Introduction to plankton researches using the Okazaki Large Spectrograph

Abstract

The Okazaki Large Spectrograph (OLS), built in 1980 at the National Institute for Basic Biology（Okazaki, Japan）as a cooperative research facility, has been used for active spectroscopical studies by visiting scientists inside and outside countries. The OLS can project a wavelength spectrum from 250 nm (UV) to 1,000 nm (IR) onto horseshoe-shaped focal curve (10 m long), and irradiate different samples simultaneously. On the focal curve, the photon flux density of monochromatic light is 80 µmol m^-2 s^-1 at 300 nm and 160 µmol m^-2 s^-1 at 600 and at 900 nm, which is more than twice as much as that of the corresponding monochromatic component of tropical sunlight at noon. Recently, studies on photo-germination of resting stage cells in diatoms and phase-shift of diel vertical migration rhythm in red-tide flagellates have been conducted using the OLS. We believe that our facility can be used to clarify mechanisms of various photobiological responses in plankton.