The fishy-smelling water bloom of Uroglena americana (Chrysophyceae) was first observed at the Nunobiki Reservoir (Hyogo Prefecture) in 1980, and then successively in 1981, 1984, 1986 and 1987. This organism was collected and condensed by a plankton net (NXX 25) while blooming in June, 1986. The condensates were immediately steam-distilled, and the distillates were extracted with dichloromethane. The extracts were analysed by GC, GC-MS, and FT-1H-NMR. Two volatile constituents, (E, Z)-2, 4-heptadienal and (E, E)-2, 4-heptadienal were identified.
