An infectious agent that causes disease in sharks and fish attacks sea urchins, causing a deadly wave that is rapidly spreading globally
Since the end of 2022, sea urchins have been dying en masse in the northern Gulf, near Aqaba, Jordan. “It’s surreal and horrible. “You are swimming through piles of dead sea urchins,” comments Omri Bronstein, a marine biologist at Tel Aviv University, who began research into this strange mortality in February 2023 in the journal Science.
In less than two months, had already reached the Sinai Peninsula, Egypt. “The progression of symptoms appears rapid, causing death within two days,” explains the researcher’s team in “Royal Society Open Science”. Above all, the cause of this disease is quite mysterious. None of those known to cause sea urchin deaths seem to match.
Ian Hewson, an oceanographer from Cornell University, and his team managed to identify the agent responsible for this deadly wave: the scuticocilia. A single-celled organism originally known to cause various diseases in sharks, fish or crustaceans. The first cases of disease came from Caribbean waters. One hypothesis is that the organism clung to the hulls of boats, which would explain why the disease then reached the Red Sea and Greece within a few months.
However, researchers do not know how the disease eventually spread to sea urchins and whether this transmission « was influenced by changes in environmental conditions. »
Threat to coral reefs
However, once infected by this organism, sea urchins become immobile, which makes them more vulnerable to predators. However, being herbivores, they help control the algae population.
READ ALSO
Certain lark hunts deemed illegal by the Council of State
High tides and bad weather: water rose in the South-West, an octogenarian, sixth victim in Hérault
Too many algae prevent light rays from reaching the seabed, which are vital for corals. This is why this mortality of sea urchins also represents a threat to coral reefs and the organisms they shelter, already in danger due to intensive fishing and rising water temperatures.
