有害・有毒微細藻類の光応答増殖

抄録

Harmful algal blooms likely occur in enclosed coastal regions and sometimes cause the toxification and/or mortality of marine organisms such as fish and shellfish. To understand the bloom dynamics of harmful algae, it is important to clarify the effects of light intensity on the algal growth. This paper reviews the techniques of photoirradiation and cultivation for analyses of algal growth and discusses the growth responces (light-responsive growth) of harmful algae to various light intensities. As natural light enters the water column, the red color and infrared range of the light are absorbed near the surface of oceanic waters; thus, blue light accounts for a large proportion of PAR (photosynthesis available radiation) penetrating into water. High-brightness white LED (light-emitting diode) is capable of simulating closely such light spectrum of natural PAR in oceanic water. I, along with co-workers, evaluated the light-responsive growth of the harmful species such as Ostreopsis sp. 1 by using a newly developed photoirradiation-culture system which has white LEDs as light source. Our results showed that these tested harmful algae are able to grow at low light intensities of 10⁰~10¹ µmol photons m^-2 s^-1 and even under a strong light of 10³ µmol photons m^-2 s^-1. The optimal light intensities for algal growth seem to be different among the species. This suggests that harmful algae may have divergent growth strategies in response to light intensity. I think that high-brightness white LEDs and a photoirradiation culture system equipped with them can be powerful tools for the understanding of the bloom dynamics of harmful algae.