This review aimed to summarize original and published data on the bloom events caused by toxic diatoms of the genus Pseudo-nitzschia and to assess long-term variations in the composition of bloom-forming species in the northwestern Sea of Japan during 1992−2015. This information is crucial to understanding the potential threat of toxic blooms and their effects. A change in species composition was observed within the genus Pseudo-nitzschia: it was dominated by Pseudo-nitzschia multiseries during

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... 1992–1993, 2002, and a shift towards the dominance of Pseudo-nitzschia multistriata and Pseudo-nitzschia calliantha occurred in 2005–2015. We assume that the increased sea surface temperature recorded from Amursky Bay in the period of 1998–2009 compared to the data of 1980–1989 might be one of the causative factors for the shift observed. The absence of highly toxic Pseudo-nitzschia multiseries among the bloom-forming species is considered as one of the possible explanations for the lack of damage from the blooms of Pseudo-nitzschia over the past 15 years in the study area.