2018 Volume 54 Issue 2 Pages 55-63
In Lake Hachiro, Akita, algal blooms occur every summer. Cyanobacteria such as Microcystis sp. and Anabaena sp. precipitate on the bottom sediments in autumn and overwinter. In this study, we carried out the recruitment experiments at 10℃, 15℃, and 20℃ using the bottom sediments collected in November 2016 in order to evaluate whether the precipitated cyanobacteria recruit from the sediments. While the amounts of recruited Microcystis cells tended to increase during the incubation of 10 days as the temperature increased from 10℃ to 20℃, Anabaena cells did not recruit at 20℃. In the sediment samples treated at 4℃ for 20 weeks, the amounts of recruited Microcystis and Anabaena cells at 20℃ were significantly larger than at 10℃. The low temperature treatment of sediment samples obviously promoted the recruitment of Anabaena cells, suggesting the importance of low water temperature in winter for germination and recruitment of Anabaena dormant cells. This study showed that the low temperature treatment of the sediments as well as setting of temperature condition was an important item for evaluating the recruitment of cyanobacteria from lake sediment samples.
