Pseudo-nitzschia blooms associated with rapid onset of amnesic shellfish toxin contamination in mussels from Scottish coastal waters

Pseudo-nitzschia is present in the coastal waters around Scotland throughout the year and despite the frequent occurrence of blooms, shellfish contamination with domoic acid is relatively rare. However, in the summer of 2022, blooms led to unusually high levels of amnesic shellfish toxins in mussels at four sites, with the highest concentration of 95 mg kg-1 recorded in July at Braewick Voe. Pseudo-nitzschia australis was identified as the likely causative organism. Autumn blooms containing a mix of Pseudo-nitzschia species, including P. fraudulenta, occurred at some sites in the Shetland Islands in September, but were not associated with any toxicity. A regulatory monitoring programme is in place to safeguard public health, with no reported cases of human AST poisoning in the UK, although the potential for such an event exists.