however, that B12 concentrations in blooms were similar to non-bloom waters in roughly half of the samples collected, a fact possibly attributable to the time of sample collection as samples collected shortly after blooms vertically migrated to the surface would result in a shorten the time for C. polykrikoides to take up B12 and deplete the standing stock of this vitamin. In contrast, B1 concentrations during blooms were generally similar to non-bloom regions perhaps indicating that C. polykrikoides, a confirmed B1 auxotroph , was replete with regard to this vitamin. In fact, the higher carbon-specific vitamin B1 uptake rates outside the bloom compared to inside bloom patches indicates C. polykrikoides had a smaller vitamin demand than the nano- and microplankton in adjacent non-bloom regions.