Growth Dynamics and Toxin Production of Pseudo-nitzschia Species Isolated from the Central Adriatic Sea

The marine diatoms <i>Pseudo-nitzschia</i> spp. are globally distributed primary producers, with certain species capable of producing neurotoxin domoic acid (DA), causing amnesic shellfish poisoning (ASP). This study investigates the toxicity and growth rates of <i>Pseudo-nitzschia</i> species isolated from aquaculture areas in the Central Adriatic Sea. A total of 54 strains from eight species were analysed, with strains originating from four different study sites. Growth rates and toxin production were examined across different growth phases in other species and strains. Most species, including <i>P. allochrona</i>, <i>P. calliantha</i>, <i>P. delicatissima</i>, <i>P. fraudulenta</i>, <i>P. galaxiae</i>, <i>P. mannii</i>, and <i>P. multistriata</i>, did not produce DA at any growth phase. The only species that showed toxin production, at 18 °C was <i>P. pseudodelicatissima</i> (0.0007-0.0250 pg cell^-1). Notably, the majority of <i>P. pseudodelicatissima</i> strains were toxic in the decay phase and some strains showed continuous toxin production throughout all growth phases. The highest growth rates for the analysed species were recorded in strains of <i>P. delicatissima,</i> which also exhibited the highest cell abundance (8.19 × 10⁵ cell mL^-1), followed by the species <i>P. allochrona</i>, <i>P. mannii</i> and <i>P. pseudodelicatissima.</i>