Not So Toxic: Antarctic Pseudo-nitzschia Isolates Give Domoic Acid the Cold Shoulder.
When you think of harmful algal species, the icy waters of McMurdo Sound in Antarctica may not immediately come to mind. Yet, even in these icy waters, microscopic players like Pseudo-nitzschia—a genus of diatoms—are part of the story. This genus is renowned for its potential to produce domoic acid (DA), a neurotoxin responsible for amnesic shellfish poisoning. But what role does it play in Antarctic waters?
In a recent study, we assessed if Pseudo-nitzschia was present in McMurdo Sound, Antarctica. We used environmental DNA (eDNA) metabarcoding and chemical analysis to uncover more about their presence and potential toxicity in the region.
Symptoms and signs of Amnesic Shellfish Poisoning (ASP) caused by domoic acid (DA) toxicity in humans and DA toxicity symptoms in marine organisms. Illustration - Jacqui Stuart
Did We Find Pseudo-nitzschia?
We did find Pseudo-nitzschia species! Over several years of sampling, one species of this microalgae (Pseudo-nitzschia subcurvata) was the species detected the most, appearing at multiple sites over multiple years. Another species (Pseudo-nitzschia seriata) was also present in the area, adding to our understanding of Antarctic diatom diversity.
Left: Area where we got our samples for this study. Right: Where we detected Pseudo-nitzschia (orange dots)
Did We Find Toxic Pseudo-nitzschia?
No, none of the Pseudo-nitzschia cultures we grew produced the toxins we were looking for! To see if these species produce DA (the toxic stuff), we established 17 cultures from field samples. Culturing is when you grow single species of microalgae in a controlled laboratory environment. We screened all the cultures for DA and its isomers using advanced liquid chromatography-tandem mass spectrometry and did not detected any. While this finding aligns with other observations that most Antarctic Pseudo-nitzschia species are non-toxic, it’s important to note that this study represents just a small snapshot of a vast geographical area.
Left: Collecting microalgae samples for culturing. Right: Microalgal cultures growing in the laboratory at the Cawthron Institute. Images - Jacqui Stuart
Why Does This Matter?
Though none of these microalgae cultures had the toxins we were looking for, this study only scratches the surface of what’s happening in Antarctic waters. The oceans surrounding the Antarctic continent are vast, and this research covered just a small fraction of the Ross Sea Region. It doesn’t mean we’re out of the woods just yet, so to speak. Domoic acid, while undetected here, can have significant effects on fish, bird, and mammal health. In other parts of the world, toxins like these have caused major disruptions in marine food webs.
For Antarctica, monitoring species like Pseudo-nitzschia is vital—not just for the health of the ecosystem but also for iconic species like penguins and seals, which already face numerous environmental challenges. The last thing these animals need is an additional stressor in their already precarious habitats.
This work underscores the importance of ongoing monitoring in polar regions, particularly as climate change continues to reshape these environments. Understanding these microbial communities and their potential impacts helps us piece together the puzzle of how polar ecosystems function—and how they might change in the future.
If you'd like all the details, you can read the full article in Harmful Algae News Issue #77.
Who Contributed to This Research?
This research would not have been possible without the collective mahi of the following researchers:
Jacqui Stuart (Antarctic Research Centre & Cawthron Institute), Kirsty Smith, Lesley Rhodes, J. Sam Murray, & Emillie Passfield (Cawthron Institute), Tomohiro NISHIMURA (Cawthron Institute & Japan Fisheries Research and Education Agency), Dr Natalie Robinson (Antarctic Research Centre & NIWA) and Ken Ryan (Victoria University of Wellington).
