Comparative study for the effects of variable nutrient conditions on the biodegradation of microcystin-LR and concurrent dynamics in microcystin-degrading gene abundance

► Microcystin-LR (MCLR) degradation under different nutrient conditions was probed. ► Low nitrate amount causes increased degradation and fast-growing mlrA abundance. ► Decreased biodegradation with other nutrients correlates to inhibited mlrA abundance. ► MCLR-degradation may thus largely depend on responsible bacterial population. ► The population of responsible bacteria relates to that of other bacteria in biofilm.