“Seed bank” of coastal planktonic diatoms in bottom sediments of Hiroshima Bay, Seto Inland Sea, Japan |
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Authors: | S Itakura I Imai K Itoh |
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Institution: | (1) Red Tide Research Division, Nansei National Fisheries Research Institute, Ohno, Saeki, Hiroshima 739-04, Japan, JP;(2) Laboratory of Marine Microbiology, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto 606-01, Japan, JP;(3) Division of Environment Management, National Research Institute of Aquaculture, Nansei, Watarai, Mie 516-01, Japan, JP |
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Abstract: | Abundance and temporal distribution of viable (able to germinate) resting stage cells of planktonic diatoms in bottom sediments
have been investigated almost monthly during 1989 to 1992 in Hiroshima Bay, western part of Seto Inland Sea, Japan. The abundance
of viable resting stages in bottom sediments was enumerated with the extinction dilution method (most probable number method,
MPN). In bottom sediments of Hiroshima Bay, dominantly distributed species and/ or genera of the diatom resting stages were
Skeletonema costatum, Chaetoceros spp. and Thalassiosira spp. Viable resting stages of these diatoms were densely distributed on the orders of 103 to 106 (MPN g−1 wet sediments), and persisted in bottom sediments throughout the investigation period. Conversely, vegetative cells of these
diatoms fluctuated remarkably in the water column and disappeared sporadically. Survival of the resting stages in a collected
sediment sample was also determined with the MPN method, at different storage temperatures (5, 10, 15, 20, 25 °C). The survival
test demonstrated that the diatom resting stages could survive in the dark for several months or years in sediments. Resting
stages survived longer at the lower storage temperature, and the order of longevity was consistent within three diatoms (Chaetoceros spp. > Thalassiosira spp. > S. costatum) at each storage temperature. The present study suggests that these diatom resting stages in the coastal bottom sediments
could serve as a “seed bank”, analogous to those of terrestrial plants. The seed bank would ensure the survival of diatoms
within highly fluctuating coastal environments, while it would also be the source of sporadic and autochthonous diatom blooms
in coastal waters.
Received: 29 November 1996 / Accepted: 16 December 1996 |
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