Researchers from Tel Aviv University report a striking epidemic sweeping the Red Sea, erasing an entire sea urchin species from the region. The outbreak not only takes away a key herbivore from the reef but also threatens coral vitality and the broader balance of the ecosystem. The findings are published in Royal Society Open Science.
Sea urchins graze on algae on coral reefs. Their feeding helps regulate algal growth, shielding coral communities. When urchin numbers decline, algae can spread rapidly, crowding out corals and weakening the reef structure. If urchin populations fall unchecked, corals become vulnerable to algae overgrowth, leading to a cascade of biodiversity loss and reduced reef resilience.
In the Gulf of Aqaba at the northern tip of the Red Sea, thousands of Black sea urchins (Diadema cetosum) historically kept algae in check and supported coral health. In a short time, these populations collapsed, leaving behind only skeletal remains as tissue was consumed by an unknown pathogen. Scientists observed that a once-healthy urchin could deteriorate into a skeletal form with extensive tissue damage in as little as 48 hours.
The outbreak now appears to be spreading beyond the Red Sea. Earlier this year, researchers detected early signs of illness among porcupines in the Mediterranean, with initial cases around Greece and Turkey. From there, the disease seems to have moved south through the Suez Canal toward the Red Sea, suggesting a broader geographic footprint that concerns multiple reef systems.
Experts suspect a pathogenic ciliate parasite, a single‑celled organism long linked to mass urchin die-offs. The pattern echoes a notorious event in 1983 when a Caribbean urchin population collapsed, raising concerns about possible global connections and shared vulnerabilities among sea urchin species across oceans. The exact cause remains under investigation, but the parasite’s rapid action highlights a need for swift scientific clarification and monitoring.
The implications extend well beyond the loss of one species. Coral reefs depend on a complex network of interactions among corals, algae, invertebrates, and fish. The disappearance of urchins disrupts this balance, speeding algae growth and threatening reef regeneration. Without swift action, regions with depleted urchin populations risk weaker coastal protection, reduced biodiversity, and disrupted fisheries that rely on reef ecosystems for income and food security.
Researchers urge immediate steps to prevent further extinction of sea urchin populations in both the Red Sea and the Mediterranean. Proposed measures include establishing breeding populations of disease‑free urchins, initiating disease surveillance, and developing biosecurity protocols to prevent further spread. In the longer term, restoration strategies could involve reintroducing healthy urchins after the epidemic subsides, with careful monitoring to ensure successful establishment and ecological balance.
Scientists call for collaboration among regional governments, research institutions, and conservation groups to track the pathogen, quantify ecological impacts, and implement containment measures. Enhanced underwater monitoring, sample collection, and rapid data sharing will be crucial to understanding the disease trajectory and guiding effective responses. The study underscores the delicate balance of reef ecosystems and the vulnerability of key species to emerging pathogens in the context of changing ocean conditions.
Ultimately, the Red Sea and Mediterranean face a shared challenge: safeguarding their reef ecosystems by preventing further urchin losses, supporting reef recovery, and protecting coastal communities that depend on these vibrant habitats for livelihoods, tourism, and natural protection from storms. Ongoing research aims to establish a robust framework for responding to similar outbreaks in the future, prioritizing early detection, rapid response, and resilient restoration strategies [citation: Royal Society Open Science].