Thousands of sea urchins have mysteriously washed up dead on a French island in the Indian Ocean, leaving scientists perplexed.
Around 5,000 urchins have washed up on the western side of Reunion Island in the Seychelles since July this year, French news outlet Le Parisien reported.
Scientists have been looking into the cause of these mass deaths, and some theories have been posited, including one laying the blame on a parasite that has previously caused mass die-offs.
Biologist Jean-Pascal Quod said it may be due to a parasite called a philaster—as it has recently been detected on the island for the first time ever.
"[It is] the most probable hypothesis to explain this excess mortality," Quod told Le Parisien. "But until we have done the molecular biology work, we will not be able to guarantee that it is indeed this parasite which is mainly responsible for these deaths."
Although it is the first time this parasite has been detected on or around Reunion, it has been identified in other parts of the world and has been linked to notable mass sea urchin die-offs in the Caribbean and off the coast of Israel in the Mediterranean.
The paradise affects the sea urchin's immune system, leading to them losing their spines and suction and eventually causing them to die.
"[It] endangers the immunity of the sea urchin by causing a disruption of its physiology. We currently do not know how the parasite arrived on the island; it could come from the emptying of boat water tanks, from algae, from microplastics," Quod said. "No solution exists to combat it. We will have to accept this pathology, the sea urchins will have to adapt."
In April, marine biologists in Florida determined that philasters caused the deaths of thousands of sea urchins off the U.S. coast.
Scientists said that the parasite was responsible for killing 98 percent of the sea urchins in the region in the 1980s, The Guardian reported. Although there are no samples from this period to study, the die-offs present similarities with those being reported this year.
Sea urchins are crucial to marine ecosystems and coral reefs, meaning these deaths could pose a more wide-reaching problem. Urchins consume algae and without them reefs can become clogged and starved of nutrients, exacerbating their already fragile state.
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Robyn White is a Newsweek Nature Reporter based in London, UK. Her focus is reporting on wildlife, science and the ... Read more
