Document Type


Publication Date



Cyanotoxins are an emerging issue that Great Lakes’ scientists are conducting research on to determine occurrence, spatial and seasonal distribution, monitoring strategies and potential causes in Lake Ontario. Conditions necessary for blooms of Cyanobacteria exist along the shoreline of Lake Ontario. This is especially true in some embayments and rivers as levels of the nutrient phosphorus that stimulates the growth of Cyanobacteria is above New York State Department’s of Environmental Conservation guidelines. Monitoring in 2004 demonstrated that abundance of Cyanobacteria are indeed high in streams, embayments and the nearshore compared to offshore waters of southern Lake Ontario. Initial research suggests that microcystin production along the southern shoreline of Lake Ontario is minimal and well below WHO guidelines. However, production of the microcystin toxin often exceeds World Health Organization guidelines in inland lakes and may serve as a source to Lake Ontario. More information is required on the yearly variability of microcystin as wet and dry weather conditions appear to have affected the blooms of Cyanobacteria and the production of microcystin from year 2004 to year 2005 in both Lake Ontario and inland lakes. Vigilance by the general public utilizing the waters of Lake Ontario is still required. When visible blooms of algae are present at the surface, the general public and their animals should avoid contact with these waters.


Appeared in Great Lakes Research Review, Volume 7, 2006