Diatom aggregates composed of one to many chains of Pseudonitzschia ps
eudodelicatissima were abundant (up to 10% of the autotrophic biomass)
in high-nutrient open-ocean regions of both the equatorial Pacific an
d north Atlantic. The chains were connected at a central mass composed
of fecal material. The morphology is consistent with viable diatoms g
rowing on or from eroding fecal pellets.