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.

拟菱形藻H. Peragallo（1900年）是羽状硅藻是全球浮游植物群落的重要组成部分的全球分布的属。该属的某些成员会产生神经毒素多摩酸，因此需要定期监控。但是，在常规采样中鉴定有毒成员仍然存在问题。在这项研究中，假性尼兹菌的多样性和季节发生在亚得里亚海北部的浅海湾的里雅斯特海湾，对这些物种进行了调查。我们使用2005年至2018年的时间序列数据来描述该属的季节性和年际发生情况及其对浮游植物群落的贡献。平均而言，该属约占硅藻总丰度的15％，并在春季和秋季达到峰值，夏季偶尔爆发，年际波动较大。水温升高和盐度降低积极地影响了该属某些成员的存在，而对监测所用物种复合物的不适当定义可能掩盖了强烈的影响。因此，通过对ITS，28S和rbcL进行测序，将形态学（TEM）和分子分析相结合：标记物，八个物种从83个分离的单克隆菌株鉴定P.衔，P. fraudulenta，P.柔弱，P. galaxiae，P. mannii，P. multistriata，P. pungens和P. subfraudulenta。在地中海地区分离的菌株与其他菌株之间进行了遗传比较，并针对我们的结果检查了rbcL作为潜在的条形码标记。这是在伪尼茨基亚的的里雅斯特湾进行的第一项研究来自长期生态研究（LTER）站点的时间序列以及分子数据。我们表明，与仅考虑物种复杂性的方法相反，通过应用综合方法学可以得出有意义的生态结论。这项工作的结果将为进一步监测工作以及与季节分布和毒性概况有关的研究活动（包括种群遗传学和基因组学）提供指导。