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Abstract

Phytoplankton are unicellular photosynthetic organisms that occur in vast abundance in the world's oceans. This diverse group of algae is responsible for nearly half of the total global CO2 fixation and forms the base of the marine food web. However, some phytoplankton taxa produce toxins that can poison marine wildlife and humans. Mass occurrences of such toxic unicellular algae in the plankton occur periodically and are known as harmful algal blooms (see the first photo). For example, the toxic diatom Pseudo-nitzschia (see the second photo) regularly emerges in the Pacific. In 2015, this microalga formed the largest harmful algal bloom ever recorded, which stretched along nearly the entire coast from Alaska to Mexico and caused massive ecologic and economic damage (1). On page 1356 of this issue, Brunson et al. (2) describe the biosynthesis of the toxin domoic acid that is produced by this diatom.