Photosynthetic Activity of Dominant Algal Species in Eutrophic Shallow Lake (Großer Müggelsee, Berlin) Investigated by Microautoradiography

The photosynthetic activity of dominant phytoplankton in eutrophic shallow lake was investigated by the autoradiographic method in 1979 and 1980. It was shown by light and dark field microscopy that all species of Cyanophyta ( Oscillatoria redekei, Oscillatoria agardhii, Aphanizomenon flos‐aquae ) were characterized by a continuously high uptake of NaH 14 CO 3 . Similarly high photosynthetic activity was observed during the occurrence of Cryptomonas sp. and nanoplankton. Contrary to these observations, diatoms showed remarkably high portions of photosynthetically inactive biomass when their development was abundant. The reasons for this discrepancy between high biomass of diatoms and relatively low primary production (measured by the 14 C‐method and autoradiography) are discussed.