1. 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, pregledni znanstveni članek Povzetek: 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.
Ključne besede: Adriatic, Pseudo-nitzschia, diversity, ecology
Objavljeno v DiRROS: 14.04.2025; Ogledov: 321; Prenosov: 138
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2. Toxicity of the Diatom Genus Pseudo-nitzschia (Bacillariophyceae) : insights from toxicity tests and genetic screening in the Northern Adriatic SeaTimotej Turk Dermastia, Sonia Dall’Ara, Jožica Dolenc, Patricija Mozetič, 2022, izvirni znanstveni članek Povzetek: Diatoms of the genus Pseudo-nitzschia H.Peragallo are known to produce domoic acid (DA), a toxin involved in amnesic shellfish poisoning (ASP). Strains of the same species are often classified as both toxic and nontoxic, and it is largely unknown whether this difference is also genetic. In the Northern Adriatic Sea, there are virtually no cases of ASP, but DA occasionally occurs in shellfish samples. So far, three species—P. delicatissima (Cleve) Heiden, P. multistriata (H. Takano) H. Takano, and P. calliantha Lundholm, Moestrup, & Hasle—have been identified as producers of DA in the Adriatic Sea. By means of enzme-linked immunosorbent assay (ELISA), high-performance liquid chromatography with UV and visible spectrum detection (HPLC-UV/VIS), and liquid chromatography with tandem mass spectrometry (LC-MS/MS), we reconfirmed the presence of DA in P. multistriata and P. delicatissima and detect for the first time in the Adriatic Sea DA in P. galaxiae Lundholm, & Moestrup. Furthermore, we attempted to answer the question of the distribution of DA production among Pseudo-nitzschia species and strains by sequencing the internal transcribed spacer (ITS) phylogenetic marker and the dabA DA biosynthesis gene and coupling this with toxicity data. Results show that all subclades of the Pseudo-nitzschia genus contain toxic species and that toxicity appears to be strain dependent, often with geographic partitioning. Amplification of dabA was successful only in toxic strains of P. multistriata and the presence of the genetic architecture for DA production in non-toxic strains was thus not confirmed.
Ključne besede: Adriatic, dabA, domoic acid, Pseudo-nitzschia galaxiae
Objavljeno v DiRROS: 16.07.2024; Ogledov: 659; Prenosov: 361
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3. Evaluation of the rbcL marker for metabarcoding of marine diatoms and inference of population structure of selected generaTimotej Turk Dermastia, Ivano Vascotto, Janja Francé, David Stanković, Patricija Mozetič, 2023, izvirni znanstveni članek Povzetek: Diatoms are one of the most important phytoplankton groups in the world’s oceans. There are responsible for up to 40% of the photosynthetic activity in the Ocean, and they play an important role in the silicon and carbon cycles by decoupling carbon from atmospheric interactions through sinking and export. These processes are strongly influenced by the taxonomic composition of diatom assemblages. Traditionally, these have been assessed using microscopy, which in some cases is not reliable or reproducible. Next-generation sequencing enabled us to study diversity in a high-throughput manner and uncover new distribution patterns and diversity. However, phylogenetic markers used for this purpose, such as various 18S rDNA regions, are often insufficient because they cannot distinguish between some taxa. In this work, we demonstrate the performance of the chloroplast-encoded rbcL marker for metabarcoding marine diatoms compared to microscopy and 18S-V9 metabarcoding using a series of monthly samples from the Gulf of Trieste (GoT), northern Adriatic Sea. We demonstrate that rbcL is able to detect more taxa compared to 18S-V9 metabarcoding or microscopy, while the overall structure of the diatom assemblage was comparable to the other two methods with some variations, that were taxon dependent. In total, 6 new genera and 22 new diatom species for the study region were identified. We were able to spot misidentification of genera obtained with microscopy such as Pseudo-nitzschia galaxiae, which was mistaken for Cylindrotheca closterium, as well as genera that were completely overlooked, such as Minidiscus and several genera from the Cymatosiraceae family. Furthermore, on the example of two well-studied genera in the region, namely Chaetoceros and particularly Pseudo-nitzschia, we show how the rbcL method can be used to infer even deeper phylogenetic and ecologically significant differences at the species population level. Despite a very thorough community analysis obtained by rbcL the incompleteness of reference databases was still evident, and we shed light on possible improvements. Our work has further implications for studies dealing with taxa distribution and population structure, as well as carbon and silica flux models and networks.
Ključne besede: rbcL, metabarcoding, monitoring, diatoms, population genetics, Pseudo-nitzschia, Adriatic
Objavljeno v DiRROS: 12.07.2024; Ogledov: 699; Prenosov: 365
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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, izvirni znanstveni članek Povzetek: 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.
Ključne besede: Pseudo-nitzschia, morphology, phylogeny, seasonality, time series, Adriatic Sea
Objavljeno v DiRROS: 18.03.2020; Ogledov: 3824; Prenosov: 1286
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