Abstract

Growth and potential photosynthetic activity of cyanobacteria (predominantly Microcystis spp.) passed through intestine of crucian carp and koi carp were compared with those of phytoplankton taken directly from lake during a 9 day cultivation of fish faeces in algal BG-11 medium. The cyanobacteria exhibited a significant reduction of activity in both maximum optical quantum yield (F_v/F_m) (P<0.001) and non-photochemical quenching value (NPQ) (P<0.001) after passage through the experimental cyprinid fishes. The difference in the photosynthetic activity of the cyanobacteria from crucian carp and koi carp faeces was not significant (P>0.05) for all the measurement intervals. The results provide experimental evidence that Microcystis can be damaged by crucian carp and koi carp digestion. That may be a complementary method using bio-manipulation to control cyanobacterial blooms.

Key words: Microcystis colonies, photosynthetic activity, crucian carp, koi carp, gut passage.