Causative microorganisms for musty odor occurrence in the eutrophic Lake Kasumigaura

Abstract

The musty odor phenomenon in Lake Kasumigaura, Japan (a eutrophic lake that is used for various purposes, including water supply source) was examined. The causative microorganisms responsible for the production of the odor compounds, geosmin and/or 2-methylisoborneol (MIB), and the odor release mechanism were studied in vitro and in situ. The numbers of the filamentous P. tenue in the lake water column were closely correlated with the concentration of MIB, but not geosmin. The isolated monoxenic P. tenue in culture produced only MIB. Geosmin concentration was well correlated with the number of actinomycetes in the sediment. Forty isolates of actinomycetes from the sediment around the water supply intake tower produced both geosmin and MIB in culture. Furthermore, the average ratio of production of geosmin to MIB was 1.40–1.0. Actinomycetes in the sediment played an important role in geosmin production. We concluded that geosmin and MIB from actinomycetes in the sediment, and MIB from P. tenue in the water column were jointly responsible for the severe musty odor occurrence of the waters supply source at Lake Kasumigaura.