Salinity, a climate-change factor affecting growth, domoic acid and isodomoic acid C content in the diatom Pseudo-nitzschia seriata (Bacillariophyceae)

ABSTRACT

Freshening of the oceans is a predicted outcome of climate change. Marine phytoplankton organisms are in general affected by salinity changes and, given their key role in oceanic food webs and geochemical cycles, it is important to investigate the response of phytoplankton species to salinity changes. Diatom species of the genus Pseudo-nitzschia can form massive and, at times, toxic blooms, because several Pseudo-nitzschia species produce the neurotoxin domoic acid. Domoic acid can cause amnesic shellfish poisoning in humans and harm animals in the marine food web. The species Pseudo-nitzschia seriata can produce domoic acid in cold-water areas, like the Arctic. Hence, it is relevant to investigate the response of P. seriata to different salinity levels. Three strains of P. seriata were exposed to four different salinity levels (15, 20, 30 and 40). None of the strains grew at salinity 15, and maximum growth rates were found at salinity 30. All three strains contained toxins at salinities 20–40, with the highest cellular content occurring at salinity 20. The peak in toxin content was related to a significantly lower growth rate. However, the higher toxin content overrode the lower growth rate, ultimately resulting in a higher toxin potential at salinity 20. In addition to domoic acid, all strains contained isodomoic acid C in surprisingly high amounts, similar to the domoic acid content.

KEYWORDS:

• Arctic
• Intraspecific variation
• Ocean freshening
• Toxicity

ACKNOWLEDGEMENTS

We thank Pearse McCarron [Certified Reference Material (CRM) programme of the NRC-IMB, Halifax, NS, Canada] for providing an analytical standard of isodomoic acid C; and Sara Harðardóttir for providing the phytoplankton samples from Iceland.

SUPPLEMENTARY MATERIAL

Supplemental data for this article can be accessed on the publisher’s website.

DISCLOSURE STATEMENT

No potential conflict of interest was reported by the author(s).

Additional information

Funding

Our work has been supported by the Ingeniør Svend G. Fiedler og Hustrus grant and the Independent Research Fund Denmark (grant 9040-00248B); it has also been partially supported by the Helmholtz-Gemeinschaft Deutscher Forschungszentren, through the research programme ‘Changing Earth – Sustaining our Future’ of the Alfred-Wegener-Institut Helmholtz-Zentrum für Polar- und Meeresforschung.