Kategorie: News
A citizen science project
For a good year now, the citizen science project Dive4Diadema has been searching for the last surviving diadem urchins in the Red Sea. (We reported on this...). The aim is to find out more about the sudden disappearance of this important sea urchin species, which plays a central role as an algae eater on coral reefs. Diadema urchins eat algae from the corals, creating space for them to grow. You can actively help by using an app to report sightings of the sea urchins.
Recent studies show that, in addition to the well-known Red Sea Diadema urchin (Diadema setosum), other species in the Diadema family are also affected in the Red Sea and western Indian Ocean. This poses a significant threat to the coral reefs of these regions.
The mass extinction of the Red Sea diadem urchin began in July 2022 in the eastern Mediterranean, where the animals had migrated as an invasive species through the Suez Canal. By March 2023, it was estimated that the populations had declined by about 99%. However, in the following months, they have reproduced very successfully and are now so common in many places that they are becoming a serious problem for the native marine life of the Mediterranean.
Shortly after the mass mortality event in the Mediterranean Sea, the first dead Diadem urchins were discovered in the ports of Aqaba and Eilat, and the die-off quickly spread to the southern Red Sea and western Indian Ocean. It is suspected that the pathogen was introduced from the Mediterranean into the Gulf of Aqaba by shipping traffic.
Infection as the cause of the rapid die-off of the sea urchins
The pathogen responsible, a unicellular organism, has now been identified. It kills the sea urchins within 48 hours of infection. The pathogen belongs to the same group of unicellular organisms that have caused similar mass deaths in the Caribbean in recent decades. It is suspected that these unicellular organisms also kill other species in the Diadem urchin family, such as Diadema savignyi, Echinothrix calamaris and Echinothrix diadema, although the pathogen has not yet been detected in these species. Other sea urchin species that do not belong to the Diadem urchin family do not appear to be affected in either the Caribbean or the Red Sea.
Unfortunately, we still know too little about the remaining diadem urchins in the Red Sea. During this year's research, Dive4Diadema found a few live urchins, but they were scattered far and wide across the reef. This makes successful reproduction and natural reintroduction more difficult.
All recreational divers are therefore invited to continue to report their observations during their dives using the free, multilingual ‘Dive4Diadema’ app (see below for more information). Every report, whether of living or dead diadem urchins, helps us to better understand the mass extinction. Not seeing any sea urchins is also valuable information.
A joint campaign by dedicated partners
‘Dive4Diadema’ is a joint initiative of 63 dedicated diving centres, tour operators, diving training organisations, diving equipment manufacturers and scientific institutions. Only by working together can we find the last occurrences of the Red Sea Diadema urchin and record long-term changes. Therefore, a big thank you to everyone who supports the ‘Dive4Diadema’ project and is committed to the preservation of underwater biodiversity.
You can find ‘Dive4Diadema’ and Prof. Dr. Ralph Schill at InterDive from 26 to 29 September in Friedrichshafen at Stand 142. You can find out everything about the Diadem urchin there. Many of the partner companies are also guests at InterDive. Come and visit us!
More information:
Dive4Diadema Homepage
Google Playstore:
Apple App Store
Dive4Diadema - Citizen Science under water