Abstract. Upon enrichment with lithium 385.6 μM Li, culture of Pseudo-nitzschia multiseries Hasle produces substantially higher level of the neurotoxin domoic acid DA 230 fg · cell-1 than the control 135 fg · cell-1. We hypothesize that in Cardigan Bay, where the first domoic acid episode was reported, high levels of Li could have originated via a massive freshwater run-off involving an adjacent dump. Lithium enrichment may have played a part in enhancing DA production leading to the intoxication episodes of 1987. Thus, anthropogenic activities may play a role as a sustainer of algal blooms and should be included in habitat management considerations involving coastal and inshore algal blooms, both toxigenic and non-toxigenic.