Revealing Hidden Pelagic BioDiversity: Confirmed Records of Holoplanktonic Molluscs in Lebanese Waters (Eastern Levantine Mediterranean Sea)

This study provides the first confirmed records of two holoplanktonic molluscs, the sea elephant Pterotrachea coronata Forsskål, 1775, and the pelagic nudibranch Phylliroe bucephala Lamarck, 1816, in Lebanese waters (eastern Levantine Mediterranean Sea), based on photographic and video evidence collected during marine biodiversity monitoring surveys off Byblos (Jbeil), northern Lebanon, within an area of interest for future designation as a Marine Protected Area in Lebanon. In addition, an unidentified pelagic Mollusca larva was documented, along with important new observational data on hydromedusae of the genus Aequorea Péron & Lesueur, 1810.

These findings validate previously unconfirmed reports and highlight the presence of specialized and elusive holoplanktonic Mollusca in the region. Their occurrence reflects the ecological richness of Lebanese pelagic ecosystems, the availability of gelatinous zooplankton prey, and the complexity of marine trophic interactions.

This work further underscores the importance of sustained marine monitoring and the growing role of citizen science as an effective tool for documenting marine biodiversity. It also emphasizes the need for strengthened conservation efforts, including the expansion of Marine Protected Areas, to enhance knowledge and protection of understudied pelagic biodiversity in the Levantine basin.