous die-offs across Caribbean, Mediterranean, and Indian Oceans
By isabelle // 2025-12-18
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  • A mysterious pandemic is devastating vital sea urchin populations globally.
  • In the Canary Islands, some sea urchin populations have collapsed by over 99%.
  • These urchins are crucial grazers that keep algae in check and support healthy reefs.
  • The die-off has triggered a reproductive collapse, preventing natural recovery.
  • The unidentified pathogen threatens marine ecosystems and the human communities that depend on them.
A quiet catastrophe is unfolding beneath the ocean’s surface, and it's one that threatens to unravel the delicate balance of marine ecosystems worldwide. Since 2022, a mysterious and lethal disease has swept through populations of a vital sea creature, the long-spined sea urchin, pushing some to the very edge of extinction. The alarming spread of this marine pandemic, documented in a new study, highlights a fragile ocean system in crisis and poses serious questions about the future health of our seas and the human communities that depend on them. The focus of this ecological disaster is the sea urchin Diadema africanum in the Canary Islands. Research led by Iván Cano, a doctoral student at the University of La Laguna, reveals a population in freefall. Surveys show a devastating 74% decrease in La Palma and a near-total 99.7% collapse in Tenerife since 2021. "Our analyses showed that the current abundance of D. africanum across the Canary Islands is at an all-time low, with several populations nearing local extinction," said Cano.

A global pattern emerges

This is not an isolated incident. "At approximately the same time, other Diadema species have been observed to be dying off in the Caribbean, the Mediterranean, the Red Sea, the Sea of Oman, and the western Indian Ocean," Cano explained. The simultaneous global scale indicates a widespread marine pandemic targeting these key grazers. The pathogen responsible remains unidentified, though similar die-offs have been linked to parasitic single-celled organisms like ciliates or amoebae. The historical context makes this latest event particularly dire. Similar mass mortality struck the region in 2008 and 2018, but populations showed a capacity for rapid rebound. The 2022-2023 outbreak is different. It was followed by a second wave in 2023, and crucially, the sea urchins have essentially stopped reproducing. Research found negligible numbers of larvae and no early juveniles on the eastern coast of Tenerife, signaling a reproductive collapse that threatens any natural recovery.

Why sea urchins are indispensable

To understand the gravity of this loss, one must recognize the sea urchin’s role as an ecosystem engineer. Like large grazers on land, these spiny creatures constantly feed on seaweed and seagrass. This grazing is essential; it controls fast-growing algae, clearing space for slow-growing, foundational species like corals and calcifying algae to thrive. In this way, healthy urchin populations help maintain biodiverse and productive rocky reefs. The concern for humanity is direct and profound. Coral reefs and healthy algal forests support immense fisheries, protect coastlines from storm surges, and drive tourism economies. A loss of the urchins that help maintain these systems can trigger a cascade of degradation. As algae grow unchecked, they can smother corals, reduce habitat complexity for fish, and fundamentally alter the food web. The study authors warn of "serious consequences for these key reef grazers." The source of the pandemic remains a troubling mystery. "Without a confirmed identification, we cannot say whether the agent arrived from the Caribbean by currents or shipping, or whether climate change is to blame," Cano stated. This uncertainty hampers the global response. Furthermore, the initial population boom of these urchins was likely fueled by the overfishing of their natural predators, demonstrating how easily our actions disrupt oceanic equilibrium. While some Diadema populations in Southeast Asia and Australia remain unaffected for now, scientists are on alert. "We aren't yet sure how this pandemic will evolve," Cano cautioned. The precarious state of the Canary Islands populations serves as a warning. The near-total silence from the seafloor where these urchins once thrived is a quiet alarm bell. It signals a broken link in a chain that supports the ocean's vitality, a reminder that the most critical threats often remain hidden beneath the surface until their effects are irreversible. The health of our oceans, and by extension our own future, may depend on solving this aquatic mystery before it is too late. Sources for this article include: ScienceDaily.com FrontiersIn.org TheGuardian.com Earth.com
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