Daily oscillation of fatty acids and malondialdehyde in the dinoflagellate Lingulodinium polyedrum

The levels of the fatty acids, cis eicosahexenoic acid and cis linolenic acid, as well as the extent of lipoperoxidation, measured as malondialdehyde (MDA), were analyzed in the photosynthetic marine dinoflagellate Lingulodinium polyedrum at different times during the light: dark (L: D) cycle. Levels of MDA were twice as high during the day phase than during the night phase. This may be related to the circadian rhythm in photosynthesis as during photosynthetic electron flux, electrons can 'leak' and react with molecular oxygen producing reactive oxygen species (ROS) which in turn react with lipids, proteins, and DNA among other biomolecules. Fatty acid levels were highest during the day phase. Our findings indicate that unsaturated fatty acids are more susceptible to attack and degradation when L. polyedrum is exposed to light and that the cells compensate for this by an increased fatty acid content during the day. Excessive lipoperoxidation during the light phase could result in a higher level of chloroplast or plasma membrane disruption leading to cell death.