State Transition of Musty-odor-producing Cyanobacteria and 2-Methylisoborneol in the Serikawa Dam Reservoir

Abstract

In October 2014, a high concentration of 2-methylisoborneol MIB was confi rmed in the Serikawa dam reservoir because the concentration of musty-odor-producing cyanobacteria had increased. Therefore, serious off-fl avor problems with the drinking water occurred in Oita city located downstream of the reservoir. We investigated the species that had the potential to produce musty/earthly odor compounds by genetic analysis, and determined them to be Pseudanabaena limnetica and Pseudanabaena galeata. After the autumn thermal destratifi cation in the reservoir, the MIB concentration in the reservoir rapidly decreased. We considered that it was caused by biodegradation and analyzed the water in the reservoir by next-generation sequencing NGS. The results showed changes in the bacterial community composition around the time of the autumn thermal destratifi cation in the reservoir. The cyanobacteria survived in the low-temperature environment of a water temperature less than 10 and then showed an increase and high MIB-producing ability when the temperature reached 15. We hypothesize that the onset of biodegradation has an optimal temperature.