Effects of light quality on initiation and development of meroplanktonic diatom blooms in a eutrophic shallow sea |
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Authors: | Tomoyuki Shikata Atsushi Nukata Souta Yoshikawa Tadashi Matsubara Yasuhiro Yamasaki Yohei Shimasaki Yuji Oshima Tsuneo Honjo |
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Institution: | (1) Laboratory of Marine Environmental Science, Department of Bioscience and Biotechnology, Graduate School of Bioresource and Bioenvironmental Sciences, Kyushu University, 6-10-1, Hakozaki, Fukuoka 812-8581, Japan |
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Abstract: | We investigated the effects of light quality on resting stage cell germination and vegetative cell growth of meroplanktonic
diatoms in a small port in Hakata Bay, Japan and in the laboratory. During the investigation over the year of 2006, the meroplanktonic
diatom bloom first occurred in the end of May and then repeated wane and wax until October in the small port. From late April
to middle May, light penetrating the water column was often strong and attenuations of all spectral lights were low. During
this period, Skeletonema costatum, Thalassiosira minima, and Chaetoceros sp. appeared frequently, followed by the blooms of S. costatum and Chaetoceros sp. in late May. Thereafter, S. costatum and Chaetoceros sp. bloomed in late June but not in middle June, when pigmented flagellates bloom appeared. The attenuation of short-wavelength
light such as violet and blue lights was markedly high during these diatom and flagellate blooms; all blooms disappeared within
several days. Vegetative cell strains of the three diatoms under light emitting diodes (LEDs) with six different spectra (violet,
blue, green, orange, red, and near-infrared) grew at a higher rate under short-wavelength light, violet and blue. On the other
hand, when suspensions of bottom sediments from Hakata Bay were cultured under the same LEDs and in the dark, vegetative cells
of S. costatum appeared under all LEDs except for orange and near-infrared, vegetative cells of T. minima appeared under all LEDs but not in the dark, and vegetative cells of Chaetoceros sp. appeared under violet and blue LEDs. However, vegetative cell densities of the three diatoms increased much more under
violet light than under other LEDs within a short period (6 days). Our study indicates that underwater penetration by short-wavelength
light, such as violet and blue, may be an important factor in the initiation and development of meroplanktonic diatom blooms. |
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