Sampling activities conducted in the Tyre Coast Nature Reserve, southern Lebanon, to study the marine annelid fauna of the area, allowed for the revision of the diversity of this group in Lebanon. We particularly focused on non-indigenous species (NIS), which were characterised from morphological and molecular points of view. A total of 116 taxa were collected; 10 species are reported here for the first time in the Mediterranean Sea, while 6 species with presumable Indo-Pacific affinity are likely new to science. Seventy-three taxa were native, while 43 taxa were NIS; among the latter, 24 species are reported for the first time in Lebanon. Molecular data were obtained for 28 NIS, representing the first data from the Mediterranean Sea for 23 of them. Non-indigenous annelids occurring along the coast of Lebanon mainly have Indo-Pacific affinity. However, molecular data highlighted inconsistencies between the sampled material and the sequences available in public repositories, suggesting the widespread occurrence of species complexes in these taxa. These results suggest that further research on Indo-Pacific annelids is needed to understand their diversity patterns and invasion pathways. Additionally, the large number of new records of annelids in Lebanese waters indicate that further studies are needed to explore their diversity in comparison with neighbouring Mediterranean regions.

The zooxanthellate jellyfish Cassiopea andromeda (Forsskål, 1775), a Lessepsian species increasingly common in the western and central Mediterranean Sea, was investigated here to assess its potential as a source of bioactive compounds from medusa specimens both collected in the wild (the harbor of Palermo, NW Sicily) and reared under laboratory-controlled conditions. A standardized extraction protocol was used to analyze the biochemical composition of the two sampled populations in terms of protein, lipid, and pigment contents, as well as for their relative concentrations of dinoflagellate symbionts. The total extracts and their fractions were also biochemically characterized and analyzed for their in vitro antioxidant activity to quantify differences in functional compounds between wild and reared jellyfish. The two populations were similar in terms of extract yield, but with substantial differences in biomass, the number of zooxanthellae, protein and lipid contents, and fatty acid composition. The hydroalcoholic extracts obtained from jellyfish grown under controlled conditions showed greater antioxidant activity due to the presence of a higher content of bioactive compounds compared to wild jellyfish. This study could be the basis for considering the sustainable breeding of this holobiont or other similar organisms as a source of valuable compounds that can be used in the food, nutraceutical, or pharmaceutical sectors.

Climate change affects marine ecosystems in multiple ways, including sea warming and changes in biological community structure and diversity. The Mediterranean Sea has emerged as one of the most vulnerable regions, also because of the diverse patterns of introduction of non‐native species. First recorded in the coastal waters of Cyprus in 1903, the Red Sea jellyfish Cassiopea andromeda (Forskål, 1775) is spreading its distribution and local abundance, posing questions on its potential ecological implications. Here we identified the thermal tolerance, habitat suitability, and potential distribution range of the C. andromeda polyps, a key life cycle stage responsible for asexual reproduction and population persistence. By laboratory‐controlled respirometric measurements, we assessed that the polyps of C. andromeda exhibit their optimal metabolic performances at high water temperatures, but they are tolerant to winter conditions across the Mediterranean basin. Combining experimental respiration measurements with modelling approaches enabled the definition of the species' fundamental thermal niche, with an optimal seawater temperature at 35.7°C and critical limits at 6.4°C (minimum) and 39°C (maximum). Trait‐based thermal habitat suitability maps indicated a future increase of favourable habitats for the species under warming conditions according to the Representative Concentration Pathways (RCP 4.5 and 8.5 for 2050) in Mediterranean coastal areas. In the context of climate change scenarios, the rise of seawater temperature may enable polyps to thrive across a wider geographic range, predicting a westward and northward enlargement of C. andromeda populations in the Mediterranean Sea.

Medusae of the genus Cassiopea are common components of tropical and subtropical coastlines globally. Despite the broad distribution of this benthic scyphozoan, much about their ecology remains poorly described. Here, we collected over 100 adult Cassiopea individuals from Panama, the eastern United States, Cuba, the Philippines, Italy and Australia to examine continuity and differences in their diet across space, and to investigate whether their unique lifestyle is reflected in their diet. We found the majority of prey items to be associated with the epibenthos. The recovered prey were supermajority crustaceans, mainly harpacticoid copepods, with pteropods, nematodes, and miscellaneous eggs common as secondary components. Within the gastrovascular cavity of a single medusa, we found up to 379 items. There was a limited relationship between medusa size and prey items. Location had an impact on gut content diversity and medusa size had a small impact on the number of taxa found within the gut. In some sites, prey were scarce or absent from all medusae sampled. Overall, we reaffirm the diet previously recorded for small medusae in Puerto Rico and show that similar components are common in large and small medusae from throughout the East and West Atlantic and the Philippines.

The Levantine Basin is the first region of the Mediterranean Sea to be impacted by climate warming and the arrival of non-indigenous species (NIS) via the Suez Canal. Although Levantine zooplankton has been studied previously, recent datasets capable of detecting the occurrence of new taxa, or shifts in community composition, especially in the easternmost part of the basin, are lacking. The present study provides updated information on zooplankton composition from Tyre (South Lebanon). In this study, the occurrence of two copepod families (Canuellidae, Longipediidae) and the first regional record of Facetotecta (Y-nauplii) are reported for the first time in the Levantine Basin. Additionally, although six Calanoida species were recorded as new to the Lebanese fauna, none can be attributed to Lessepsian NIS.