Dynamics of photosynthetic activity of cyanobacteria after gut passage through crucian carp (Carassius auratus gibelio) and goldfish (Carassius auratus auratus)

The photosynthetic activity of cyanobacteria (predominantly Microcystis spp.) after passage through crucian fish and goldfish was determined by photo-PAM (pulse-amplitude-modulated) during a 17-day cultivation of fish faeces in filtered lake water. The Microcystis exhibited a significant reduction of activity after passage through both crucian carp and goldfish, whereas there was a significant stimulation of photosynthetic activity of diatom and green algae following the depressed cyanobacteria during cultivation. The mainly stimulated eukaryotic algae species were Fragilariaceae and Scenedesmus obliquus by microscopy. Our results provide experimental evidence that Microcystis is damaged by crucian carp and goldfish digestion. That may be useful as a complementary method for combating cyanobacterial blooms and utilizing them for crucian carp and goldfish nutrition.