Distribution of vitamin B12, Pseudo-nitzschia and domoic acid in the Northwest Passage

The prevalence of Harmful Algal Blooms (HAB) is increasing worldwide. In the Arctic, the domoic acid (DA) producing diatom Pseudo-nitzschia is responsible for Amnesic Shellfish Poisoning events. While laboratory studies revealed vitamin B 12 auxotrophy in Pseudo-nitzschia , the link between vitamin B 12 distribution, Pseudo-nitzschia abundances and DA concentration is unknown. An expedition was conducted to the Arctic, in which samples for plankton biomass, dissolved (d) and particulate (p) B 12 , Pseudo-nitzschia and DA were collected. Multidimensional scaling showed a separation of the stations into three main clusters, primarily driven by dB 12 and pB 12 . dB 12 was lowest in the East, ranging from 0.02 to 2.46 pmol L -1 , and inversely correlated to Pseudo-nitzschia and DA. In contrast, pB 12 concentrations were highest in the East ranging from 0.02-0.6 pmol L -1 . The observed positive correlation of Pseudo-nitzschia with DA and pB 12 suggests a demand for this micronutrient by toxigenic species. Furthermore, the high DA: Pseudo-nitzschia ratio, an indicator for the toxicity of the Pseudo-nitzschia population, correlated negatively with dB 12 and pB 12 , suggesting that toxicity could be influenced by the availability of this vitamin. Together with the very low dB 12 concentrations measured, this study highlights the potential of vitamin B 12 as a limiting nutrient to artic phytoplankton populations in general and Pseudo-nitzschia in particular.