Advancing the Taxonomy of the Diatom Through an Integrative Study Conducted in the Central and Southeastern Adriatic Sea.

The marine diatom genus comprises cosmopolitan phytoplankton species commonly present in the Adriatic Sea. Species within the genus have been of significant concern because they produce domoic acid (DA), which can cause amnesic shellfish poisoning (ASP). In this study, we identified species along the Central and Southeastern Adriatic Sea, where monthly sampling carried out from February 2022 to February 2024 allowed for comprehensive species documentation. species cell cultures isolated from the study areas were morphologically and molecularly analysed. Morphological analyses were performed using a scanning electron microscope (FE-SEM/STEM), while molecular analyses were conducted, targeting the ITS1-5.8S-ITS2, LSU, and L regions, to confirm species identity. This integrative approach led to the identification of eight species: , , , , , , , and . Our findings underscore the value of a combined approach for reliable species identification and contribute to the development of genetic sequence databases that support the advancement of next-generation methods such as metabarcoding. This research emphasises the importance of combined morphological and molecular methods for the differentiation of the cryptic and pseudo-cryptic species.