Mass mortality of the invasive alien echinoid Diadema setosum (Echinoidea: Diadematidae) in the Mediterranean Sea

Abstract

The sea urchin Diadema setosum is an ecological key species across its range, particularly on coral reefs. In 2006 D. setosum was first observed in the Mediterranean Sea, and since, it has proliferated to occupy the entire Levantine Basin. Here we report the mass mortality of the invasive D. setosum in the Mediterranean Sea. This is the first report of D. setosum mass mortality. The mortality spans over 1000 km along the Levantine coast of Greece and Turkey. The current mortality shows similar pathologies to previously reported Diadema mass mortality events, suggesting pathogenic infection as the cause of mortalities. Maritime transport, local currents, and fish predation of infected individuals may distribute pathogens at varying geographical scales. Due to the proximity of the Levantine Basin to the Red Sea, the risk of pathogen transport to the native Red Sea D. setosum population is imminent—with potentially catastrophic consequences.

The last observation of the long-spined exotic Sea Urchin (Diadema setosum) in the Gulf of Antalya

“…Mass mortality incidents can occur on sea urchins. The best example of this is the collapse of the Diadema antillarum population in the Caribbean and Western Atlantic, as found in our literature research (Hewson et al 2023;Zirler et al 2023). It has been reported that this species experienced recurring mass mortalities in the 1980s and 2022.…”

“…These mass mortalities are reported to be caused by a pathogen (Philaster apodigitiformis). Similarly, mass mortality events were observed in Diadema africanum populations in the Eastern Atlantic in 2009 (Zirler et al, 2023). It is reported that Vibrio alginolyticus, which increases due to abnormally rising water temperatures, is responsible for these mortalities (Clemente et al, 2020).…”

“…observed in the coastal waters of Monsef town along the Lebanese coast (Nader & El Indary 2011), and in 2010, it was observed in the Gulf of Iskenderun, Yayladağı, on the southeastern coast of Turkey (Turan et al 2011). After these reports, D. setosum rapidly proliferated in the Mediterranean and expanded its distribution along the coasts of Turkey, Greece, Lebanon, Israel, Egypt, and Libya (Zirler et al, 2023). D. setosum, which can be observed up to a depth of 2-3 meters in rocky and stony areas with wave action, has also started to pose a risk for local people.…”

Ecological baselines in the Eastern Mediterranean Sea shifted long before the availability of observational time series

“…However, their predicted effects do not fit the patterns observed in our dataset. Diseases can cause mass mortalities in both native species and NIS (e.g., García‐March et al., 2020; Katsanevakis et al., 2019; Zirler et al., 2023), but affect only one or a few taxa at a time, rather than an entire, highly diverse phylum (Fey et al., 2015). Pollution events, while potentially impacting multiple taxa, are limited in their spatial extent, whereas molluscan density declined simultaneously at six stations spanning almost the entire Israeli coastline.…”

Design and validation of a PCR protocol to specifically detect the clade ofPhilastersp. associated withDiadema antillarumscuticociliatosis

“…Furthermore, the quantitative PCR (qPCR) approach employed by Hewson et al (2023) may not be accessible to labs without qPCR instruments, and the cost of reagents and fluorophore tagged primers may prohibit broad application of this approach. Since the 2022 Caribbean mortality event, additional mass mortalities have been described in other geographic regions and in related Diadema species (Zirler et al 2023). To enable simple and specific detection of the DaSc-associated Philaster clade for diagnostic purposes, here we report a new PCR primer and amplification protocol that selectively amplifies the DaSc-associated Philaster .…”