Potential importance of diatom resting stage cells in the onset of bloom on the shelf of the East China Sea
2001
Ishikawa, A. (Mie Univ., Tsu (Japan). Faculty of Bioresources) | Yabushita, Y. | Furuya, K. | Masuda, T.
The ecological role of phytoplankton resting stage cells in initiating Phytoplankton blooms on the continental shelf of East China Sea was evaluated experimentally in the laboratory. Sediments were collected at seven PN stations from outer to inner shelf during the early spring bloom from 16 to 19 April, 1996. On the assumption that there is re-suspension of sediments in the upper layer of the water column, where environmental conditions for germination of resting cells are favorable, individual sediment samples were suspended and incubated in f/2 medium at 15degC, 170/micro mol m sup (-2) s sup(-1) n a 12hL:12hD cycle. After 5 days, the abundance of Chlorophyll ¿ in the culture was measured and the concentration of germinated phytoplankton taxa observed with a microscope. In addition, their growth rate over 5 to 6 days was also estimated. High chlorophyll a and growth rates were observed in these experiments. Using these data, we calculated the time required for the abundances of chlorophyll a in the cultures to reach integrated values found naturally through the water column at early spring time in 1996. Results showed that only 7-8 days would be sufficient for each culture. Major components of the phytoplankton which appeared in the cultures were diatoms, mainly Chaetoceros debilis. Our results indicate the potential importance of diatom resting stage cells in the onset of the spring bloom. Considering the oceanographic characteristics of the East China Sea, such as the remarkable mixing of water column in winter followed by a stratification in spring, it is highly possible that the resting stage cells on the shelf act as seeds for the bloom.
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