Abstract
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-nitzschiamultiseries during 1992–1993, 2002, and a shift towards the dominance of Pseudo-nitzschiamultistriata and Pseudo-nitzschiacalliantha 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-nitzschiamultiseries 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.
Highlights
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
Extensive datasets of long-term variations in the density of phytoplankton, including species belonging to the genus Pseudo-nitzschia from different areas, were studied to document the temporal variations in phytoplankton communities associated with environmental factors and climate change events [2,3,4,5,6]
A quite strong negative correlation between the density and the concentration of ammonium nitrogen in water was recorded for Pseudo-nitzchia calliantha (r = −0.691, p = 0.0005), which supports the data reported by a number of authors that the increase in Pseudo-nitzschia abundance seems to be a response to eutrophication [2,32,33,34]
Summary
Long-term series of observations on changes in dominant diatoms of the genus Pseudo-nitzschia are crucial for understanding the potential threat of toxic blooms and their effects. Diatoms of the genus Pseudo-nitzschia are a dominant group of toxic plankton microalgae in the northwestern Sea of Japan, constituting up to 75–98% of the total phytoplankton density in bloom seasons [11,12]. Extensive datasets on species and genetic diversity, certain bloom events, and domoic acid concentration in cultures of the dominant Pseudo-nitzschia species isolated from the northwestern Sea of Japan were accumulated over the past.
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