EILAT: The Red Sea’s spectacular coral reefs face a new threat, marine biologists warn — the mass death of sea urchins that may be caused by a mystery disease.

Because the long-spined creatures feed on algae that can suffocate corals, their die-off could “destroy our entire coral reef ecosystem”, warned scientist Lisa-Maria Schmidt.

In Israel’s Red Sea resort of Eilat, which borders Jordan and Egypt, Schmidt recalled the moment she and her colleagues first witnessed the population collapse.

“When we jumped into the water, all of a sudden all those specimens we used to see before were gone, and what we saw was skeletons and piles of spines,” she said.

The team had first heard reports in January that a sea urchin species off Eilat was dying rapidly, so they went to a site known for an abundance of the species Diadema setosum. They first thought that local pollution could be to blame.

But, within two weeks, the spiny invertebrates also started dying down the coast, including in a seawater-fed facility of the Inter-University Institute for Marine Sciences. Scrambling to find the cause, the scientists watched with growing alarm as the mass mortality spread south through the Red Sea.

The team found that it affected two kinds of sea urchin, Diadema setosum and Echinothrix calamaris, while other species in the same environment remained unharmed. In the marine reserve off Eilat, colourful fish and some other sea urchin species could be seen by a visiting journalist — although the impact of humans was never far away.

Published in Dawn, September 25th, 2023