Field Science Center, Graduate School of Agricultural Science, Tohoku University
Abstract
As a case study, the seasonal changes of diatom community in flooded water of paddy fields were discussed. The investigations were conducted on Andosols (Field 1) at Field Science Center, Tohoku University, and on Fluvisols (Field 2) at Furukawa Agricultural Experimental Station, located at Miyagi Prefecture, Japan, during the rice-growing season of 2004. The results obtained are as follows: 1) Diatom cell density at Field 1 ranged between 2.1x10^5 and 1.1x10^6 cells L^. There was no large difference during the experimental period in Field 1. Diatom cell density in Field 2 ranged between 4.3x10^5 and 5.3x10^6 cells L^. Diatoms in Field 2 were low in the end of May, and increased gradually thereafter. 2) Nineteen genera were observed in Field 1 and twenty-four genera in Field 2. In general, Nitzschia was predominated genus in the both fields. In Field 1, Melosira became predominated from June to August. In Field 2, Navicula was also predominated in July
