Changes in the composition of photosynthetic pigments and cellular structure of the brown algae Fucus vesiculosus L. and F. serratus L. from the Barents Sea during a prolonged period of darkness

The effect of a prolonged absence of light on the photosynthetic pigment content and cell ultrastructure in Fucus vesiculosus L. and F. serratus L. from the Barents Sea was investigated during a 30-day experiment in summer and under natural conditions in winter (at the end of the polar night). With decreasing irradiance, the accumulation of photosynthetic pigments, mainly violaxanthin, occurred. In the absence of light, the contents and ratio of pigments remained unchanged. At the end of the experiment, the following changes occurred in the cellular ultrastructure: the disappearance of the stored substances and the change in the shape and compression of the physodes. Higher proportions of mitochondria in the cell and of cristae in the mitochondria are indicative of the enhancement of the respiration processes. No degradational changes were found in the tissues and cells of fucoids during prolonged periods of darkness. This suggests the possibility of their transition from photoautotrophy to endogenous nutrition.