| Effect of light and sediment grain size on the vertical migration of benthic diatoms
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| Guo Ying Du1, Jung Hyun Oak2, Hongbo Li3 and Ik Kyo Chung4,*
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1College of Marine Life Science, Ocean University of China, Qingdao 266003, China
2Marine Research Institute, Pusan National University, Busan 609-735, Korea
3National Marine Environmental Monitoring Center, Dalian 100623, China
4Division of Earth Environmental System, Pusan National University, Busan 609-735, Korea
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| ABSTRACT |
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Using chlorophyll fluorescence, the vertical migration of benthic diatoms responding to light intensity and affected by sediment grain size was studied. Minimal fluorescence (Fo) of surface sediment was measured by imaging pulse amplitude modulated (Imaging-PAM) fluorometer, and used to monitor diatom biomass variation in surface sediments. The test diatoms, Amphora coffeaeformis (C. Agardh) Kutzing and Cylindrotheca closterium (Ehrenberg) Reimann & Lewin, migrated to the sediment surface under irradiance from 50 to 500 μmol photons m-2 s-1. However, the diatoms exhibited no evident increase of surface biomass under dark conditions, and even showed slightly decrease of surface biomass under irradiances over 1,000 μmol photons m-2 s-1. The light intensity inducing the maximum surface migration of A. coffeaeformis was 100 μmol photons m-2 s-1, while the light intensity producing the same effect for C. closterium was 250 μmol photons m-2 s-1. C. closterium showed higher motility than A. coffeaeformis. Faster diatom surfacing was observed in larger grain size sediments (125-335 μm) than smaller ones (63-125 μm). This study confirmed the significant influence of light as a main triggering factor behind migration, indicated the distinct effect of different sediment grain size, and highlighted the species-specific migratory ability.
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| Key words:
benthic diatom; chlorophyll fluorescence; phototaxis; pulse amplitude modulated; vertical migration |
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