Changes in the photosynthetic activity of Microcystis colonies after gut passage through Nile tilapia (Oreochromis niloticus) and silver carp (Hypophthalmichthys molitrix)

The photosynthetic activity of cyanobacteria (predominantly Microcystis spp.) after passage through the digestive tract of Nile tilapia (Oreochromis niloticus) and silver carp (Hypophthalmichthys molitrix) was determined by CCD fluorescence imaging, using slow complementary area approach, during a 4-day cultivation of fish faeces in algal ZBB medium. The cyanobacteria colonies exhibited a 92-95% reduction in of activity (P < 0.001) after passage through Nile tilapia, whereas there was a significant (P < 0.01) stimulation of photosynthetic activity after passage through the silver carp gut.