Photosynthetic rhythms in epipelic algal populations

Laboratory studies using freshwater and intertidal epipelic algal populations have shown that the vertical-migration rhythm displayed by the populations is in phase with a rhythmic change in the photosynthetic capacity. These rhythms are diurnal for freshwater algae and tidal superimposed on diurnal for intertidal algae. Maxima of cell emergence and photosynthetic capacity are coincident but the increase in photosynthetic capacity precedes cell emergence. Decreasing photosynthetic capacity occurs at a constant light intensity, increasing photosynthetic capacity occurs both in the light and the dark. These changes are thought to reflect changes in rate of the light reactions of photosynthesis.