Formation mechanism and environmental drivers of Alexandrium catenella bloom events in the coastal waters of Qinhuangdao, China

• Published in: Environmental pollution (1987) 2022-11, Vol.313, p.120241-120241, Article 120241
• Main Authors: Wu, Hai-Yan, Dong, Chen-Fan, Zheng, Guan-Chao, Zhang, Zhi-Hua, Zhang, Ya-Ya, Tan, Zhi-Jun, Gu, Hai-Feng
• Format: Article
• Language: English
• Subjects: Alexandrium catenella; Biotransformation; Mussel; Paralytic shellfish toxin
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2022.120241

In the last 5 years, paralytic shellfish toxins (PSTs) have been recurrently detected in mollusks farmed in the mussel culture area of Qinhuangdao city, along with the occurrence of toxic outbreaks linked to dinoflagellate species of the Alexandrium genus. To understand the formation mechanism and variation of these events, continuous and comprehensive PSTs monitoring was carried out between 2017 and 2020. Through the analysis of both phytoplankton and cysts via light microscopy and quantitative polymerase chain reaction, it was shown that Alexandrium catenella was responsible for the production of PSTs, which consisted mainly of gonyautoxins 1,4 (GTX1/4, 87%) and GTX2/3 (13%). During bloom events in 2019, mussels accumulated the highest PSTs value (929 μg STX di-HCl eq·kg−1) in conjunction with the peak of cell abundances, and toxin profiles were consistent with high distributions of GTX1/4, GTX2/3, and Neosaxitoxin. Toxin metabolites vary in different substances and mainly transferred to a stable proportion of α-epimer: β-epimers 3:1. The environmental drivers of Alexandrium blooms included the continuous rise of water temperature (>4 °C) and calm weather with low wind speed and no significant precipitation. By comparing toxin profiles and method sensitivity, it was found that dissolved toxins in seawater are more useful for early warning. These results have important implications for the effective monitoring and management of paralytic shellfish poisoning outbreaks. [Display omitted] •Five years of interannual variations of Alexandrium bloom were investigated.•Alexandrium catenella was identified from morphological data and identification of cyst.•PST transformations were recorded during small-scale blooms with low cell density.•Temperature and toxins dissolved in seawater are proposed as important indicators for monitoring.