Abundance, spatial distribution and composition of resting stage cells of diatoms in bottom sediments of Harima-Nada and Osaka Bay, eastern Seto Inland Sea, Japan
2015
Imai, I. (Hokkaido University (Japan). Graduate School of Fisheries Sciences, Division of Marine Bioresource and Environmental Science, Plankton Laboratory) | Ishida, T. | Itakura, S. | Yamaguchi, M.
Spatial distributions of viable diatom resting stage cells (DRSC) in bottom sediments (top 3-cm depth) of Harima-Nada and Osaka Bay, eastern Seto Inland Sea, were investigated with the extinction dilution method (Most Probable Number (MPN) method) based on sediment incubation. The sampling cruise was carried out from June 13 to 16 in 2000. The dominant groups of DRSCs were composed of the species of the genera Chaetoceros, Thalassiosira and Skeletonema in sediment samples that ranged from ND (not detectable) to 1.3*10E5 MPN /cubic cm (mean 1.5*10E4), from ND to 1.7*10E5 MPN /cubic cm (mean 2.4*10E4), and from ND to 4.9*10E4 MPN /cubic cm wet sediment (mean 9.2*10E3), respectively. The densities of DRSCs of other dominant species were also enumerated on such as Skeletonema tropicum, Leptocylindrus danicus, Leptocylindrus minimus, Asterionellopsis glacialis, Thalassionema nitzschioides, Bacteriastrum hyalimum, Odontella longicruris and Stephanopyxis palmeriana. The total number of DRSCs reached a maximum value of 2.1*10E5 MPN /cubic cm wet sediment (mean 5.1*10E4). The DRSCs in bottom sediments generally distributed more abundantly at the coasts of Harima-Nada where more frequent diatom blooms have occurred than offshore areas showing lower densities of DRSCs. The most dominant diatom genus was Thalassiosira, followed by Chaetoceros and Skeletonema. The previous investigation in 1993 revealed the dominance of Skeletonema resting cells in bottom sediments in the northern coast of Harima-Nada, but Skeletonema resting cells were not abundant in 2000, suggesting a change of water quality conditions from eutrophication to oligotrophication to significant degree.
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