Cyanobacterial Harmful Algal Blooms (CHABs) in lentic waterbodies are becoming increasingly common because of climate change, changes in water usage and eutrophication. This study provides observational evidence that CHAB formation in a small Ohio reservoir (Lake Hope) is associated with metalimnetic disturbance during the summer months. Disturbance via lotic interflow may result in the appearance of CHABs in lentic habitats, with cyanobacterial maxima in the metalimnion.