Significance of attached cyanobacteria relevant to the occurrence of mustyodor in Lake Kasumigaura

The microorganisms and compounds causing musty odor in the second largest l ake in Japan, Lake Kasumigaura, where the water is used for drinking, fishe ries and agricultural purposes, were examined during the severe occurrence of musty odor in 1989 and 1990. This study was undertaken to determine the microorganisms arid their metabolites responsible for the musty odor. Phorm idium tenue, which has been reported to be the main contributor of the odor in Lake Kasumigaura, was isolated. Furthermore, four monoxenic strains of the odor producing attached cyanobacteria, Phormidium viscosum, Lyngbya all orgei, Oscillatoria splendida and Phormidium uncinatum, were isolated from submerged rocks and sediments in the lake. All of the four attached strains produced only geosmin, which was confirmed by gas chromatograph/mass spect rometer analysis, in the monoxenic cultures. In particular, we confirmed fo r the first time that P. viscosum, L. allorgei and P. uncinatum produced ge osmin. Both the planktonic Phormidium tenue, a well known 2-methylisoborneo l (MIB) producer and geosmin-producing attached cyanobacteria were closely associated with the occurrence of musty odor in Lake Kasumigaura. (C) 1998 Elsevier Science Ltd. All rights reserved.