First report of toxic cyanobacterial species in Ganga River.
Toxic Oscillatoria sp. RBD01 and Leptolyngbya sp. RBD05 were microcystin positive.
Extracellular release of microcystin in Ganga River was above WHO limit.
Statistical analysis showed seasonal variation between water parameters.
Oscillatoria sp. RBD01 showed strong correlation with phosphate and nitrate.