Abstract
It is estimated that diatoms perform photosynthesis corresponding about 20% of the global annual primary production. Therefore, diatoms contribute greatly to the global carbon cycle and hence to the regulation of the global climate. Toward the precise understanding of light-acclimation mechanisms in diatoms, we investigated the composition changes in their photosynthetic systems and photosynthetic pigments under different growth irradiances using a centric marine diatom, Chaetoceros gracilis, and a pennate marine diatom, Phaeodactylum tricornutum.
The molar ratio of accessory pigments to chlorophyll a stayed almost constant under a wide range of irradiance indicating their large antenna size. The relative amount of xanthophyll cycle pigments increased under high light, which would facilitate the effective protection mechanisms of photosystems under high light. The ratio of photosystem I to photosystem II, when grown in high-light, increased in C. gracilis but decreased in P. tricornutum. Divergent strategies among diatoms against the environmental light condition will be discussed.
