Many waterbodies across Nova Scotia (Canada) have been experiencing algal blooms occurring in large numbers and diversity, without knowledge or understanding about their causes and effects. Algal blooms have appeared in Mattatall Lake (ML) and other lakes of the province in recent years. ML experienced severe algal blooms in 2013. During the fall of 2014, massive algal blooms appeared in ML, and persisted until late December 2014. The blooms have a pattern of being nontoxic in the summer and potentially toxic in the fall-winter season, with nutrients increasing on a monthly basis.