Water Blooms of Uroglena Americana and the Identification of Odorous Compounds

Since July 1980, a strong fishy odor in the Nunobiki Reservoir has been associated with water blooms of the alga Uroglenaamericana (Chrysophyceae). According to ecological studies, water blooms were formed hourly by vertical and horizontal accumulation. The movement of organisms was affected by weather conditions, including the amount of sunlight and the direction and velocity of the wind. To identify the odorous compounds, samples of this species were collected from water blooms by a plankton net. The odorous compounds were analyzed by gas chromatography mass spectrometry (GC-MS), nuclear magnetic resonance (NMR), and ultra-violet (UV) spectrometry. As a result, two odorous compounds, (E,E)-2,4-heptadienal and (E,Z)-2,4-heptadienal, were detected and identified.