1. Phytoplankton diversity in the Northern Adriatic Sea : insights and inconsistencies from microscopy and metabarcodingGiorgia Montali, Francesca Neri, Elisa Banchi, Federica Cerino, Timotej Turk Dermastia, Janja Francé, Patricija Mozetič, 2026, original scientific article Abstract: Phytoplankton plays a fundamental role in marine ecosystems and is widely used to assess environmental change. In this study, light microscopy and DNA metabarcoding approaches were used to investigate phytoplankton communities at three long-term monitoring sites in the northern Adriatic Sea. By combining the two approaches, more than 500 species were recorded. Metabarcoding detected substantially higher diversity, particularly among small and fragile organisms that are difficult to identify under a microscope, whereas microscopy was better for identifying larger species with distinctive morphology. Because species contain different amounts of genetic material, DNA data can overestimate or underestimate their true contribution to the community. Indeed, after applying correction factors that account for these differences, the DNA-based estimates became more consistent with the microscopy results for several phytoplankton groups. The differences among the samples were influenced more by the approach used than by the sampling location. Overall, combining these two approaches provides an accurate and robust picture of phytoplankton communities. In this way, it is possible to improve the reliability of marine biodiversity assessments and to support better environmental monitoring and management in coastal seas.
Keywords: phytoplankton, diversity, environmental DNA, Long-Term Ecological Research, amplicon sequencing, North Adriatic Sea
Published in DiRROS: 25.03.2026; Views: 274; Downloads: 201
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2. Microalgal communities in mucilage aggregates (Northern Adriatic Sea, summer 2024) based on microscopy and metabarcodingMarika Ubaldi, Francesca Neri, Giorgia Montali, Tiziana Romagnoli, Aurora Tomasini, Federica Cerino, Timotej Turk Dermastia, Patricija Mozetič, Janja Francé, Camilla Spoto, Stefano Accoroni, Cecilia Totti, 2026, original scientific article Abstract: The mucilage phenomenon consists of the appearance of large gelatinous aggregates floating in the water column. In summer 2024, this event has reappeared in the Northern Adriatic Sea (NAS) on a large scale. This study provides an integrated characterization of the microalgal community within mucilage aggregates and surrounding waters in two NAS areas (Gulf of Trieste and Conero Riviera) using light microscopy (LM), metabarcoding (MB) based on ribosomal 18S V4 and V9 markers, and scanning electron microscopy (SEM) for selected taxa identification. Mucilage aggregates acted as dynamic microbial hotspots, hosting a rich diatom community, with abundances 1–2 orders of magnitude higher than in the surrounding water. Dominant diatom species were Cylindrotheca closterium, Nitzschia spp., Nitzschia gobbii, and Thalassionema nitzschioides. Some phytoflagellates (e.g., Tetraselmis spp.) and dinoflagellates (e.g., Karlodinium veneficum, Pseliodinium fusus, and Wangodinium sinense) were detected exclusively by MB, while LM and SEM revealed species missed by other approaches. Gonyaulax fragilis, one of the species indicated as an important mucus producer, was present at the onset and throughout the phenomenon, as detected by LM and MB. The integrated approach improves knowledge of microalgal communities in NAS mucilage.
Keywords: mucilage, Northern Adriatic Sea, phytoplankton, microalgae, metabarcoding, microscopy, Gonyaulax fragilis, Harmful Algal Blooms
Published in DiRROS: 27.01.2026; Views: 412; Downloads: 333
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3. Comprehensive insights into Pseudo-nitzschia research in the Adriatic Sea : diverse perspectives and emerging discoveriesTimotej Turk Dermastia, Janja Francé, Jasna Arapov, Francesca Neri, Stefano Accoroni, Cecilia Totti, Federica Cerino, Maria Immacolata Ferrante, Fabrizio Bernardi Aubry, Stefania Finotto, Jelena Godrijan, Dragana Drakulović, Patricija Mozetič, 2025, review article Abstract: Pseudo-nitzschia, a globally distributed diatom genus, dominates phytoplankton communities in biomass and abundance, with some species producing domoic acid (DA), the neurotoxin responsible for Amnesic Shellfish Poisoning (ASP). The Adriatic Sea has become a hub of Pseudo-nitzschia research over the past 15 years. This review synthesizes multidisciplinary research across Adriatic sub-basins, integrating morphological, genetic, and ecological data. While ASP has never been documented in the Adriatic, DA was occasionally detected in shellfish. The production was linked to toxic species such as P. multistriata, P. calliantha, and P. galaxiae, which were found to produce DA in cultures from Adriatic isolates. Despite progress, LM-based monitoring remains prevalent, underestimating species complexity and toxigenic potential. Electron microscopy and genetic barcoding have nonetheless revealed new insights into the species composition of this genus in Adriatic. A total of 14 species have been reported so far with prominent regional disparity: the northern and middle Adriatic host higher diversity, contrasting with the southern Adriatic, where only five species were confirmed, and research remains sparse. Seasonal dynamics show summer-autumn peaks in abundance, though interannual and regional variability is notable. We present recent advances from the Adriatic including the discovery of Pseudo-nitzschia-infecting viruses, population genomic insights in P. multistriata, and metabarcoding-driven revelations of cryptic diversity. Finally, we highlight critical knowledge gaps, including the ecological drivers of toxicity and the impacts of oligotrophication on community shifts. Collaborative, high-resolution methodologies (e.g., omics, automated imaging) are urged to address emerging challenges under climate change and anthropogenic pressures.
Keywords: Adriatic, Pseudo-nitzschia, diversity, ecology
Published in DiRROS: 14.04.2025; Views: 1134; Downloads: 575
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4. Ecological time series and integrative taxonomy unveil seasonality and diversity of the toxic diatom Pseudo-nitzschia H. Peragallo in the northern Adriatic SeaTimotej Turk Dermastia, Federica Cerino, David Stanković, Janja Francé, Andreja Ramšak, Magda Tušek-Žnidarič, Alfred Beran, Vanessa Natali, Marina Cabrini, Patricija Mozetič, 2020, original scientific article Abstract: Pseudo-nitzschia H. Peragallo (1900) is a globally distributed genus of pennate diatoms that are important components of phytoplankton communities worldwide. Some members of the genus produce the neurotoxin domoic acid, so regular monitoring is in place. However, the identification of toxic members in routine samplings remains problematic. In this study, the diversity and seasonal occurrence of Pseudo-nitzschia species were investigated in the Gulf of Trieste, a shallow gulf in the northern Adriatic Sea. We used time series data from 2005 to 2018 to describe the seasonal and inter-annual occurrence of the genus in the area and its contribution to the phytoplankton community. On average, the genus accounted for about 15 % of total diatom abundance and peaked in spring and autumn, with occasional outbreaks during summer and large inter-annual fluctuations. Increased water temperature and decreased salinity positively affected the presence of some members of the genus, while strong effects could be masked by an unsuitable definition of the species complexes used for monitoring purposes. Therefore, combining morphological (TEM) and molecular analyses by sequencing the ITS, 28S and rbcL markers, eight species were identified from 83 isolated monoclonal strains: P. calliantha, P. fraudulenta, P. delicatissima, P. galaxiae, P. mannii, P. multistriata, P. pungens and P. subfraudulenta. A genetic comparison between the isolated strains and other strains in the Mediterranean was carried out and rbcL was inspected as a potential barcode marker in respect to our results. This is the first study in the Gulf of Trieste on Pseudo-nitzschia time series from a long-term ecological research (LTER) site coupled with molecular data. We show that meaningful ecological conclusions can be drawn by applying integrative methodology, as opposed to the approach that only considers species complexes. The results of this work will provide guidance for further monitoring efforts as well as research activities, including population genetics and genomics, associated with seasonal distribution and toxicity profiles.
Keywords: Pseudo-nitzschia, morphology, phylogeny, seasonality, time series, Adriatic Sea
Published in DiRROS: 18.03.2020; Views: 4921; Downloads: 1726
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