Variations in the microalgal structure in paddy soil in Osaka, Japan: comparison between surface and subsurface soils |
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Authors: | Yuko Fujita Hiroyuki Nakahara |
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Institution: | (1) Lake Biwa Museum, Oroshimo 1091, Kusatsu, Shiga 525-0001, Japan;(2) Department of Natural Resources, Graduate School of Global Environmental Studies, Kyoto University, Kyoto, Japan |
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Abstract: | Seasonal variations in microalgal communities were compared between surface and subsurface paddy soils in Osaka, Japan. Soil
samples were collected from depths of 0–1 (surface), 8–9, and 17–18 cm. Diatom cells were counted directly, and the numbers
of other microalgae were estimated using a culture method. The microalgal community as well as the soil properties changed
drastically in the surface soil as a consequence of alternate flooding and drainage. In the soil collected at a depth of 0–1
cm, the cell density of diatoms and the viable count of other microalgae markedly increased, and Chlorella spp., Nitzschia spp., and Navicula spp. were predominant during the flooding period, whereas Scenedesmus spp. and Hantzschia spp. were predominant during the drainage period. In contrast, in the soils collected at depths of 8–9 and 17–18 cm, the
cell density of diatoms and the viable count of other microalgae remained constant. Despite the unavailability of light, a
large number of microalgae were present in these subsurface soils throughout the annual cultivation cycle, and Scenedesmus spp. and Nitzschia spp. were always dominant. Cyanophytes were also present at all the depths but had low relative frequencies. These results
suggest that the algae that are predominant in paddy soil can survive not only drastic changes in water content but also complete
darkness. |
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Keywords: | Seasonal variation Microalgae Surface paddy soil Subsurface paddy soil |
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