Pigment content of selected planktonic algae in response to simulated natural light fluctuations and a short photoperiod

The lipophilic photosynthetic pigments in Limnothrix redekei, Planktothrix agardhii (cyanobacteria), Stephanodiscus minutulus. Synedra, acus (diatoms) , Scenedesmus acuminatus, and Scenedesmus armatus (chlorophycean) all isola ted from an eutrophic lake were quantitatively determined by HPLC. The alga e were grown semi-continuously under nutrient sufficient conditions at 20 d egrees C at a 12/12 h light/dark cycle with constant irradiance or with sim ulated natural light fluctuations as well as at a 6/18 h light/dark cycle w ith constant irradiance, all at the same daily light exposure. The zeaxanthin and the myxoxanthophyll contents of cyanobacteria were not i nfluenced by fluctuating light, a short photoperiod or a different sampling time. The chlorophyll b/a ratio, the lutein/chlorophyll a ratio, and the n eoxanthin content of chlorophycean as well as the chlorophyll c/a and the f ucoxanthin/chlorophyll a ratio of diatoms were only slightly influenced by these factors. Therefore in some cases marker pigment contents and in other cases marker pigment/chlorophyll a ratios may be more useful for quantifyi ng the relative importance of different taxonomic groups in natural phytopl ankton. Simulated natural light fluctuations or the length of the photoperi od only slightly influenced the pigment content or the marker pigment/chlor ophyll a ratio.