In recent months, there have fortunately been increased sightings of living young diadem sea urchins (Diadema setosum) in the Red Sea. Although their numbers remain significantly below previous levels – when they could be seen almost everywhere at dusk – these observations offer hope. Diadem sea urchins play a central role in the coral reef ecosystem: acting as "lawnmowers", they graze down algae, thereby preventing them from overgrowing and suffocating the corals.
Regrettably, isolated disease outbreaks have recently been reported again in the northern Red Sea. Particularly concerning is that the small, healthy sea urchins – the beacons of hope for the next generation – disintegrated into skeletons within just 48 hours. We strongly hope that these are locally contained, isolated incidents and will keep you informed of further developments.
Whether the pathology will spread again or remain restricted to a few areas cannot yet be determined. However, one thing is certain: we must monitor the situation closely.
The lethal pathogen – the same one that has already dramatically decimated sea urchin populations in the Mediterranean and the Red Sea – has now also reached the Indian Ocean. It is a ciliate (a single-celled organism) that specifically infects diadem sea urchins and leads to the death of the animals within a very short time.
"Every single observation counts," says marine biologist Prof. Dr. Ralph Schill from the University of Stuttgart and the aquatil research organisation. "This is precisely why the free app Dive4Diadema is so important: it is our early warning system – powered by your vigilance, your dives, and your reports. Thank you very much for being part of this citizen science initiative!"
