Monday September 15 2025, 11pm (CEST) 9am (NZST)

Hannah Greenhough^1,2, Craig Waugh¹, Roel van Ginkel¹, Joel Bowater¹, Gurmeet Kaur¹, Joy Oakly¹, Maxence Plouviez¹, Richard A. Ingebrigtsen¹, Johan Svenson¹, Andrew I Selwood¹, Kirsty F Smith¹, Chris M Brown², Julien Vignier¹, Nathan J Kenny², Anne Rolton¹

Alexandrium pacificum: From Ecological Challenge to Biomedical Opportunity

¹Cawthron Institute, 98 Halifax Street East, Nelson, 7010, New Zealand
²Department of Biochemistry Te Tari Matu Koiora, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand

Marine microalgal toxins present opportunities for drug discovery but also pose substantial risks to aquaculture and coastal environments. The dinoflagellate Alexandrium pacificum produces paralytic shellfish toxins (PSTs), highly potent blockers of voltage-gated ion channels and promising candidates for drug development. Their complex chemistry and limited natural availability have constrained wider application, but recent advances in large-scale cultivation of A. pacificum have enabled gram-scale production of gonyautoxins, providing new opportunities for pharmaceutical and research applications.
In parallel, A. pacificum blooms pose significant challenges to aquaculture. In Aotearoa New Zealand, harmful algal blooms impact the green-lipped mussel (Perna canaliculus), a species of high economic, ecological, and cultural value. Experimental exposures to A. pacificum showed that early life stages are particularly sensitive, with mussel sperm mortality, embryo lysis, and up to 85% reductions in larval development at cell concentrations found in natural blooms. Later stages exhibit impaired growth, reduced attachment, and stress responses involving oxidative damage and immune suppression. These effects are further compounded when blooms coincide with marine heatwaves, intensifying impacts on mussel survival and recruitment.
Together, these findings highlight the contrasting impacts of A. pacificum. On one hand, its toxins represent valuable pharmacological tools with potential to drive drug discovery and biomedical innovation. On the other, the same compounds and associated bloom events disrupt mussel development, compromise aquaculture production, and threaten the resilience of coastal ecosystems. Recognising both the opportunities and risks of A. pacificum is essential for realising the biomedical potential of PSTs while developing strategies to protect aquaculture and coastal ecosystems under future climate change.